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[Maria-developers] Progress (by Knielsen): Store in binlog text of statements that caused RBR events (47)
by worklog-noreply＠askmonty.org 25 May '10

25 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Store in binlog text of statements that caused RBR events CREATION DATE..: Sat, 15 Aug 2009, 23:48 SUPERVISOR.....: Monty IMPLEMENTOR....: COPIES TO......: Knielsen, Serg CATEGORY.......: Server-Sprint TASK ID........: 47 (http://askmonty.org/worklog/?tid=47) VERSION........: Server-9.x STATUS.........: Code-Review PRIORITY.......: 60 WORKED HOURS...: 31 ESTIMATE.......: 4 (hours remain) ORIG. ESTIMATE.: 35 PROGRESS NOTES: -=-=(Knielsen - Tue, 25 May 2010, 08:29)=-=- Help debug strange problem in mysqlbinlog.test. Worked 1 hour and estimate 4 hours remain (original estimate unchanged). -=-=(Knielsen - Mon, 17 May 2010, 08:45)=-=- Merge with latest trunk and run Buildbot tests. Worked 1 hour and estimate 5 hours remain (original estimate unchanged). -=-=(Knielsen - Wed, 05 May 2010, 13:53)=-=- Review of fixes to first review done. No new issues found. Worked 2 hours and estimate 6 hours remain (original estimate unchanged). -=-=(Knielsen - Fri, 23 Apr 2010, 12:51)=-=- Status updated. --- /tmp/wklog.47.old.28747 2010-04-23 12:51:36.000000000 +0000 +++ /tmp/wklog.47.new.28747 2010-04-23 12:51:36.000000000 +0000 @@ -1 +1 @@ -In-Progress +Code-Review -=-=(Knielsen - Tue, 06 Apr 2010, 15:26)=-=- Code review (mailed to maria-developers@). Worked 7 hours and estimate 8 hours remain (original estimate unchanged). -=-=(Knielsen - Tue, 06 Apr 2010, 15:25)=-=- Status updated. --- /tmp/wklog.47.old.12734 2010-04-06 15:25:54.000000000 +0000 +++ /tmp/wklog.47.new.12734 2010-04-06 15:25:54.000000000 +0000 @@ -1 +1 @@ -Code-Review +In-Progress -=-=(Knielsen - Mon, 29 Mar 2010, 10:59)=-=- Status updated. --- /tmp/wklog.47.old.27790 2010-03-29 10:59:53.000000000 +0000 +++ /tmp/wklog.47.new.27790 2010-03-29 10:59:53.000000000 +0000 @@ -1 +1 @@ -In-Progress +Code-Review -=-=(Alexi - Thu, 18 Feb 2010, 19:29)=-=- Worked 20 hours (alexi) Worked 20 hours and estimate 15 hours remain (original estimate unchanged). -=-=(Serg - Fri, 05 Feb 2010, 14:04)=-=- Observers changed: Knielsen,Serg -=-=(Guest - Fri, 05 Feb 2010, 13:40)=-=- Category updated. --- /tmp/wklog.47.old.9197 2010-02-05 13:40:36.000000000 +0200 +++ /tmp/wklog.47.new.9197 2010-02-05 13:40:36.000000000 +0200 @@ -1 +1 @@ -Server-RawIdeaBin +Server-Sprint ------------------------------------------------------------ -=-=(View All Progress Notes, 31 total)=-=- http://askmonty.org/worklog/index.pl?tid=47&nolimit=1 DESCRIPTION: Store in binlog (and show in mysqlbinlog output) texts of statements that caused RBR events This is needed for (list from Monty): - Easier to understand why updates happened - Would make it easier to find out where in application things went wrong (as you can search for exact strings) - Allow one to filter things based on comments in the statement. The cost of this can be that the binlog will be approximately 2x in size (especially insert of big blob's would be a bit painful), so this should be an optional feature. HIGH-LEVEL SPECIFICATION: Content ~~~~~~~ 1. Annotate_rows_log_event 2. Server option: --binlog-annotate-rows-events 3. Server option: --replicate-annotate-rows-events 4. mysqlbinlog option: --print-annotate-rows-events 5. mysqlbinlog output 1. Annotate_rows_log_event [ ANNOTATE_ROWS_EVENT ] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Describes the query which caused the corresponding rows events. Has empty post-header and contains the query text in its data part. Example: ************************ ANNOTATE_ROWS_EVENT ************************ 00000220 | B6 A0 2C 4B | time_when = 1261215926 00000224 | 33 | event_type = 51 00000225 | 64 00 00 00 | server_id = 100 00000229 | 36 00 00 00 | event_len = 54 0000022D | 56 02 00 00 | log_pos = 00000256 00000231 | 00 00 | flags = <none> ------------------------ 00000233 | 49 4E 53 45 | query = "INSERT INTO t1 VALUES (1), (2), (3)" 00000237 | 52 54 20 49 | 0000023B | 4E 54 4F 20 | 0000023F | 74 31 20 56 | 00000243 | 41 4C 55 45 | 00000247 | 53 20 28 31 | 0000024B | 29 2C 20 28 | 0000024F | 32 29 2C 20 | 00000253 | 28 33 29 | ************************ In binary log, Annotate_rows event follows the (possible) 'BEGIN' Query event and precedes the first of Table map events which accompany the corresponding rows events. (See example in the "mysqlbinlog output" section below.) 2. Server option: --binlog-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tells the master to write Annotate_rows events to the binary log. * Variable Name: binlog_annotate_rows_events * Scope: Global & Session * Access Type: Dynamic * Data Type: bool * Default Value: OFF NOTE. Session values allows to annotate only some selected statements: ... SET SESSION binlog_annotate_rows_events=ON; ... statements to be annotated ... SET SESSION binlog_annotate_rows_events=OFF; ... statements not to be annotated ... 3. Server option: --replicate-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tells the slave to reproduce Annotate_rows events recieved from the master in its own binary log (sensible only in pair with log-slave-updates option). * Variable Name: replicate_annotate_rows_events * Scope: Global * Access Type: Read only * Data Type: bool * Default Value: OFF NOTE. Why do we additionally need this 'replicate' option? Why not to make the slave to reproduce this events when its binlog-annotate-rows-events global value is ON? Well, because, for example, we may want to configure the slave which should reproduce Annotate_rows events but has global binlog-annotate-rows-events = OFF meaning this to be the default value for the client threads (see also "How slave treats replicate-annotate-rows-events option" in LLD part). 4. mysqlbinlog option: --print-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ With this option, mysqlbinlog prints the content of Annotate_rows events (if the binary log does contain them). Without this option (i.e. by default), mysqlbinlog skips Annotate_rows events. 5. mysqlbinlog output ~~~~~~~~~~~~~~~~~~~~~ With --print-annotate-rows-events, mysqlbinlog outputs Annotate_rows events in a form like this: ... # at 1646 #091219 12:45:26 server id 100 end_log_pos 1714 Query thread_id=1 exec_time=0 error_code=0 SET TIMESTAMP=1261215926/*!*/; BEGIN /*!*/; # at 1714 # at 1812 # at 1853 # at 1894 # at 1938 #091219 12:45:26 server id 100 end_log_pos 1812 Query: `DELETE t1, t2 FROM t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.a=t2.a AND t2.a=t3.a` #091219 12:45:26 server id 100 end_log_pos 1853 Table_map: `test`.`t1` mapped to number 16 #091219 12:45:26 server id 100 end_log_pos 1894 Table_map: `test`.`t2` mapped to number 17 #091219 12:45:26 server id 100 end_log_pos 1938 Delete_rows: table id 16 #091219 12:45:26 server id 100 end_log_pos 1982 Delete_rows: table id 17 flags: STMT_END_F ... LOW-LEVEL DESIGN: Content ~~~~~~~ 1. Annotate_rows event number 2. Outline of Annotate_rows event behavior 3. How Master writes Annotate_rows events to the binary log 4. How slave treats replicate-annotate-rows-events option 5. How slave IO thread requests Annotate_rows events 6. How master executes the request 7. How slave SQL thread processes Annotate_rows events 8. General remarks 1. Annotate_rows event number ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To avoid possible event numbers conflict with MySQL/Sun, we leave a gap between the last MySQL event number and the Annotate_rows event number: enum Log_event_type { ... INCIDENT_EVENT= 26, // New MySQL event numbers are to be added here MYSQL_EVENTS_END, MARIA_EVENTS_BEGIN= 51, // New Maria event numbers start from here ANNOTATE_ROWS_EVENT= 51, ENUM_END_EVENT }; together with the corresponding extension of 'post_header_len' array in the Format description event. (This extension does not affect the compatibility of the binary log). Here is how Format description event looks like with this extension: ************************ FORMAT_DESCRIPTION_EVENT ************************ 00000004 | A1 A0 2C 4B | time_when = 1261215905 00000008 | 0F | event_type = 15 00000009 | 64 00 00 00 | server_id = 100 0000000D | 7F 00 00 00 | event_len = 127 00000011 | 83 00 00 00 | log_pos = 00000083 00000015 | 01 00 | flags = LOG_EVENT_BINLOG_IN_USE_F ------------------------ 00000017 | 04 00 | binlog_ver = 4 00000019 | 35 2E 32 2E | server_ver = 5.2.0-MariaDB-alpha-debug-log ..... ... 0000004B | A1 A0 2C 4B | time_created = 1261215905 0000004F | 13 | common_header_len = 19 ------------------------ post_header_len ------------------------ 00000050 | 38 | 56 - START_EVENT_V3 [1] ..... ... 00000069 | 02 | 2 - INCIDENT_EVENT [26] 0000006A | 00 | 0 - RESERVED [27] ..... ... 00000081 | 00 | 0 - RESERVED [50] 00000082 | 00 | 0 - ANNOTATE_ROWS_EVENT [51] ************************ 2. Outline of Annotate_rows event behavior ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Each Annotate_rows_log_event object has two private members describing the corresponding query: char *m_query_txt; uint m_query_len; When the object is created for writing to a binary log, this query is taken from 'thd' (for short, below we omit the 'Annotate_rows_log_event::' prefix as well as other implementation details): Annotate_rows_log_event(THD *thd) { m_query_txt = thd->query(); m_query_len = thd->query_length(); } When the object is read from a binary log, the query is taken from the buffer containing the binary log representation of the event (this buffer is allocated in Log_event object from which all Log events are derived): Annotate_rows_log_event(char *buf, uint event_len, Format_description_log_event *desc) { m_query_len = event_len - desc->common_header_len; m_query_txt = buf + desc->common_header_len; } The events are written to the binary log by the Log_event::write() member which calls virtual write_data_header() and write_data_body() members ("data header" and "post header" are synonym in replication terminology). In our case, data header is empty and data body is just the query: bool write_data_body(IO_CACHE *file) { return my_b_safe_write(file, (uchar*) m_query_txt, m_query_len); } Printing the event is just printing the query: void Annotate_rows_log_event::print(FILE *file, PRINT_EVENT_INFO *pinfo) { my_b_printf(&pinfo->head_cache, "\tQuery: `%s`\n", m_query_txt); } 3. How Master writes Annotate_rows events to the binary log ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The event is written to the binary log just before the group of Table_map events which precede corresponding Rows events (one query may generate several Table map events in the binary log, but the corresponding Annotate_rows event must be written only once before the first Table map event; hence the boolean variable 'with_annotate' below): int write_locked_table_maps(THD *thd) { ... bool with_annotate= thd->variables.binlog_annotate_rows_events; ... for (uint i= 0; i < ... <number of tables> ...; ++i) { ... thd->binlog_write_table_map(table, ..., with_annotate); with_annotate= 0; // write Annotate_event not more than once ... } ... } int THD::binlog_write_table_map(TABLE *table, ..., bool with_annotate) { ... Table_map_log_event the_event(...); ... if (with_annotate) { Annotate_rows_log_event anno(this); mysql_bin_log.write(&anno); } mysql_bin_log.write(&the_event); ... } 4. How slave treats replicate-annotate-rows-events option ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The replicate-annotate-rows-events option is treated just as the session value of the binlog_annotate_rows_events variable for the slave IO and SQL threads. This setting is done during initialization of these threads: pthread_handler_t handle_slave_io(void *arg) { THD *thd= new THD; ... init_slave_thread(thd, SLAVE_THD_IO); ... } pthread_handler_t handle_slave_sql(void *arg) { THD *thd= new THD; ... init_slave_thread(thd, SLAVE_THD_SQL); ... } int init_slave_thread(THD* thd, SLAVE_THD_TYPE thd_type) { ... thd->variables.binlog_annotate_rows_events= opt_replicate_annotate_rows_events; ... } 5. How slave IO thread requests Annotate_rows events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If the replicate-annotate-rows-events option is not set on a slave, there is no need for master to send Annotate_rows events to this slave. The slave (or mysqlbinlog in remote case), before requesting binlog dump via the COM_BINLOG_DUMP command, informs the master whether it should send these events by executing the newly added COM_BINLOG_DUMP_OPTIONS_EXT server command: case COM_BINLOG_DUMP_OPTIONS_EXT: thd->binlog_dump_flags_ext= packet[0]; my_ok(thd); break; Note. We add this new command and don't use COM_BINLOG_DUMP to avoid possible conflicts with MySQL/Sun. 6. How master executes the request ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ case COM_BINLOG_DUMP: { ... flags= uint2korr(packet + 4); ... mysql_binlog_send(thd, ..., flags); ... } void mysql_binlog_send(THD* thd, ..., ushort flags) { ... Log_event::read_log_event(&log, packet, ...); ... if ((*packet)[EVENT_TYPE_OFFSET + 1] != ANNOTATE_ROWS_EVENT || flags & BINLOG_SEND_ANNOTATE_ROWS_EVENT) { my_net_write(net, packet->ptr(), packet->length()); } ... } 7. How slave SQL thread processes Annotate_rows events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The slave processes each recieved event by "applying" it, i.e. by calling the Log_event::apply_event() function which in turn calls the virtual do_apply_event() member specific for each type of the event. int exec_relay_log_event(THD* thd, Relay_log_info* rli) { ... Log_event *ev = next_event(rli); ... apply_event_and_update_pos(ev, ...); if (ev->get_type_code() != FORMAT_DESCRIPTION_EVENT) delete ev; ... } int apply_event_and_update_pos(Log_event *ev, ...) { ... ev->apply_event(...); ... } int Log_event::apply_event(...) { return do_apply_event(...); } What does it mean to "apply" an Annotate_rows event? It means to set current thd query to that of the described by the event, i.e. to the query which caused the subsequent Rows events (see "How Master writes Annotate_rows events to the binary log" to follow what happens further when the subsequent Rows events are applied): int Annotate_rows_log_event::do_apply_event(...) { thd->set_query(m_query_txt, m_query_len); } NOTE. I am not sure, but possibly current values of thd->query and thd->query_length should be saved before calling set_query() and to be restored on the Annotate_rows_log_event object deletion. Is it really needed ? After calling this do_apply_event() function we may not delete the Annotate_rows_log_event object immediatedly (see exec_relay_log_event() above) because thd->query now points to the string inside this object. We may keep the pointer to this object in the Relay_log_info: class Relay_log_info { public: ... void set_annotate_event(Annotate_rows_log_event*); Annotate_rows_log_event* get_annotate_event(); void free_annotate_event(); ... private: Annotate_rows_log_event* m_annotate_event; }; The saved Annotate_rows object should be deleted when all corresponding Rows events will be processed: int exec_relay_log_event(THD* thd, Relay_log_info* rli) { ... Log_event *ev= next_event(rli); ... apply_event_and_update_pos(ev, ...); if (rli->get_annotate_event() && is_last_rows_event(ev)) rli->free_annotate_event(); else if (ev->get_type_code() == ANNOTATE_ROWS_EVENT) rli->set_annotate_event((Annotate_rows_log_event*) ev); else if (ev->get_type_code() != FORMAT_DESCRIPTION_EVENT) delete ev; ... } where bool is_last_rows_event(Log_event* ev) { Log_event_type type= ev->get_type_code(); if (IS_ROWS_EVENT_TYPE(type)) { Rows_log_event* rows= (Rows_log_event*)ev; return rows->get_flags(Rows_log_event::STMT_END_F); } return 0; } #define IS_ROWS_EVENT_TYPE(type) ((type) == WRITE_ROWS_EVENT || \ (type) == UPDATE_ROWS_EVENT || \ (type) == DELETE_ROWS_EVENT) 8. General remarks ~~~~~~~~~~~~~~~~~~ Kristian noticed that introducing new log event type should be coordinated somehow with MySQL/Sun: Kristian: The numeric code for this event must be assigned carefully. It should be coordinated with MySQL/Sun, otherwise we can get into a situation where MySQL uses the same numeric code for one event that MariaDB uses for ANNOTATE_ROWS_EVENT, which would make merging the two impossible. Alex: I reserved about 20 numbers not to have possible conflicts with MySQL. Kristian: Still, I think it would be appropriate to send a polite email to internals(a)lists.mysql.com about this and suggesting to reserve the event number. ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

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[Maria-developers] Progress (by Knielsen): Store in binlog text of statements that caused RBR events (47)
by worklog-noreply＠askmonty.org 25 May '10

25 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Store in binlog text of statements that caused RBR events CREATION DATE..: Sat, 15 Aug 2009, 23:48 SUPERVISOR.....: Monty IMPLEMENTOR....: COPIES TO......: Knielsen, Serg CATEGORY.......: Server-Sprint TASK ID........: 47 (http://askmonty.org/worklog/?tid=47) VERSION........: Server-9.x STATUS.........: Code-Review PRIORITY.......: 60 WORKED HOURS...: 31 ESTIMATE.......: 4 (hours remain) ORIG. ESTIMATE.: 35 PROGRESS NOTES: -=-=(Knielsen - Tue, 25 May 2010, 08:29)=-=- Help debug strange problem in mysqlbinlog.test. Worked 1 hour and estimate 4 hours remain (original estimate unchanged). -=-=(Knielsen - Mon, 17 May 2010, 08:45)=-=- Merge with latest trunk and run Buildbot tests. Worked 1 hour and estimate 5 hours remain (original estimate unchanged). -=-=(Knielsen - Wed, 05 May 2010, 13:53)=-=- Review of fixes to first review done. No new issues found. Worked 2 hours and estimate 6 hours remain (original estimate unchanged). -=-=(Knielsen - Fri, 23 Apr 2010, 12:51)=-=- Status updated. --- /tmp/wklog.47.old.28747 2010-04-23 12:51:36.000000000 +0000 +++ /tmp/wklog.47.new.28747 2010-04-23 12:51:36.000000000 +0000 @@ -1 +1 @@ -In-Progress +Code-Review -=-=(Knielsen - Tue, 06 Apr 2010, 15:26)=-=- Code review (mailed to maria-developers@). Worked 7 hours and estimate 8 hours remain (original estimate unchanged). -=-=(Knielsen - Tue, 06 Apr 2010, 15:25)=-=- Status updated. --- /tmp/wklog.47.old.12734 2010-04-06 15:25:54.000000000 +0000 +++ /tmp/wklog.47.new.12734 2010-04-06 15:25:54.000000000 +0000 @@ -1 +1 @@ -Code-Review +In-Progress -=-=(Knielsen - Mon, 29 Mar 2010, 10:59)=-=- Status updated. --- /tmp/wklog.47.old.27790 2010-03-29 10:59:53.000000000 +0000 +++ /tmp/wklog.47.new.27790 2010-03-29 10:59:53.000000000 +0000 @@ -1 +1 @@ -In-Progress +Code-Review -=-=(Alexi - Thu, 18 Feb 2010, 19:29)=-=- Worked 20 hours (alexi) Worked 20 hours and estimate 15 hours remain (original estimate unchanged). -=-=(Serg - Fri, 05 Feb 2010, 14:04)=-=- Observers changed: Knielsen,Serg -=-=(Guest - Fri, 05 Feb 2010, 13:40)=-=- Category updated. --- /tmp/wklog.47.old.9197 2010-02-05 13:40:36.000000000 +0200 +++ /tmp/wklog.47.new.9197 2010-02-05 13:40:36.000000000 +0200 @@ -1 +1 @@ -Server-RawIdeaBin +Server-Sprint ------------------------------------------------------------ -=-=(View All Progress Notes, 31 total)=-=- http://askmonty.org/worklog/index.pl?tid=47&nolimit=1 DESCRIPTION: Store in binlog (and show in mysqlbinlog output) texts of statements that caused RBR events This is needed for (list from Monty): - Easier to understand why updates happened - Would make it easier to find out where in application things went wrong (as you can search for exact strings) - Allow one to filter things based on comments in the statement. The cost of this can be that the binlog will be approximately 2x in size (especially insert of big blob's would be a bit painful), so this should be an optional feature. HIGH-LEVEL SPECIFICATION: Content ~~~~~~~ 1. Annotate_rows_log_event 2. Server option: --binlog-annotate-rows-events 3. Server option: --replicate-annotate-rows-events 4. mysqlbinlog option: --print-annotate-rows-events 5. mysqlbinlog output 1. Annotate_rows_log_event [ ANNOTATE_ROWS_EVENT ] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Describes the query which caused the corresponding rows events. Has empty post-header and contains the query text in its data part. Example: ************************ ANNOTATE_ROWS_EVENT ************************ 00000220 | B6 A0 2C 4B | time_when = 1261215926 00000224 | 33 | event_type = 51 00000225 | 64 00 00 00 | server_id = 100 00000229 | 36 00 00 00 | event_len = 54 0000022D | 56 02 00 00 | log_pos = 00000256 00000231 | 00 00 | flags = <none> ------------------------ 00000233 | 49 4E 53 45 | query = "INSERT INTO t1 VALUES (1), (2), (3)" 00000237 | 52 54 20 49 | 0000023B | 4E 54 4F 20 | 0000023F | 74 31 20 56 | 00000243 | 41 4C 55 45 | 00000247 | 53 20 28 31 | 0000024B | 29 2C 20 28 | 0000024F | 32 29 2C 20 | 00000253 | 28 33 29 | ************************ In binary log, Annotate_rows event follows the (possible) 'BEGIN' Query event and precedes the first of Table map events which accompany the corresponding rows events. (See example in the "mysqlbinlog output" section below.) 2. Server option: --binlog-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tells the master to write Annotate_rows events to the binary log. * Variable Name: binlog_annotate_rows_events * Scope: Global & Session * Access Type: Dynamic * Data Type: bool * Default Value: OFF NOTE. Session values allows to annotate only some selected statements: ... SET SESSION binlog_annotate_rows_events=ON; ... statements to be annotated ... SET SESSION binlog_annotate_rows_events=OFF; ... statements not to be annotated ... 3. Server option: --replicate-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tells the slave to reproduce Annotate_rows events recieved from the master in its own binary log (sensible only in pair with log-slave-updates option). * Variable Name: replicate_annotate_rows_events * Scope: Global * Access Type: Read only * Data Type: bool * Default Value: OFF NOTE. Why do we additionally need this 'replicate' option? Why not to make the slave to reproduce this events when its binlog-annotate-rows-events global value is ON? Well, because, for example, we may want to configure the slave which should reproduce Annotate_rows events but has global binlog-annotate-rows-events = OFF meaning this to be the default value for the client threads (see also "How slave treats replicate-annotate-rows-events option" in LLD part). 4. mysqlbinlog option: --print-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ With this option, mysqlbinlog prints the content of Annotate_rows events (if the binary log does contain them). Without this option (i.e. by default), mysqlbinlog skips Annotate_rows events. 5. mysqlbinlog output ~~~~~~~~~~~~~~~~~~~~~ With --print-annotate-rows-events, mysqlbinlog outputs Annotate_rows events in a form like this: ... # at 1646 #091219 12:45:26 server id 100 end_log_pos 1714 Query thread_id=1 exec_time=0 error_code=0 SET TIMESTAMP=1261215926/*!*/; BEGIN /*!*/; # at 1714 # at 1812 # at 1853 # at 1894 # at 1938 #091219 12:45:26 server id 100 end_log_pos 1812 Query: `DELETE t1, t2 FROM t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.a=t2.a AND t2.a=t3.a` #091219 12:45:26 server id 100 end_log_pos 1853 Table_map: `test`.`t1` mapped to number 16 #091219 12:45:26 server id 100 end_log_pos 1894 Table_map: `test`.`t2` mapped to number 17 #091219 12:45:26 server id 100 end_log_pos 1938 Delete_rows: table id 16 #091219 12:45:26 server id 100 end_log_pos 1982 Delete_rows: table id 17 flags: STMT_END_F ... LOW-LEVEL DESIGN: Content ~~~~~~~ 1. Annotate_rows event number 2. Outline of Annotate_rows event behavior 3. How Master writes Annotate_rows events to the binary log 4. How slave treats replicate-annotate-rows-events option 5. How slave IO thread requests Annotate_rows events 6. How master executes the request 7. How slave SQL thread processes Annotate_rows events 8. General remarks 1. Annotate_rows event number ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To avoid possible event numbers conflict with MySQL/Sun, we leave a gap between the last MySQL event number and the Annotate_rows event number: enum Log_event_type { ... INCIDENT_EVENT= 26, // New MySQL event numbers are to be added here MYSQL_EVENTS_END, MARIA_EVENTS_BEGIN= 51, // New Maria event numbers start from here ANNOTATE_ROWS_EVENT= 51, ENUM_END_EVENT }; together with the corresponding extension of 'post_header_len' array in the Format description event. (This extension does not affect the compatibility of the binary log). Here is how Format description event looks like with this extension: ************************ FORMAT_DESCRIPTION_EVENT ************************ 00000004 | A1 A0 2C 4B | time_when = 1261215905 00000008 | 0F | event_type = 15 00000009 | 64 00 00 00 | server_id = 100 0000000D | 7F 00 00 00 | event_len = 127 00000011 | 83 00 00 00 | log_pos = 00000083 00000015 | 01 00 | flags = LOG_EVENT_BINLOG_IN_USE_F ------------------------ 00000017 | 04 00 | binlog_ver = 4 00000019 | 35 2E 32 2E | server_ver = 5.2.0-MariaDB-alpha-debug-log ..... ... 0000004B | A1 A0 2C 4B | time_created = 1261215905 0000004F | 13 | common_header_len = 19 ------------------------ post_header_len ------------------------ 00000050 | 38 | 56 - START_EVENT_V3 [1] ..... ... 00000069 | 02 | 2 - INCIDENT_EVENT [26] 0000006A | 00 | 0 - RESERVED [27] ..... ... 00000081 | 00 | 0 - RESERVED [50] 00000082 | 00 | 0 - ANNOTATE_ROWS_EVENT [51] ************************ 2. Outline of Annotate_rows event behavior ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Each Annotate_rows_log_event object has two private members describing the corresponding query: char *m_query_txt; uint m_query_len; When the object is created for writing to a binary log, this query is taken from 'thd' (for short, below we omit the 'Annotate_rows_log_event::' prefix as well as other implementation details): Annotate_rows_log_event(THD *thd) { m_query_txt = thd->query(); m_query_len = thd->query_length(); } When the object is read from a binary log, the query is taken from the buffer containing the binary log representation of the event (this buffer is allocated in Log_event object from which all Log events are derived): Annotate_rows_log_event(char *buf, uint event_len, Format_description_log_event *desc) { m_query_len = event_len - desc->common_header_len; m_query_txt = buf + desc->common_header_len; } The events are written to the binary log by the Log_event::write() member which calls virtual write_data_header() and write_data_body() members ("data header" and "post header" are synonym in replication terminology). In our case, data header is empty and data body is just the query: bool write_data_body(IO_CACHE *file) { return my_b_safe_write(file, (uchar*) m_query_txt, m_query_len); } Printing the event is just printing the query: void Annotate_rows_log_event::print(FILE *file, PRINT_EVENT_INFO *pinfo) { my_b_printf(&pinfo->head_cache, "\tQuery: `%s`\n", m_query_txt); } 3. How Master writes Annotate_rows events to the binary log ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The event is written to the binary log just before the group of Table_map events which precede corresponding Rows events (one query may generate several Table map events in the binary log, but the corresponding Annotate_rows event must be written only once before the first Table map event; hence the boolean variable 'with_annotate' below): int write_locked_table_maps(THD *thd) { ... bool with_annotate= thd->variables.binlog_annotate_rows_events; ... for (uint i= 0; i < ... <number of tables> ...; ++i) { ... thd->binlog_write_table_map(table, ..., with_annotate); with_annotate= 0; // write Annotate_event not more than once ... } ... } int THD::binlog_write_table_map(TABLE *table, ..., bool with_annotate) { ... Table_map_log_event the_event(...); ... if (with_annotate) { Annotate_rows_log_event anno(this); mysql_bin_log.write(&anno); } mysql_bin_log.write(&the_event); ... } 4. How slave treats replicate-annotate-rows-events option ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The replicate-annotate-rows-events option is treated just as the session value of the binlog_annotate_rows_events variable for the slave IO and SQL threads. This setting is done during initialization of these threads: pthread_handler_t handle_slave_io(void *arg) { THD *thd= new THD; ... init_slave_thread(thd, SLAVE_THD_IO); ... } pthread_handler_t handle_slave_sql(void *arg) { THD *thd= new THD; ... init_slave_thread(thd, SLAVE_THD_SQL); ... } int init_slave_thread(THD* thd, SLAVE_THD_TYPE thd_type) { ... thd->variables.binlog_annotate_rows_events= opt_replicate_annotate_rows_events; ... } 5. How slave IO thread requests Annotate_rows events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If the replicate-annotate-rows-events option is not set on a slave, there is no need for master to send Annotate_rows events to this slave. The slave (or mysqlbinlog in remote case), before requesting binlog dump via the COM_BINLOG_DUMP command, informs the master whether it should send these events by executing the newly added COM_BINLOG_DUMP_OPTIONS_EXT server command: case COM_BINLOG_DUMP_OPTIONS_EXT: thd->binlog_dump_flags_ext= packet[0]; my_ok(thd); break; Note. We add this new command and don't use COM_BINLOG_DUMP to avoid possible conflicts with MySQL/Sun. 6. How master executes the request ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ case COM_BINLOG_DUMP: { ... flags= uint2korr(packet + 4); ... mysql_binlog_send(thd, ..., flags); ... } void mysql_binlog_send(THD* thd, ..., ushort flags) { ... Log_event::read_log_event(&log, packet, ...); ... if ((*packet)[EVENT_TYPE_OFFSET + 1] != ANNOTATE_ROWS_EVENT || flags & BINLOG_SEND_ANNOTATE_ROWS_EVENT) { my_net_write(net, packet->ptr(), packet->length()); } ... } 7. How slave SQL thread processes Annotate_rows events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The slave processes each recieved event by "applying" it, i.e. by calling the Log_event::apply_event() function which in turn calls the virtual do_apply_event() member specific for each type of the event. int exec_relay_log_event(THD* thd, Relay_log_info* rli) { ... Log_event *ev = next_event(rli); ... apply_event_and_update_pos(ev, ...); if (ev->get_type_code() != FORMAT_DESCRIPTION_EVENT) delete ev; ... } int apply_event_and_update_pos(Log_event *ev, ...) { ... ev->apply_event(...); ... } int Log_event::apply_event(...) { return do_apply_event(...); } What does it mean to "apply" an Annotate_rows event? It means to set current thd query to that of the described by the event, i.e. to the query which caused the subsequent Rows events (see "How Master writes Annotate_rows events to the binary log" to follow what happens further when the subsequent Rows events are applied): int Annotate_rows_log_event::do_apply_event(...) { thd->set_query(m_query_txt, m_query_len); } NOTE. I am not sure, but possibly current values of thd->query and thd->query_length should be saved before calling set_query() and to be restored on the Annotate_rows_log_event object deletion. Is it really needed ? After calling this do_apply_event() function we may not delete the Annotate_rows_log_event object immediatedly (see exec_relay_log_event() above) because thd->query now points to the string inside this object. We may keep the pointer to this object in the Relay_log_info: class Relay_log_info { public: ... void set_annotate_event(Annotate_rows_log_event*); Annotate_rows_log_event* get_annotate_event(); void free_annotate_event(); ... private: Annotate_rows_log_event* m_annotate_event; }; The saved Annotate_rows object should be deleted when all corresponding Rows events will be processed: int exec_relay_log_event(THD* thd, Relay_log_info* rli) { ... Log_event *ev= next_event(rli); ... apply_event_and_update_pos(ev, ...); if (rli->get_annotate_event() && is_last_rows_event(ev)) rli->free_annotate_event(); else if (ev->get_type_code() == ANNOTATE_ROWS_EVENT) rli->set_annotate_event((Annotate_rows_log_event*) ev); else if (ev->get_type_code() != FORMAT_DESCRIPTION_EVENT) delete ev; ... } where bool is_last_rows_event(Log_event* ev) { Log_event_type type= ev->get_type_code(); if (IS_ROWS_EVENT_TYPE(type)) { Rows_log_event* rows= (Rows_log_event*)ev; return rows->get_flags(Rows_log_event::STMT_END_F); } return 0; } #define IS_ROWS_EVENT_TYPE(type) ((type) == WRITE_ROWS_EVENT || \ (type) == UPDATE_ROWS_EVENT || \ (type) == DELETE_ROWS_EVENT) 8. General remarks ~~~~~~~~~~~~~~~~~~ Kristian noticed that introducing new log event type should be coordinated somehow with MySQL/Sun: Kristian: The numeric code for this event must be assigned carefully. It should be coordinated with MySQL/Sun, otherwise we can get into a situation where MySQL uses the same numeric code for one event that MariaDB uses for ANNOTATE_ROWS_EVENT, which would make merging the two impossible. Alex: I reserved about 20 numbers not to have possible conflicts with MySQL. Kristian: Still, I think it would be appropriate to send a polite email to internals(a)lists.mysql.com about this and suggesting to reserve the event number. ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

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[Maria-developers] Progress (by Knielsen): Store in binlog text of statements that caused RBR events (47)
by worklog-noreply＠askmonty.org 25 May '10

25 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Store in binlog text of statements that caused RBR events CREATION DATE..: Sat, 15 Aug 2009, 23:48 SUPERVISOR.....: Monty IMPLEMENTOR....: COPIES TO......: Knielsen, Serg CATEGORY.......: Server-Sprint TASK ID........: 47 (http://askmonty.org/worklog/?tid=47) VERSION........: Server-9.x STATUS.........: Code-Review PRIORITY.......: 60 WORKED HOURS...: 31 ESTIMATE.......: 4 (hours remain) ORIG. ESTIMATE.: 35 PROGRESS NOTES: -=-=(Knielsen - Tue, 25 May 2010, 08:29)=-=- Help debug strange problem in mysqlbinlog.test. Worked 1 hour and estimate 4 hours remain (original estimate unchanged). -=-=(Knielsen - Mon, 17 May 2010, 08:45)=-=- Merge with latest trunk and run Buildbot tests. Worked 1 hour and estimate 5 hours remain (original estimate unchanged). -=-=(Knielsen - Wed, 05 May 2010, 13:53)=-=- Review of fixes to first review done. No new issues found. Worked 2 hours and estimate 6 hours remain (original estimate unchanged). -=-=(Knielsen - Fri, 23 Apr 2010, 12:51)=-=- Status updated. --- /tmp/wklog.47.old.28747 2010-04-23 12:51:36.000000000 +0000 +++ /tmp/wklog.47.new.28747 2010-04-23 12:51:36.000000000 +0000 @@ -1 +1 @@ -In-Progress +Code-Review -=-=(Knielsen - Tue, 06 Apr 2010, 15:26)=-=- Code review (mailed to maria-developers@). Worked 7 hours and estimate 8 hours remain (original estimate unchanged). -=-=(Knielsen - Tue, 06 Apr 2010, 15:25)=-=- Status updated. --- /tmp/wklog.47.old.12734 2010-04-06 15:25:54.000000000 +0000 +++ /tmp/wklog.47.new.12734 2010-04-06 15:25:54.000000000 +0000 @@ -1 +1 @@ -Code-Review +In-Progress -=-=(Knielsen - Mon, 29 Mar 2010, 10:59)=-=- Status updated. --- /tmp/wklog.47.old.27790 2010-03-29 10:59:53.000000000 +0000 +++ /tmp/wklog.47.new.27790 2010-03-29 10:59:53.000000000 +0000 @@ -1 +1 @@ -In-Progress +Code-Review -=-=(Alexi - Thu, 18 Feb 2010, 19:29)=-=- Worked 20 hours (alexi) Worked 20 hours and estimate 15 hours remain (original estimate unchanged). -=-=(Serg - Fri, 05 Feb 2010, 14:04)=-=- Observers changed: Knielsen,Serg -=-=(Guest - Fri, 05 Feb 2010, 13:40)=-=- Category updated. --- /tmp/wklog.47.old.9197 2010-02-05 13:40:36.000000000 +0200 +++ /tmp/wklog.47.new.9197 2010-02-05 13:40:36.000000000 +0200 @@ -1 +1 @@ -Server-RawIdeaBin +Server-Sprint ------------------------------------------------------------ -=-=(View All Progress Notes, 31 total)=-=- http://askmonty.org/worklog/index.pl?tid=47&nolimit=1 DESCRIPTION: Store in binlog (and show in mysqlbinlog output) texts of statements that caused RBR events This is needed for (list from Monty): - Easier to understand why updates happened - Would make it easier to find out where in application things went wrong (as you can search for exact strings) - Allow one to filter things based on comments in the statement. The cost of this can be that the binlog will be approximately 2x in size (especially insert of big blob's would be a bit painful), so this should be an optional feature. HIGH-LEVEL SPECIFICATION: Content ~~~~~~~ 1. Annotate_rows_log_event 2. Server option: --binlog-annotate-rows-events 3. Server option: --replicate-annotate-rows-events 4. mysqlbinlog option: --print-annotate-rows-events 5. mysqlbinlog output 1. Annotate_rows_log_event [ ANNOTATE_ROWS_EVENT ] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Describes the query which caused the corresponding rows events. Has empty post-header and contains the query text in its data part. Example: ************************ ANNOTATE_ROWS_EVENT ************************ 00000220 | B6 A0 2C 4B | time_when = 1261215926 00000224 | 33 | event_type = 51 00000225 | 64 00 00 00 | server_id = 100 00000229 | 36 00 00 00 | event_len = 54 0000022D | 56 02 00 00 | log_pos = 00000256 00000231 | 00 00 | flags = <none> ------------------------ 00000233 | 49 4E 53 45 | query = "INSERT INTO t1 VALUES (1), (2), (3)" 00000237 | 52 54 20 49 | 0000023B | 4E 54 4F 20 | 0000023F | 74 31 20 56 | 00000243 | 41 4C 55 45 | 00000247 | 53 20 28 31 | 0000024B | 29 2C 20 28 | 0000024F | 32 29 2C 20 | 00000253 | 28 33 29 | ************************ In binary log, Annotate_rows event follows the (possible) 'BEGIN' Query event and precedes the first of Table map events which accompany the corresponding rows events. (See example in the "mysqlbinlog output" section below.) 2. Server option: --binlog-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tells the master to write Annotate_rows events to the binary log. * Variable Name: binlog_annotate_rows_events * Scope: Global & Session * Access Type: Dynamic * Data Type: bool * Default Value: OFF NOTE. Session values allows to annotate only some selected statements: ... SET SESSION binlog_annotate_rows_events=ON; ... statements to be annotated ... SET SESSION binlog_annotate_rows_events=OFF; ... statements not to be annotated ... 3. Server option: --replicate-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tells the slave to reproduce Annotate_rows events recieved from the master in its own binary log (sensible only in pair with log-slave-updates option). * Variable Name: replicate_annotate_rows_events * Scope: Global * Access Type: Read only * Data Type: bool * Default Value: OFF NOTE. Why do we additionally need this 'replicate' option? Why not to make the slave to reproduce this events when its binlog-annotate-rows-events global value is ON? Well, because, for example, we may want to configure the slave which should reproduce Annotate_rows events but has global binlog-annotate-rows-events = OFF meaning this to be the default value for the client threads (see also "How slave treats replicate-annotate-rows-events option" in LLD part). 4. mysqlbinlog option: --print-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ With this option, mysqlbinlog prints the content of Annotate_rows events (if the binary log does contain them). Without this option (i.e. by default), mysqlbinlog skips Annotate_rows events. 5. mysqlbinlog output ~~~~~~~~~~~~~~~~~~~~~ With --print-annotate-rows-events, mysqlbinlog outputs Annotate_rows events in a form like this: ... # at 1646 #091219 12:45:26 server id 100 end_log_pos 1714 Query thread_id=1 exec_time=0 error_code=0 SET TIMESTAMP=1261215926/*!*/; BEGIN /*!*/; # at 1714 # at 1812 # at 1853 # at 1894 # at 1938 #091219 12:45:26 server id 100 end_log_pos 1812 Query: `DELETE t1, t2 FROM t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.a=t2.a AND t2.a=t3.a` #091219 12:45:26 server id 100 end_log_pos 1853 Table_map: `test`.`t1` mapped to number 16 #091219 12:45:26 server id 100 end_log_pos 1894 Table_map: `test`.`t2` mapped to number 17 #091219 12:45:26 server id 100 end_log_pos 1938 Delete_rows: table id 16 #091219 12:45:26 server id 100 end_log_pos 1982 Delete_rows: table id 17 flags: STMT_END_F ... LOW-LEVEL DESIGN: Content ~~~~~~~ 1. Annotate_rows event number 2. Outline of Annotate_rows event behavior 3. How Master writes Annotate_rows events to the binary log 4. How slave treats replicate-annotate-rows-events option 5. How slave IO thread requests Annotate_rows events 6. How master executes the request 7. How slave SQL thread processes Annotate_rows events 8. General remarks 1. Annotate_rows event number ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To avoid possible event numbers conflict with MySQL/Sun, we leave a gap between the last MySQL event number and the Annotate_rows event number: enum Log_event_type { ... INCIDENT_EVENT= 26, // New MySQL event numbers are to be added here MYSQL_EVENTS_END, MARIA_EVENTS_BEGIN= 51, // New Maria event numbers start from here ANNOTATE_ROWS_EVENT= 51, ENUM_END_EVENT }; together with the corresponding extension of 'post_header_len' array in the Format description event. (This extension does not affect the compatibility of the binary log). Here is how Format description event looks like with this extension: ************************ FORMAT_DESCRIPTION_EVENT ************************ 00000004 | A1 A0 2C 4B | time_when = 1261215905 00000008 | 0F | event_type = 15 00000009 | 64 00 00 00 | server_id = 100 0000000D | 7F 00 00 00 | event_len = 127 00000011 | 83 00 00 00 | log_pos = 00000083 00000015 | 01 00 | flags = LOG_EVENT_BINLOG_IN_USE_F ------------------------ 00000017 | 04 00 | binlog_ver = 4 00000019 | 35 2E 32 2E | server_ver = 5.2.0-MariaDB-alpha-debug-log ..... ... 0000004B | A1 A0 2C 4B | time_created = 1261215905 0000004F | 13 | common_header_len = 19 ------------------------ post_header_len ------------------------ 00000050 | 38 | 56 - START_EVENT_V3 [1] ..... ... 00000069 | 02 | 2 - INCIDENT_EVENT [26] 0000006A | 00 | 0 - RESERVED [27] ..... ... 00000081 | 00 | 0 - RESERVED [50] 00000082 | 00 | 0 - ANNOTATE_ROWS_EVENT [51] ************************ 2. Outline of Annotate_rows event behavior ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Each Annotate_rows_log_event object has two private members describing the corresponding query: char *m_query_txt; uint m_query_len; When the object is created for writing to a binary log, this query is taken from 'thd' (for short, below we omit the 'Annotate_rows_log_event::' prefix as well as other implementation details): Annotate_rows_log_event(THD *thd) { m_query_txt = thd->query(); m_query_len = thd->query_length(); } When the object is read from a binary log, the query is taken from the buffer containing the binary log representation of the event (this buffer is allocated in Log_event object from which all Log events are derived): Annotate_rows_log_event(char *buf, uint event_len, Format_description_log_event *desc) { m_query_len = event_len - desc->common_header_len; m_query_txt = buf + desc->common_header_len; } The events are written to the binary log by the Log_event::write() member which calls virtual write_data_header() and write_data_body() members ("data header" and "post header" are synonym in replication terminology). In our case, data header is empty and data body is just the query: bool write_data_body(IO_CACHE *file) { return my_b_safe_write(file, (uchar*) m_query_txt, m_query_len); } Printing the event is just printing the query: void Annotate_rows_log_event::print(FILE *file, PRINT_EVENT_INFO *pinfo) { my_b_printf(&pinfo->head_cache, "\tQuery: `%s`\n", m_query_txt); } 3. How Master writes Annotate_rows events to the binary log ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The event is written to the binary log just before the group of Table_map events which precede corresponding Rows events (one query may generate several Table map events in the binary log, but the corresponding Annotate_rows event must be written only once before the first Table map event; hence the boolean variable 'with_annotate' below): int write_locked_table_maps(THD *thd) { ... bool with_annotate= thd->variables.binlog_annotate_rows_events; ... for (uint i= 0; i < ... <number of tables> ...; ++i) { ... thd->binlog_write_table_map(table, ..., with_annotate); with_annotate= 0; // write Annotate_event not more than once ... } ... } int THD::binlog_write_table_map(TABLE *table, ..., bool with_annotate) { ... Table_map_log_event the_event(...); ... if (with_annotate) { Annotate_rows_log_event anno(this); mysql_bin_log.write(&anno); } mysql_bin_log.write(&the_event); ... } 4. How slave treats replicate-annotate-rows-events option ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The replicate-annotate-rows-events option is treated just as the session value of the binlog_annotate_rows_events variable for the slave IO and SQL threads. This setting is done during initialization of these threads: pthread_handler_t handle_slave_io(void *arg) { THD *thd= new THD; ... init_slave_thread(thd, SLAVE_THD_IO); ... } pthread_handler_t handle_slave_sql(void *arg) { THD *thd= new THD; ... init_slave_thread(thd, SLAVE_THD_SQL); ... } int init_slave_thread(THD* thd, SLAVE_THD_TYPE thd_type) { ... thd->variables.binlog_annotate_rows_events= opt_replicate_annotate_rows_events; ... } 5. How slave IO thread requests Annotate_rows events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If the replicate-annotate-rows-events option is not set on a slave, there is no need for master to send Annotate_rows events to this slave. The slave (or mysqlbinlog in remote case), before requesting binlog dump via the COM_BINLOG_DUMP command, informs the master whether it should send these events by executing the newly added COM_BINLOG_DUMP_OPTIONS_EXT server command: case COM_BINLOG_DUMP_OPTIONS_EXT: thd->binlog_dump_flags_ext= packet[0]; my_ok(thd); break; Note. We add this new command and don't use COM_BINLOG_DUMP to avoid possible conflicts with MySQL/Sun. 6. How master executes the request ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ case COM_BINLOG_DUMP: { ... flags= uint2korr(packet + 4); ... mysql_binlog_send(thd, ..., flags); ... } void mysql_binlog_send(THD* thd, ..., ushort flags) { ... Log_event::read_log_event(&log, packet, ...); ... if ((*packet)[EVENT_TYPE_OFFSET + 1] != ANNOTATE_ROWS_EVENT || flags & BINLOG_SEND_ANNOTATE_ROWS_EVENT) { my_net_write(net, packet->ptr(), packet->length()); } ... } 7. How slave SQL thread processes Annotate_rows events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The slave processes each recieved event by "applying" it, i.e. by calling the Log_event::apply_event() function which in turn calls the virtual do_apply_event() member specific for each type of the event. int exec_relay_log_event(THD* thd, Relay_log_info* rli) { ... Log_event *ev = next_event(rli); ... apply_event_and_update_pos(ev, ...); if (ev->get_type_code() != FORMAT_DESCRIPTION_EVENT) delete ev; ... } int apply_event_and_update_pos(Log_event *ev, ...) { ... ev->apply_event(...); ... } int Log_event::apply_event(...) { return do_apply_event(...); } What does it mean to "apply" an Annotate_rows event? It means to set current thd query to that of the described by the event, i.e. to the query which caused the subsequent Rows events (see "How Master writes Annotate_rows events to the binary log" to follow what happens further when the subsequent Rows events are applied): int Annotate_rows_log_event::do_apply_event(...) { thd->set_query(m_query_txt, m_query_len); } NOTE. I am not sure, but possibly current values of thd->query and thd->query_length should be saved before calling set_query() and to be restored on the Annotate_rows_log_event object deletion. Is it really needed ? After calling this do_apply_event() function we may not delete the Annotate_rows_log_event object immediatedly (see exec_relay_log_event() above) because thd->query now points to the string inside this object. We may keep the pointer to this object in the Relay_log_info: class Relay_log_info { public: ... void set_annotate_event(Annotate_rows_log_event*); Annotate_rows_log_event* get_annotate_event(); void free_annotate_event(); ... private: Annotate_rows_log_event* m_annotate_event; }; The saved Annotate_rows object should be deleted when all corresponding Rows events will be processed: int exec_relay_log_event(THD* thd, Relay_log_info* rli) { ... Log_event *ev= next_event(rli); ... apply_event_and_update_pos(ev, ...); if (rli->get_annotate_event() && is_last_rows_event(ev)) rli->free_annotate_event(); else if (ev->get_type_code() == ANNOTATE_ROWS_EVENT) rli->set_annotate_event((Annotate_rows_log_event*) ev); else if (ev->get_type_code() != FORMAT_DESCRIPTION_EVENT) delete ev; ... } where bool is_last_rows_event(Log_event* ev) { Log_event_type type= ev->get_type_code(); if (IS_ROWS_EVENT_TYPE(type)) { Rows_log_event* rows= (Rows_log_event*)ev; return rows->get_flags(Rows_log_event::STMT_END_F); } return 0; } #define IS_ROWS_EVENT_TYPE(type) ((type) == WRITE_ROWS_EVENT || \ (type) == UPDATE_ROWS_EVENT || \ (type) == DELETE_ROWS_EVENT) 8. General remarks ~~~~~~~~~~~~~~~~~~ Kristian noticed that introducing new log event type should be coordinated somehow with MySQL/Sun: Kristian: The numeric code for this event must be assigned carefully. It should be coordinated with MySQL/Sun, otherwise we can get into a situation where MySQL uses the same numeric code for one event that MariaDB uses for ANNOTATE_ROWS_EVENT, which would make merging the two impossible. Alex: I reserved about 20 numbers not to have possible conflicts with MySQL. Kristian: Still, I think it would be appropriate to send a polite email to internals(a)lists.mysql.com about this and suggesting to reserve the event number. ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

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[Maria-developers] Progress (by Knielsen): Store in binlog text of statements that caused RBR events (47)
by worklog-noreply＠askmonty.org 25 May '10

25 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Store in binlog text of statements that caused RBR events CREATION DATE..: Sat, 15 Aug 2009, 23:48 SUPERVISOR.....: Monty IMPLEMENTOR....: COPIES TO......: Knielsen, Serg CATEGORY.......: Server-Sprint TASK ID........: 47 (http://askmonty.org/worklog/?tid=47) VERSION........: Server-9.x STATUS.........: Code-Review PRIORITY.......: 60 WORKED HOURS...: 31 ESTIMATE.......: 4 (hours remain) ORIG. ESTIMATE.: 35 PROGRESS NOTES: -=-=(Knielsen - Tue, 25 May 2010, 08:29)=-=- Help debug strange problem in mysqlbinlog.test. Worked 1 hour and estimate 4 hours remain (original estimate unchanged). -=-=(Knielsen - Mon, 17 May 2010, 08:45)=-=- Merge with latest trunk and run Buildbot tests. Worked 1 hour and estimate 5 hours remain (original estimate unchanged). -=-=(Knielsen - Wed, 05 May 2010, 13:53)=-=- Review of fixes to first review done. No new issues found. Worked 2 hours and estimate 6 hours remain (original estimate unchanged). -=-=(Knielsen - Fri, 23 Apr 2010, 12:51)=-=- Status updated. --- /tmp/wklog.47.old.28747 2010-04-23 12:51:36.000000000 +0000 +++ /tmp/wklog.47.new.28747 2010-04-23 12:51:36.000000000 +0000 @@ -1 +1 @@ -In-Progress +Code-Review -=-=(Knielsen - Tue, 06 Apr 2010, 15:26)=-=- Code review (mailed to maria-developers@). Worked 7 hours and estimate 8 hours remain (original estimate unchanged). -=-=(Knielsen - Tue, 06 Apr 2010, 15:25)=-=- Status updated. --- /tmp/wklog.47.old.12734 2010-04-06 15:25:54.000000000 +0000 +++ /tmp/wklog.47.new.12734 2010-04-06 15:25:54.000000000 +0000 @@ -1 +1 @@ -Code-Review +In-Progress -=-=(Knielsen - Mon, 29 Mar 2010, 10:59)=-=- Status updated. --- /tmp/wklog.47.old.27790 2010-03-29 10:59:53.000000000 +0000 +++ /tmp/wklog.47.new.27790 2010-03-29 10:59:53.000000000 +0000 @@ -1 +1 @@ -In-Progress +Code-Review -=-=(Alexi - Thu, 18 Feb 2010, 19:29)=-=- Worked 20 hours (alexi) Worked 20 hours and estimate 15 hours remain (original estimate unchanged). -=-=(Serg - Fri, 05 Feb 2010, 14:04)=-=- Observers changed: Knielsen,Serg -=-=(Guest - Fri, 05 Feb 2010, 13:40)=-=- Category updated. --- /tmp/wklog.47.old.9197 2010-02-05 13:40:36.000000000 +0200 +++ /tmp/wklog.47.new.9197 2010-02-05 13:40:36.000000000 +0200 @@ -1 +1 @@ -Server-RawIdeaBin +Server-Sprint ------------------------------------------------------------ -=-=(View All Progress Notes, 31 total)=-=- http://askmonty.org/worklog/index.pl?tid=47&nolimit=1 DESCRIPTION: Store in binlog (and show in mysqlbinlog output) texts of statements that caused RBR events This is needed for (list from Monty): - Easier to understand why updates happened - Would make it easier to find out where in application things went wrong (as you can search for exact strings) - Allow one to filter things based on comments in the statement. The cost of this can be that the binlog will be approximately 2x in size (especially insert of big blob's would be a bit painful), so this should be an optional feature. HIGH-LEVEL SPECIFICATION: Content ~~~~~~~ 1. Annotate_rows_log_event 2. Server option: --binlog-annotate-rows-events 3. Server option: --replicate-annotate-rows-events 4. mysqlbinlog option: --print-annotate-rows-events 5. mysqlbinlog output 1. Annotate_rows_log_event [ ANNOTATE_ROWS_EVENT ] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Describes the query which caused the corresponding rows events. Has empty post-header and contains the query text in its data part. Example: ************************ ANNOTATE_ROWS_EVENT ************************ 00000220 | B6 A0 2C 4B | time_when = 1261215926 00000224 | 33 | event_type = 51 00000225 | 64 00 00 00 | server_id = 100 00000229 | 36 00 00 00 | event_len = 54 0000022D | 56 02 00 00 | log_pos = 00000256 00000231 | 00 00 | flags = <none> ------------------------ 00000233 | 49 4E 53 45 | query = "INSERT INTO t1 VALUES (1), (2), (3)" 00000237 | 52 54 20 49 | 0000023B | 4E 54 4F 20 | 0000023F | 74 31 20 56 | 00000243 | 41 4C 55 45 | 00000247 | 53 20 28 31 | 0000024B | 29 2C 20 28 | 0000024F | 32 29 2C 20 | 00000253 | 28 33 29 | ************************ In binary log, Annotate_rows event follows the (possible) 'BEGIN' Query event and precedes the first of Table map events which accompany the corresponding rows events. (See example in the "mysqlbinlog output" section below.) 2. Server option: --binlog-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tells the master to write Annotate_rows events to the binary log. * Variable Name: binlog_annotate_rows_events * Scope: Global & Session * Access Type: Dynamic * Data Type: bool * Default Value: OFF NOTE. Session values allows to annotate only some selected statements: ... SET SESSION binlog_annotate_rows_events=ON; ... statements to be annotated ... SET SESSION binlog_annotate_rows_events=OFF; ... statements not to be annotated ... 3. Server option: --replicate-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Tells the slave to reproduce Annotate_rows events recieved from the master in its own binary log (sensible only in pair with log-slave-updates option). * Variable Name: replicate_annotate_rows_events * Scope: Global * Access Type: Read only * Data Type: bool * Default Value: OFF NOTE. Why do we additionally need this 'replicate' option? Why not to make the slave to reproduce this events when its binlog-annotate-rows-events global value is ON? Well, because, for example, we may want to configure the slave which should reproduce Annotate_rows events but has global binlog-annotate-rows-events = OFF meaning this to be the default value for the client threads (see also "How slave treats replicate-annotate-rows-events option" in LLD part). 4. mysqlbinlog option: --print-annotate-rows-events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ With this option, mysqlbinlog prints the content of Annotate_rows events (if the binary log does contain them). Without this option (i.e. by default), mysqlbinlog skips Annotate_rows events. 5. mysqlbinlog output ~~~~~~~~~~~~~~~~~~~~~ With --print-annotate-rows-events, mysqlbinlog outputs Annotate_rows events in a form like this: ... # at 1646 #091219 12:45:26 server id 100 end_log_pos 1714 Query thread_id=1 exec_time=0 error_code=0 SET TIMESTAMP=1261215926/*!*/; BEGIN /*!*/; # at 1714 # at 1812 # at 1853 # at 1894 # at 1938 #091219 12:45:26 server id 100 end_log_pos 1812 Query: `DELETE t1, t2 FROM t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.a=t2.a AND t2.a=t3.a` #091219 12:45:26 server id 100 end_log_pos 1853 Table_map: `test`.`t1` mapped to number 16 #091219 12:45:26 server id 100 end_log_pos 1894 Table_map: `test`.`t2` mapped to number 17 #091219 12:45:26 server id 100 end_log_pos 1938 Delete_rows: table id 16 #091219 12:45:26 server id 100 end_log_pos 1982 Delete_rows: table id 17 flags: STMT_END_F ... LOW-LEVEL DESIGN: Content ~~~~~~~ 1. Annotate_rows event number 2. Outline of Annotate_rows event behavior 3. How Master writes Annotate_rows events to the binary log 4. How slave treats replicate-annotate-rows-events option 5. How slave IO thread requests Annotate_rows events 6. How master executes the request 7. How slave SQL thread processes Annotate_rows events 8. General remarks 1. Annotate_rows event number ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To avoid possible event numbers conflict with MySQL/Sun, we leave a gap between the last MySQL event number and the Annotate_rows event number: enum Log_event_type { ... INCIDENT_EVENT= 26, // New MySQL event numbers are to be added here MYSQL_EVENTS_END, MARIA_EVENTS_BEGIN= 51, // New Maria event numbers start from here ANNOTATE_ROWS_EVENT= 51, ENUM_END_EVENT }; together with the corresponding extension of 'post_header_len' array in the Format description event. (This extension does not affect the compatibility of the binary log). Here is how Format description event looks like with this extension: ************************ FORMAT_DESCRIPTION_EVENT ************************ 00000004 | A1 A0 2C 4B | time_when = 1261215905 00000008 | 0F | event_type = 15 00000009 | 64 00 00 00 | server_id = 100 0000000D | 7F 00 00 00 | event_len = 127 00000011 | 83 00 00 00 | log_pos = 00000083 00000015 | 01 00 | flags = LOG_EVENT_BINLOG_IN_USE_F ------------------------ 00000017 | 04 00 | binlog_ver = 4 00000019 | 35 2E 32 2E | server_ver = 5.2.0-MariaDB-alpha-debug-log ..... ... 0000004B | A1 A0 2C 4B | time_created = 1261215905 0000004F | 13 | common_header_len = 19 ------------------------ post_header_len ------------------------ 00000050 | 38 | 56 - START_EVENT_V3 [1] ..... ... 00000069 | 02 | 2 - INCIDENT_EVENT [26] 0000006A | 00 | 0 - RESERVED [27] ..... ... 00000081 | 00 | 0 - RESERVED [50] 00000082 | 00 | 0 - ANNOTATE_ROWS_EVENT [51] ************************ 2. Outline of Annotate_rows event behavior ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Each Annotate_rows_log_event object has two private members describing the corresponding query: char *m_query_txt; uint m_query_len; When the object is created for writing to a binary log, this query is taken from 'thd' (for short, below we omit the 'Annotate_rows_log_event::' prefix as well as other implementation details): Annotate_rows_log_event(THD *thd) { m_query_txt = thd->query(); m_query_len = thd->query_length(); } When the object is read from a binary log, the query is taken from the buffer containing the binary log representation of the event (this buffer is allocated in Log_event object from which all Log events are derived): Annotate_rows_log_event(char *buf, uint event_len, Format_description_log_event *desc) { m_query_len = event_len - desc->common_header_len; m_query_txt = buf + desc->common_header_len; } The events are written to the binary log by the Log_event::write() member which calls virtual write_data_header() and write_data_body() members ("data header" and "post header" are synonym in replication terminology). In our case, data header is empty and data body is just the query: bool write_data_body(IO_CACHE *file) { return my_b_safe_write(file, (uchar*) m_query_txt, m_query_len); } Printing the event is just printing the query: void Annotate_rows_log_event::print(FILE *file, PRINT_EVENT_INFO *pinfo) { my_b_printf(&pinfo->head_cache, "\tQuery: `%s`\n", m_query_txt); } 3. How Master writes Annotate_rows events to the binary log ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The event is written to the binary log just before the group of Table_map events which precede corresponding Rows events (one query may generate several Table map events in the binary log, but the corresponding Annotate_rows event must be written only once before the first Table map event; hence the boolean variable 'with_annotate' below): int write_locked_table_maps(THD *thd) { ... bool with_annotate= thd->variables.binlog_annotate_rows_events; ... for (uint i= 0; i < ... <number of tables> ...; ++i) { ... thd->binlog_write_table_map(table, ..., with_annotate); with_annotate= 0; // write Annotate_event not more than once ... } ... } int THD::binlog_write_table_map(TABLE *table, ..., bool with_annotate) { ... Table_map_log_event the_event(...); ... if (with_annotate) { Annotate_rows_log_event anno(this); mysql_bin_log.write(&anno); } mysql_bin_log.write(&the_event); ... } 4. How slave treats replicate-annotate-rows-events option ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The replicate-annotate-rows-events option is treated just as the session value of the binlog_annotate_rows_events variable for the slave IO and SQL threads. This setting is done during initialization of these threads: pthread_handler_t handle_slave_io(void *arg) { THD *thd= new THD; ... init_slave_thread(thd, SLAVE_THD_IO); ... } pthread_handler_t handle_slave_sql(void *arg) { THD *thd= new THD; ... init_slave_thread(thd, SLAVE_THD_SQL); ... } int init_slave_thread(THD* thd, SLAVE_THD_TYPE thd_type) { ... thd->variables.binlog_annotate_rows_events= opt_replicate_annotate_rows_events; ... } 5. How slave IO thread requests Annotate_rows events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If the replicate-annotate-rows-events option is not set on a slave, there is no need for master to send Annotate_rows events to this slave. The slave (or mysqlbinlog in remote case), before requesting binlog dump via the COM_BINLOG_DUMP command, informs the master whether it should send these events by executing the newly added COM_BINLOG_DUMP_OPTIONS_EXT server command: case COM_BINLOG_DUMP_OPTIONS_EXT: thd->binlog_dump_flags_ext= packet[0]; my_ok(thd); break; Note. We add this new command and don't use COM_BINLOG_DUMP to avoid possible conflicts with MySQL/Sun. 6. How master executes the request ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ case COM_BINLOG_DUMP: { ... flags= uint2korr(packet + 4); ... mysql_binlog_send(thd, ..., flags); ... } void mysql_binlog_send(THD* thd, ..., ushort flags) { ... Log_event::read_log_event(&log, packet, ...); ... if ((*packet)[EVENT_TYPE_OFFSET + 1] != ANNOTATE_ROWS_EVENT || flags & BINLOG_SEND_ANNOTATE_ROWS_EVENT) { my_net_write(net, packet->ptr(), packet->length()); } ... } 7. How slave SQL thread processes Annotate_rows events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The slave processes each recieved event by "applying" it, i.e. by calling the Log_event::apply_event() function which in turn calls the virtual do_apply_event() member specific for each type of the event. int exec_relay_log_event(THD* thd, Relay_log_info* rli) { ... Log_event *ev = next_event(rli); ... apply_event_and_update_pos(ev, ...); if (ev->get_type_code() != FORMAT_DESCRIPTION_EVENT) delete ev; ... } int apply_event_and_update_pos(Log_event *ev, ...) { ... ev->apply_event(...); ... } int Log_event::apply_event(...) { return do_apply_event(...); } What does it mean to "apply" an Annotate_rows event? It means to set current thd query to that of the described by the event, i.e. to the query which caused the subsequent Rows events (see "How Master writes Annotate_rows events to the binary log" to follow what happens further when the subsequent Rows events are applied): int Annotate_rows_log_event::do_apply_event(...) { thd->set_query(m_query_txt, m_query_len); } NOTE. I am not sure, but possibly current values of thd->query and thd->query_length should be saved before calling set_query() and to be restored on the Annotate_rows_log_event object deletion. Is it really needed ? After calling this do_apply_event() function we may not delete the Annotate_rows_log_event object immediatedly (see exec_relay_log_event() above) because thd->query now points to the string inside this object. We may keep the pointer to this object in the Relay_log_info: class Relay_log_info { public: ... void set_annotate_event(Annotate_rows_log_event*); Annotate_rows_log_event* get_annotate_event(); void free_annotate_event(); ... private: Annotate_rows_log_event* m_annotate_event; }; The saved Annotate_rows object should be deleted when all corresponding Rows events will be processed: int exec_relay_log_event(THD* thd, Relay_log_info* rli) { ... Log_event *ev= next_event(rli); ... apply_event_and_update_pos(ev, ...); if (rli->get_annotate_event() && is_last_rows_event(ev)) rli->free_annotate_event(); else if (ev->get_type_code() == ANNOTATE_ROWS_EVENT) rli->set_annotate_event((Annotate_rows_log_event*) ev); else if (ev->get_type_code() != FORMAT_DESCRIPTION_EVENT) delete ev; ... } where bool is_last_rows_event(Log_event* ev) { Log_event_type type= ev->get_type_code(); if (IS_ROWS_EVENT_TYPE(type)) { Rows_log_event* rows= (Rows_log_event*)ev; return rows->get_flags(Rows_log_event::STMT_END_F); } return 0; } #define IS_ROWS_EVENT_TYPE(type) ((type) == WRITE_ROWS_EVENT || \ (type) == UPDATE_ROWS_EVENT || \ (type) == DELETE_ROWS_EVENT) 8. General remarks ~~~~~~~~~~~~~~~~~~ Kristian noticed that introducing new log event type should be coordinated somehow with MySQL/Sun: Kristian: The numeric code for this event must be assigned carefully. It should be coordinated with MySQL/Sun, otherwise we can get into a situation where MySQL uses the same numeric code for one event that MariaDB uses for ANNOTATE_ROWS_EVENT, which would make merging the two impossible. Alex: I reserved about 20 numbers not to have possible conflicts with MySQL. Kristian: Still, I think it would be appropriate to send a polite email to internals(a)lists.mysql.com about this and suggesting to reserve the event number. ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

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[Maria-developers] Progress (by Knielsen): Efficient group commit for binary log (116)
by worklog-noreply＠askmonty.org 25 May '10

25 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Efficient group commit for binary log CREATION DATE..: Mon, 26 Apr 2010, 13:28 SUPERVISOR.....: Knielsen IMPLEMENTOR....: COPIES TO......: Serg CATEGORY.......: Server-RawIdeaBin TASK ID........: 116 (http://askmonty.org/worklog/?tid=116) VERSION........: Server-9.x STATUS.........: Un-Assigned PRIORITY.......: 60 WORKED HOURS...: 49 ESTIMATE.......: 0 (hours remain) ORIG. ESTIMATE.: 0 PROGRESS NOTES: -=-=(Knielsen - Tue, 25 May 2010, 08:28)=-=- More thoughts on and changes to the archtecture. Got to something now that I am satisfied with and that seems to be able to handle all issues. Implement new prepare_ordered and commit_ordered handler methods and the logic in ha_commit_trans(). Implement TC_LOG::group_log_xid() method and logic in ha_commit_trans(). Implement XtraDB part, using commit_ordered() rather than prepare_commit_mutex. Fix test suite failures. Proof-of-concept patch series complete now. Do initial benchmark, getting good results. With 64 threads, see 26x improvement in queries-per-sec. Next step: write up the architecture description. Worked 21 hours and estimate 0 hours remain (original estimate increased by 21 hours). -=-=(Knielsen - Wed, 12 May 2010, 06:41)=-=- Started work on a Quilt patch series, refactoring the binlog code to prepare for implementing the group commit, and working on the design of group commit in parallel. Found and fixed several problems in error handling when writing to binlog. Removed redundant table map version locking. Split binlog writing into two parts in preparations for group commit. When ready to write to the binlog, threads enter a queue, and the first thread in the queue handles the binlog writing for everyone. When it obtains the LOCK_log, it first loops over all threads, executing the first part of binlog writing (the write(2) syscall essentially). It then runs the second part (fsync(2) essentially) only once, and then wakes up the remaining threads in the queue. Still to be done: Finish the proof-of-concept group commit patch, by 1) implementing the prepare_fast() and commit_fast() callbacks in handler.cc 2) move the binlog thread enqueue from log_xid() to binlog_prepare_fast(), 3) move fast part of InnoDB commit to innobase_commit_fast(), removing the prepare_commit_mutex(). Write up the final design in this worklog. Evaluate the design to see if we can do better/different. Think about possible next steps, such as releasing innodb row locks early (in innobase_prepare_fast), and doing crash recovery by replaying transactions from the binlog (removing the need for engine durability and 2 of 3 fsync() in commit). Worked 28 hours and estimate 0 hours remain (original estimate increased by 28 hours). -=-=(Serg - Mon, 26 Apr 2010, 14:10)=-=- Observers changed: Serg DESCRIPTION: Currently, in order to ensure that the server can recover after a crash to a state in which storage engines and binary log are consistent with each other, it is necessary to use XA with durable commits for both storage engines (innodb_flush_log_at_trx_commit=1) and binary log (sync_binlog=1). This is _very_ expensive, since the server needs to do three fsync() operations for every commit, as there is no working group commit when the binary log is enabled. The idea is to - Implement/fix group commit to work properly with the binary log enabled. - (Optionally) avoid the need to fsync() in the engine, and instead rely on replaying any lost transactions from the binary log against the engine during crash recovery. For background see these articles: http://kristiannielsen.livejournal.com/12254.html http://kristiannielsen.livejournal.com/12408.html http://kristiannielsen.livejournal.com/12553.html ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

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[Maria-developers] Progress (by Knielsen): Efficient group commit for binary log (116)
by worklog-noreply＠askmonty.org 25 May '10

25 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Efficient group commit for binary log CREATION DATE..: Mon, 26 Apr 2010, 13:28 SUPERVISOR.....: Knielsen IMPLEMENTOR....: COPIES TO......: Serg CATEGORY.......: Server-RawIdeaBin TASK ID........: 116 (http://askmonty.org/worklog/?tid=116) VERSION........: Server-9.x STATUS.........: Un-Assigned PRIORITY.......: 60 WORKED HOURS...: 49 ESTIMATE.......: 0 (hours remain) ORIG. ESTIMATE.: 0 PROGRESS NOTES: -=-=(Knielsen - Tue, 25 May 2010, 08:28)=-=- More thoughts on and changes to the archtecture. Got to something now that I am satisfied with and that seems to be able to handle all issues. Implement new prepare_ordered and commit_ordered handler methods and the logic in ha_commit_trans(). Implement TC_LOG::group_log_xid() method and logic in ha_commit_trans(). Implement XtraDB part, using commit_ordered() rather than prepare_commit_mutex. Fix test suite failures. Proof-of-concept patch series complete now. Do initial benchmark, getting good results. With 64 threads, see 26x improvement in queries-per-sec. Next step: write up the architecture description. Worked 21 hours and estimate 0 hours remain (original estimate increased by 21 hours). -=-=(Knielsen - Wed, 12 May 2010, 06:41)=-=- Started work on a Quilt patch series, refactoring the binlog code to prepare for implementing the group commit, and working on the design of group commit in parallel. Found and fixed several problems in error handling when writing to binlog. Removed redundant table map version locking. Split binlog writing into two parts in preparations for group commit. When ready to write to the binlog, threads enter a queue, and the first thread in the queue handles the binlog writing for everyone. When it obtains the LOCK_log, it first loops over all threads, executing the first part of binlog writing (the write(2) syscall essentially). It then runs the second part (fsync(2) essentially) only once, and then wakes up the remaining threads in the queue. Still to be done: Finish the proof-of-concept group commit patch, by 1) implementing the prepare_fast() and commit_fast() callbacks in handler.cc 2) move the binlog thread enqueue from log_xid() to binlog_prepare_fast(), 3) move fast part of InnoDB commit to innobase_commit_fast(), removing the prepare_commit_mutex(). Write up the final design in this worklog. Evaluate the design to see if we can do better/different. Think about possible next steps, such as releasing innodb row locks early (in innobase_prepare_fast), and doing crash recovery by replaying transactions from the binlog (removing the need for engine durability and 2 of 3 fsync() in commit). Worked 28 hours and estimate 0 hours remain (original estimate increased by 28 hours). -=-=(Serg - Mon, 26 Apr 2010, 14:10)=-=- Observers changed: Serg DESCRIPTION: Currently, in order to ensure that the server can recover after a crash to a state in which storage engines and binary log are consistent with each other, it is necessary to use XA with durable commits for both storage engines (innodb_flush_log_at_trx_commit=1) and binary log (sync_binlog=1). This is _very_ expensive, since the server needs to do three fsync() operations for every commit, as there is no working group commit when the binary log is enabled. The idea is to - Implement/fix group commit to work properly with the binary log enabled. - (Optionally) avoid the need to fsync() in the engine, and instead rely on replaying any lost transactions from the binary log against the engine during crash recovery. For background see these articles: http://kristiannielsen.livejournal.com/12254.html http://kristiannielsen.livejournal.com/12408.html http://kristiannielsen.livejournal.com/12553.html ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

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[Maria-developers] Updated (by Psergey): Push conditions down into non-mergeable VIEWs when possible (119)
by worklog-noreply＠askmonty.org 25 May '10

25 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Push conditions down into non-mergeable VIEWs when possible CREATION DATE..: Mon, 24 May 2010, 20:52 SUPERVISOR.....: Igor IMPLEMENTOR....: COPIES TO......: Psergey, Timour CATEGORY.......: Server-RawIdeaBin TASK ID........: 119 (http://askmonty.org/worklog/?tid=119) VERSION........: Server-9.x STATUS.........: Un-Assigned PRIORITY.......: 60 WORKED HOURS...: 0 ESTIMATE.......: 0 (hours remain) ORIG. ESTIMATE.: 0 PROGRESS NOTES: -=-=(Psergey - Mon, 24 May 2010, 20:59)=-=- High-Level Specification modified. --- /tmp/wklog.119.old.25116 2010-05-24 20:59:40.000000000 +0000 +++ /tmp/wklog.119.new.25116 2010-05-24 20:59:40.000000000 +0000 @@ -1 +1,113 @@ +<contents> +HLS +1. Problems to be addressed in this WL +2. Pushdown of conditions into non-mergeable VIEWs +2.1 A note about VIEWs with ORDER BY ... LIMIT +2.2 What condition can be pushed +3. Pushdown from HAVING into WHERE +4. When to do the pushdown +5. Other things to take care of + + +</contents> + +1. Problems to be addressed in this WL +====================================== +The problem actually consists of two parts: +1. Condition on VIEW columns are not pushed down into VIEWs. +2. Even if conditions were pushed, they would have been put into VIEW's +HAVING clause, which would not give enough of speedup. In order to get a +real speedup, the optimizer must be able to move relevant part of HAVING +into WHERE (and then use it for further optimizations) in order to provide +the desired speedup. Note that HAVING->WHERE condition move is orthogonal +to VIEW processing. + +2. Pushdown of conditions into non-mergeable VIEWs +================================================== +We can push a condition into non-mergeable VIEW when VIEW's top-most operation +is selection (i.e., filtering). This is true, for example, when the VIEW is +defined as + + SELECT select_list FROM from_clause [WHERE where_cond] [HAVING having_cond] + +and not true when the VIEW is defined as + + SELECT select_list FROM from_clause [WHERE where_cond] ORDER BY expr LIMIT n + +Generalizing the above, we arrive at the following rule: + + For non-mergeable VIEWs, + - pushdown must not be done if VIEW uses ORDER BY .. LIMIT + - when pushdown is done, the pushed condition should be added to the WHERE + clause. + +Note: In scope of this WL, we will not hande VIEWs that have UNION [ALL] as +top operation. + +(TODO: what about SELECT DISTINCT?) +(TODO: pushdown down into IN subqueries?) + +2.1 A note about VIEWs with ORDER BY ... LIMIT +---------------------------------------------- +Although it is not possible to push a condition below the ORDER BY ... LIMIT +operation, there is still some benefit from checking the condition early as +that would allow to avoid writing non-matching rows into temporary table. + +We could do that if we introduced a post-ORDERBY selection operation. That +operation would also allow to support ORDER BY ... LIMIT inside subqueries +(we don't currently support those because default subquery strategy, +IN->EXISTS rewrite, also needs to push a condition into subquery). + +2.2 What condition can be pushed +-------------------------------- +Assuming simplify_joins() operation has done normalization: +* If the VIEW is in top-level join list, or inside a semi-join that's in + top-level join list, we can push parts of WHERE condition. +* If the VIEW is inside an outer join, we can push it's ON expression. + +We can reuse make_cond_for_index()/make_remainder_cond() code to extract part +of condition that can be pushed, and the remainder, respectively. + +Pushability criteria for an atomic (i.e. not AND/OR) condition is that + + the condition only uses VIEW's fields. + +(TODO: what about fields of const tables? Do we have const tables already +retrived by the time VIEW is materialized? If yes, we could push down +expressions that refer to const tables, too) + +3. Pushdown from HAVING into WHERE +================================== +The idea is: + + Parts of HAVING that refer to columns/expressions we're doing GROUP BY on + can be put into WHERE. + +(TODO: do we need to handle case of grouping over expressions?) + +(TODO: when moving expression for HAVING to WHERE, do we need +to do something with it? Replace all Item_ref objects with items that +they refer to? + - In case of referring to expression, do we get + Item_ref(where_clause_expr) or expr( Item_ref(..), .., Item_ref(..))? +) + +4. When to do the pushdown +========================== +In order to do pushdown, we must have prepare phase finished +for both parent (so that we can make sense of its WHERE condition) and +child (so that we know what it has in its select list). + +We can do pushdown before we've done join optimization (i.e. choose_plan() +call) of the parent. + +We must do pushdown before we've done JOIN::optimize() of the child +(in particular, it must be done before we do update_ref_and_keys() and +range analysis in the child). + + +5. Other things to take care of +=============================== +* Pushing down fulltext predicates (it seems one needs to "register" a + fulltext predicate when it is moved from one select from another? Ask Serg) DESCRIPTION: There are complaints (see links below) about cases with non-mergeable VIEW (because it has a GROUP BY), a query that has restrictions on the grouped column, and poor performance that is caused by VIEW processing code ignoring the restriction. This WL is about addressing this issue. links to complaints: http://code.openark.org/blog/mysql/views-better-performance-with-condition-… http://www.mysqlperformanceblog.com/2010/05/19/a-workaround-for-the-perform… The target version is MariaDB 5.3+, because it has late optimization/execution for FROM-subqueries/non mergeable VIEWs, which makes it much more feasible to inject something into VIEW before it is optimized/executed. HIGH-LEVEL SPECIFICATION: <contents> HLS 1. Problems to be addressed in this WL 2. Pushdown of conditions into non-mergeable VIEWs 2.1 A note about VIEWs with ORDER BY ... LIMIT 2.2 What condition can be pushed 3. Pushdown from HAVING into WHERE 4. When to do the pushdown 5. Other things to take care of </contents> 1. Problems to be addressed in this WL ====================================== The problem actually consists of two parts: 1. Condition on VIEW columns are not pushed down into VIEWs. 2. Even if conditions were pushed, they would have been put into VIEW's HAVING clause, which would not give enough of speedup. In order to get a real speedup, the optimizer must be able to move relevant part of HAVING into WHERE (and then use it for further optimizations) in order to provide the desired speedup. Note that HAVING->WHERE condition move is orthogonal to VIEW processing. 2. Pushdown of conditions into non-mergeable VIEWs ================================================== We can push a condition into non-mergeable VIEW when VIEW's top-most operation is selection (i.e., filtering). This is true, for example, when the VIEW is defined as SELECT select_list FROM from_clause [WHERE where_cond] [HAVING having_cond] and not true when the VIEW is defined as SELECT select_list FROM from_clause [WHERE where_cond] ORDER BY expr LIMIT n Generalizing the above, we arrive at the following rule: For non-mergeable VIEWs, - pushdown must not be done if VIEW uses ORDER BY .. LIMIT - when pushdown is done, the pushed condition should be added to the WHERE clause. Note: In scope of this WL, we will not hande VIEWs that have UNION [ALL] as top operation. (TODO: what about SELECT DISTINCT?) (TODO: pushdown down into IN subqueries?) 2.1 A note about VIEWs with ORDER BY ... LIMIT ---------------------------------------------- Although it is not possible to push a condition below the ORDER BY ... LIMIT operation, there is still some benefit from checking the condition early as that would allow to avoid writing non-matching rows into temporary table. We could do that if we introduced a post-ORDERBY selection operation. That operation would also allow to support ORDER BY ... LIMIT inside subqueries (we don't currently support those because default subquery strategy, IN->EXISTS rewrite, also needs to push a condition into subquery). 2.2 What condition can be pushed -------------------------------- Assuming simplify_joins() operation has done normalization: * If the VIEW is in top-level join list, or inside a semi-join that's in top-level join list, we can push parts of WHERE condition. * If the VIEW is inside an outer join, we can push it's ON expression. We can reuse make_cond_for_index()/make_remainder_cond() code to extract part of condition that can be pushed, and the remainder, respectively. Pushability criteria for an atomic (i.e. not AND/OR) condition is that the condition only uses VIEW's fields. (TODO: what about fields of const tables? Do we have const tables already retrived by the time VIEW is materialized? If yes, we could push down expressions that refer to const tables, too) 3. Pushdown from HAVING into WHERE ================================== The idea is: Parts of HAVING that refer to columns/expressions we're doing GROUP BY on can be put into WHERE. (TODO: do we need to handle case of grouping over expressions?) (TODO: when moving expression for HAVING to WHERE, do we need to do something with it? Replace all Item_ref objects with items that they refer to? - In case of referring to expression, do we get Item_ref(where_clause_expr) or expr( Item_ref(..), .., Item_ref(..))? ) 4. When to do the pushdown ========================== In order to do pushdown, we must have prepare phase finished for both parent (so that we can make sense of its WHERE condition) and child (so that we know what it has in its select list). We can do pushdown before we've done join optimization (i.e. choose_plan() call) of the parent. We must do pushdown before we've done JOIN::optimize() of the child (in particular, it must be done before we do update_ref_and_keys() and range analysis in the child). 5. Other things to take care of =============================== * Pushing down fulltext predicates (it seems one needs to "register" a fulltext predicate when it is moved from one select from another? Ask Serg) ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

3 2

[Maria-developers] Updated (by Psergey): Push conditions down into non-mergeable VIEWs when possible (119)
by worklog-noreply＠askmonty.org 24 May '10

24 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Push conditions down into non-mergeable VIEWs when possible CREATION DATE..: Mon, 24 May 2010, 20:52 SUPERVISOR.....: Igor IMPLEMENTOR....: COPIES TO......: Psergey, Timour CATEGORY.......: Server-RawIdeaBin TASK ID........: 119 (http://askmonty.org/worklog/?tid=119) VERSION........: Server-9.x STATUS.........: Un-Assigned PRIORITY.......: 60 WORKED HOURS...: 0 ESTIMATE.......: 0 (hours remain) ORIG. ESTIMATE.: 0 PROGRESS NOTES: -=-=(Psergey - Mon, 24 May 2010, 20:59)=-=- High-Level Specification modified. --- /tmp/wklog.119.old.25116 2010-05-24 20:59:40.000000000 +0000 +++ /tmp/wklog.119.new.25116 2010-05-24 20:59:40.000000000 +0000 @@ -1 +1,113 @@ +<contents> +HLS +1. Problems to be addressed in this WL +2. Pushdown of conditions into non-mergeable VIEWs +2.1 A note about VIEWs with ORDER BY ... LIMIT +2.2 What condition can be pushed +3. Pushdown from HAVING into WHERE +4. When to do the pushdown +5. Other things to take care of + + +</contents> + +1. Problems to be addressed in this WL +====================================== +The problem actually consists of two parts: +1. Condition on VIEW columns are not pushed down into VIEWs. +2. Even if conditions were pushed, they would have been put into VIEW's +HAVING clause, which would not give enough of speedup. In order to get a +real speedup, the optimizer must be able to move relevant part of HAVING +into WHERE (and then use it for further optimizations) in order to provide +the desired speedup. Note that HAVING->WHERE condition move is orthogonal +to VIEW processing. + +2. Pushdown of conditions into non-mergeable VIEWs +================================================== +We can push a condition into non-mergeable VIEW when VIEW's top-most operation +is selection (i.e., filtering). This is true, for example, when the VIEW is +defined as + + SELECT select_list FROM from_clause [WHERE where_cond] [HAVING having_cond] + +and not true when the VIEW is defined as + + SELECT select_list FROM from_clause [WHERE where_cond] ORDER BY expr LIMIT n + +Generalizing the above, we arrive at the following rule: + + For non-mergeable VIEWs, + - pushdown must not be done if VIEW uses ORDER BY .. LIMIT + - when pushdown is done, the pushed condition should be added to the WHERE + clause. + +Note: In scope of this WL, we will not hande VIEWs that have UNION [ALL] as +top operation. + +(TODO: what about SELECT DISTINCT?) +(TODO: pushdown down into IN subqueries?) + +2.1 A note about VIEWs with ORDER BY ... LIMIT +---------------------------------------------- +Although it is not possible to push a condition below the ORDER BY ... LIMIT +operation, there is still some benefit from checking the condition early as +that would allow to avoid writing non-matching rows into temporary table. + +We could do that if we introduced a post-ORDERBY selection operation. That +operation would also allow to support ORDER BY ... LIMIT inside subqueries +(we don't currently support those because default subquery strategy, +IN->EXISTS rewrite, also needs to push a condition into subquery). + +2.2 What condition can be pushed +-------------------------------- +Assuming simplify_joins() operation has done normalization: +* If the VIEW is in top-level join list, or inside a semi-join that's in + top-level join list, we can push parts of WHERE condition. +* If the VIEW is inside an outer join, we can push it's ON expression. + +We can reuse make_cond_for_index()/make_remainder_cond() code to extract part +of condition that can be pushed, and the remainder, respectively. + +Pushability criteria for an atomic (i.e. not AND/OR) condition is that + + the condition only uses VIEW's fields. + +(TODO: what about fields of const tables? Do we have const tables already +retrived by the time VIEW is materialized? If yes, we could push down +expressions that refer to const tables, too) + +3. Pushdown from HAVING into WHERE +================================== +The idea is: + + Parts of HAVING that refer to columns/expressions we're doing GROUP BY on + can be put into WHERE. + +(TODO: do we need to handle case of grouping over expressions?) + +(TODO: when moving expression for HAVING to WHERE, do we need +to do something with it? Replace all Item_ref objects with items that +they refer to? + - In case of referring to expression, do we get + Item_ref(where_clause_expr) or expr( Item_ref(..), .., Item_ref(..))? +) + +4. When to do the pushdown +========================== +In order to do pushdown, we must have prepare phase finished +for both parent (so that we can make sense of its WHERE condition) and +child (so that we know what it has in its select list). + +We can do pushdown before we've done join optimization (i.e. choose_plan() +call) of the parent. + +We must do pushdown before we've done JOIN::optimize() of the child +(in particular, it must be done before we do update_ref_and_keys() and +range analysis in the child). + + +5. Other things to take care of +=============================== +* Pushing down fulltext predicates (it seems one needs to "register" a + fulltext predicate when it is moved from one select from another? Ask Serg) DESCRIPTION: There are complaints (see links below) about cases with non-mergeable VIEW (because it has a GROUP BY), a query that has restrictions on the grouped column, and poor performance that is caused by VIEW processing code ignoring the restriction. This WL is about addressing this issue. links to complaints: http://code.openark.org/blog/mysql/views-better-performance-with-condition-… http://www.mysqlperformanceblog.com/2010/05/19/a-workaround-for-the-perform… The target version is MariaDB 5.3+, because it has late optimization/execution for FROM-subqueries/non mergeable VIEWs, which makes it much more feasible to inject something into VIEW before it is optimized/executed. HIGH-LEVEL SPECIFICATION: <contents> HLS 1. Problems to be addressed in this WL 2. Pushdown of conditions into non-mergeable VIEWs 2.1 A note about VIEWs with ORDER BY ... LIMIT 2.2 What condition can be pushed 3. Pushdown from HAVING into WHERE 4. When to do the pushdown 5. Other things to take care of </contents> 1. Problems to be addressed in this WL ====================================== The problem actually consists of two parts: 1. Condition on VIEW columns are not pushed down into VIEWs. 2. Even if conditions were pushed, they would have been put into VIEW's HAVING clause, which would not give enough of speedup. In order to get a real speedup, the optimizer must be able to move relevant part of HAVING into WHERE (and then use it for further optimizations) in order to provide the desired speedup. Note that HAVING->WHERE condition move is orthogonal to VIEW processing. 2. Pushdown of conditions into non-mergeable VIEWs ================================================== We can push a condition into non-mergeable VIEW when VIEW's top-most operation is selection (i.e., filtering). This is true, for example, when the VIEW is defined as SELECT select_list FROM from_clause [WHERE where_cond] [HAVING having_cond] and not true when the VIEW is defined as SELECT select_list FROM from_clause [WHERE where_cond] ORDER BY expr LIMIT n Generalizing the above, we arrive at the following rule: For non-mergeable VIEWs, - pushdown must not be done if VIEW uses ORDER BY .. LIMIT - when pushdown is done, the pushed condition should be added to the WHERE clause. Note: In scope of this WL, we will not hande VIEWs that have UNION [ALL] as top operation. (TODO: what about SELECT DISTINCT?) (TODO: pushdown down into IN subqueries?) 2.1 A note about VIEWs with ORDER BY ... LIMIT ---------------------------------------------- Although it is not possible to push a condition below the ORDER BY ... LIMIT operation, there is still some benefit from checking the condition early as that would allow to avoid writing non-matching rows into temporary table. We could do that if we introduced a post-ORDERBY selection operation. That operation would also allow to support ORDER BY ... LIMIT inside subqueries (we don't currently support those because default subquery strategy, IN->EXISTS rewrite, also needs to push a condition into subquery). 2.2 What condition can be pushed -------------------------------- Assuming simplify_joins() operation has done normalization: * If the VIEW is in top-level join list, or inside a semi-join that's in top-level join list, we can push parts of WHERE condition. * If the VIEW is inside an outer join, we can push it's ON expression. We can reuse make_cond_for_index()/make_remainder_cond() code to extract part of condition that can be pushed, and the remainder, respectively. Pushability criteria for an atomic (i.e. not AND/OR) condition is that the condition only uses VIEW's fields. (TODO: what about fields of const tables? Do we have const tables already retrived by the time VIEW is materialized? If yes, we could push down expressions that refer to const tables, too) 3. Pushdown from HAVING into WHERE ================================== The idea is: Parts of HAVING that refer to columns/expressions we're doing GROUP BY on can be put into WHERE. (TODO: do we need to handle case of grouping over expressions?) (TODO: when moving expression for HAVING to WHERE, do we need to do something with it? Replace all Item_ref objects with items that they refer to? - In case of referring to expression, do we get Item_ref(where_clause_expr) or expr( Item_ref(..), .., Item_ref(..))? ) 4. When to do the pushdown ========================== In order to do pushdown, we must have prepare phase finished for both parent (so that we can make sense of its WHERE condition) and child (so that we know what it has in its select list). We can do pushdown before we've done join optimization (i.e. choose_plan() call) of the parent. We must do pushdown before we've done JOIN::optimize() of the child (in particular, it must be done before we do update_ref_and_keys() and range analysis in the child). 5. Other things to take care of =============================== * Pushing down fulltext predicates (it seems one needs to "register" a fulltext predicate when it is moved from one select from another? Ask Serg) ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

1 0

[Maria-developers] Updated (by Psergey): Push conditions down into non-mergeable VIEWs when possible (119)
by worklog-noreply＠askmonty.org 24 May '10

24 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Push conditions down into non-mergeable VIEWs when possible CREATION DATE..: Mon, 24 May 2010, 20:52 SUPERVISOR.....: Igor IMPLEMENTOR....: COPIES TO......: Psergey, Timour CATEGORY.......: Server-RawIdeaBin TASK ID........: 119 (http://askmonty.org/worklog/?tid=119) VERSION........: Server-9.x STATUS.........: Un-Assigned PRIORITY.......: 60 WORKED HOURS...: 0 ESTIMATE.......: 0 (hours remain) ORIG. ESTIMATE.: 0 PROGRESS NOTES: -=-=(Psergey - Mon, 24 May 2010, 20:59)=-=- High-Level Specification modified. --- /tmp/wklog.119.old.25116 2010-05-24 20:59:40.000000000 +0000 +++ /tmp/wklog.119.new.25116 2010-05-24 20:59:40.000000000 +0000 @@ -1 +1,113 @@ +<contents> +HLS +1. Problems to be addressed in this WL +2. Pushdown of conditions into non-mergeable VIEWs +2.1 A note about VIEWs with ORDER BY ... LIMIT +2.2 What condition can be pushed +3. Pushdown from HAVING into WHERE +4. When to do the pushdown +5. Other things to take care of + + +</contents> + +1. Problems to be addressed in this WL +====================================== +The problem actually consists of two parts: +1. Condition on VIEW columns are not pushed down into VIEWs. +2. Even if conditions were pushed, they would have been put into VIEW's +HAVING clause, which would not give enough of speedup. In order to get a +real speedup, the optimizer must be able to move relevant part of HAVING +into WHERE (and then use it for further optimizations) in order to provide +the desired speedup. Note that HAVING->WHERE condition move is orthogonal +to VIEW processing. + +2. Pushdown of conditions into non-mergeable VIEWs +================================================== +We can push a condition into non-mergeable VIEW when VIEW's top-most operation +is selection (i.e., filtering). This is true, for example, when the VIEW is +defined as + + SELECT select_list FROM from_clause [WHERE where_cond] [HAVING having_cond] + +and not true when the VIEW is defined as + + SELECT select_list FROM from_clause [WHERE where_cond] ORDER BY expr LIMIT n + +Generalizing the above, we arrive at the following rule: + + For non-mergeable VIEWs, + - pushdown must not be done if VIEW uses ORDER BY .. LIMIT + - when pushdown is done, the pushed condition should be added to the WHERE + clause. + +Note: In scope of this WL, we will not hande VIEWs that have UNION [ALL] as +top operation. + +(TODO: what about SELECT DISTINCT?) +(TODO: pushdown down into IN subqueries?) + +2.1 A note about VIEWs with ORDER BY ... LIMIT +---------------------------------------------- +Although it is not possible to push a condition below the ORDER BY ... LIMIT +operation, there is still some benefit from checking the condition early as +that would allow to avoid writing non-matching rows into temporary table. + +We could do that if we introduced a post-ORDERBY selection operation. That +operation would also allow to support ORDER BY ... LIMIT inside subqueries +(we don't currently support those because default subquery strategy, +IN->EXISTS rewrite, also needs to push a condition into subquery). + +2.2 What condition can be pushed +-------------------------------- +Assuming simplify_joins() operation has done normalization: +* If the VIEW is in top-level join list, or inside a semi-join that's in + top-level join list, we can push parts of WHERE condition. +* If the VIEW is inside an outer join, we can push it's ON expression. + +We can reuse make_cond_for_index()/make_remainder_cond() code to extract part +of condition that can be pushed, and the remainder, respectively. + +Pushability criteria for an atomic (i.e. not AND/OR) condition is that + + the condition only uses VIEW's fields. + +(TODO: what about fields of const tables? Do we have const tables already +retrived by the time VIEW is materialized? If yes, we could push down +expressions that refer to const tables, too) + +3. Pushdown from HAVING into WHERE +================================== +The idea is: + + Parts of HAVING that refer to columns/expressions we're doing GROUP BY on + can be put into WHERE. + +(TODO: do we need to handle case of grouping over expressions?) + +(TODO: when moving expression for HAVING to WHERE, do we need +to do something with it? Replace all Item_ref objects with items that +they refer to? + - In case of referring to expression, do we get + Item_ref(where_clause_expr) or expr( Item_ref(..), .., Item_ref(..))? +) + +4. When to do the pushdown +========================== +In order to do pushdown, we must have prepare phase finished +for both parent (so that we can make sense of its WHERE condition) and +child (so that we know what it has in its select list). + +We can do pushdown before we've done join optimization (i.e. choose_plan() +call) of the parent. + +We must do pushdown before we've done JOIN::optimize() of the child +(in particular, it must be done before we do update_ref_and_keys() and +range analysis in the child). + + +5. Other things to take care of +=============================== +* Pushing down fulltext predicates (it seems one needs to "register" a + fulltext predicate when it is moved from one select from another? Ask Serg) DESCRIPTION: There are complaints (see links below) about cases with non-mergeable VIEW (because it has a GROUP BY), a query that has restrictions on the grouped column, and poor performance that is caused by VIEW processing code ignoring the restriction. This WL is about addressing this issue. links to complaints: http://code.openark.org/blog/mysql/views-better-performance-with-condition-… http://www.mysqlperformanceblog.com/2010/05/19/a-workaround-for-the-perform… The target version is MariaDB 5.3+, because it has late optimization/execution for FROM-subqueries/non mergeable VIEWs, which makes it much more feasible to inject something into VIEW before it is optimized/executed. HIGH-LEVEL SPECIFICATION: <contents> HLS 1. Problems to be addressed in this WL 2. Pushdown of conditions into non-mergeable VIEWs 2.1 A note about VIEWs with ORDER BY ... LIMIT 2.2 What condition can be pushed 3. Pushdown from HAVING into WHERE 4. When to do the pushdown 5. Other things to take care of </contents> 1. Problems to be addressed in this WL ====================================== The problem actually consists of two parts: 1. Condition on VIEW columns are not pushed down into VIEWs. 2. Even if conditions were pushed, they would have been put into VIEW's HAVING clause, which would not give enough of speedup. In order to get a real speedup, the optimizer must be able to move relevant part of HAVING into WHERE (and then use it for further optimizations) in order to provide the desired speedup. Note that HAVING->WHERE condition move is orthogonal to VIEW processing. 2. Pushdown of conditions into non-mergeable VIEWs ================================================== We can push a condition into non-mergeable VIEW when VIEW's top-most operation is selection (i.e., filtering). This is true, for example, when the VIEW is defined as SELECT select_list FROM from_clause [WHERE where_cond] [HAVING having_cond] and not true when the VIEW is defined as SELECT select_list FROM from_clause [WHERE where_cond] ORDER BY expr LIMIT n Generalizing the above, we arrive at the following rule: For non-mergeable VIEWs, - pushdown must not be done if VIEW uses ORDER BY .. LIMIT - when pushdown is done, the pushed condition should be added to the WHERE clause. Note: In scope of this WL, we will not hande VIEWs that have UNION [ALL] as top operation. (TODO: what about SELECT DISTINCT?) (TODO: pushdown down into IN subqueries?) 2.1 A note about VIEWs with ORDER BY ... LIMIT ---------------------------------------------- Although it is not possible to push a condition below the ORDER BY ... LIMIT operation, there is still some benefit from checking the condition early as that would allow to avoid writing non-matching rows into temporary table. We could do that if we introduced a post-ORDERBY selection operation. That operation would also allow to support ORDER BY ... LIMIT inside subqueries (we don't currently support those because default subquery strategy, IN->EXISTS rewrite, also needs to push a condition into subquery). 2.2 What condition can be pushed -------------------------------- Assuming simplify_joins() operation has done normalization: * If the VIEW is in top-level join list, or inside a semi-join that's in top-level join list, we can push parts of WHERE condition. * If the VIEW is inside an outer join, we can push it's ON expression. We can reuse make_cond_for_index()/make_remainder_cond() code to extract part of condition that can be pushed, and the remainder, respectively. Pushability criteria for an atomic (i.e. not AND/OR) condition is that the condition only uses VIEW's fields. (TODO: what about fields of const tables? Do we have const tables already retrived by the time VIEW is materialized? If yes, we could push down expressions that refer to const tables, too) 3. Pushdown from HAVING into WHERE ================================== The idea is: Parts of HAVING that refer to columns/expressions we're doing GROUP BY on can be put into WHERE. (TODO: do we need to handle case of grouping over expressions?) (TODO: when moving expression for HAVING to WHERE, do we need to do something with it? Replace all Item_ref objects with items that they refer to? - In case of referring to expression, do we get Item_ref(where_clause_expr) or expr( Item_ref(..), .., Item_ref(..))? ) 4. When to do the pushdown ========================== In order to do pushdown, we must have prepare phase finished for both parent (so that we can make sense of its WHERE condition) and child (so that we know what it has in its select list). We can do pushdown before we've done join optimization (i.e. choose_plan() call) of the parent. We must do pushdown before we've done JOIN::optimize() of the child (in particular, it must be done before we do update_ref_and_keys() and range analysis in the child). 5. Other things to take care of =============================== * Pushing down fulltext predicates (it seems one needs to "register" a fulltext predicate when it is moved from one select from another? Ask Serg) ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

1 0

[Maria-developers] New (by Psergey): Push conditions down into non-mergeable VIEWs when possible (119)
by worklog-noreply＠askmonty.org 24 May '10

24 May '10

----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- TASK...........: Push conditions down into non-mergeable VIEWs when possible CREATION DATE..: Mon, 24 May 2010, 20:52 SUPERVISOR.....: Igor IMPLEMENTOR....: COPIES TO......: Psergey, Timour CATEGORY.......: Server-RawIdeaBin TASK ID........: 119 (http://askmonty.org/worklog/?tid=119) VERSION........: Server-9.x STATUS.........: Un-Assigned PRIORITY.......: 60 WORKED HOURS...: 0 ESTIMATE.......: 0 (hours remain) ORIG. ESTIMATE.: 0 PROGRESS NOTES: DESCRIPTION: There are complaints (see links below) about cases with non-mergeable VIEW (because it has a GROUP BY), a query that has restrictions on the grouped column, and poor performance that is caused by VIEW processing code ignoring the restriction. This WL is about addressing this issue. links to complaints: http://code.openark.org/blog/mysql/views-better-performance-with-condition-… http://www.mysqlperformanceblog.com/2010/05/19/a-workaround-for-the-perform… The target version is MariaDB 5.3+, because it has late optimization/execution for FROM-subqueries/non mergeable VIEWs, which makes it much more feasible to inject something into VIEW before it is optimized/executed. ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)

1 0