March 2020 - developers - lists.mariadb.org

Re: [Maria-developers] ef2519fee4e: MDEV-16546 System versioning setting to allow history modification
by Aleksey Midenkov 08 Jun '21

08 Jun '21

Hello, Sergei! On Fri, May 3, 2019 at 8:43 PM Sergei Golubchik <serg(a)mariadb.com> wrote: > > Hi, Aleksey! > > On May 03, Aleksey Midenkov wrote: > > revision-id: ef2519fee4e (versioning-1.0.5-17-gef2519fee4e) > > parent(s): 56145be2951 > > author: Aleksey Midenkov <midenok(a)gmail.com> > > committer: Aleksey Midenkov <midenok(a)gmail.com> > > timestamp: 2018-06-28 13:42:09 +0300 > > message: > > > > MDEV-16546 System versioning setting to allow history modification > > > > 1. Add server variable system_versioning_modify_history which will > > allow to set values for row_start, row_end in DML operations. > > > > 2. If secure_timestamp is YES or REPLICATION, > > system_versioning_modify_history does not have effect. If > > secure_timestamp is SUPER, system_versioning_modify_history requires > > special privilege (same as for setting current timestamp). > > I thought more about this idea. We don't really want to have the history > editable, do we? Well, I'm thinking about rollback table data to specific point in time. That could be a useful feature. > But it's needed for replication, to keep the master and > slave identical. That's what secure_timestamp is for. > > The idea was that this new variable, system_versioning_modify_history, > will be just a convenience feature, it will not allow history editing > any more than one can do without it. > > But now I suspect that even with secure_timestamp=NO one cannot truly > edit history. One can only insert new rows with arbitrary timestamps. > For example, to insert a row with row_start=1000 and row_end=2000, one > needs to do (if secure_timestamp=NO): > > set timestamp=1000; > insert row; > set timestamp=2000; > delete row; > > But I don't see how one can update or delete a history row with > secure_timestamp=NO. > > Now, with a SUPER privilege and secure_timestamp=NO or SUPER, one can > use the BINLOG command and truly edit the history arbitrarily, by faking > row events. I don't really get it why this is so important: since there is some limitation by configuration and privilege, we are just fine. Everything can be changed at filesystem level after all. > > The conclusion, I believe, is that system_versioning_modify_history > should allow INSERTs when secure_timestamp=NO, and it should allow > UPDATE/DELETE only for a SUPER user when secure_timestamp=NO or SUPER. I don't see a reason to argue on that. The only thing that is not clear, why we don't allow INSERTs when secure_timestamp=SUPER? > > The second thing I don't like at all, is when a table is created like > > CREATE TABLE t1 (a int) WITH SYSTEM VERSIONING > > with row_start/row_end implicit. You don't have it in the test, but > anyway one should be able to load history into such a table, while the > table does not have row_start and row_end columns. From the user point > of view these columns don't exist, they're pseudo-columns, like ROWID. > They just cannot be insertable-into, conceptually. But a user will want > to restore the history, right? I don't have a solution for this yet :( > Any ideas? We don't have to follow the conception if it doesn't help us. Since we have physical row_start/row_end, we don't have to pretend they don't exist. Who will win from that? > > See below a couple of minor comments about the patch itself. > > ... These are going to be fixed. > > Regards, > Sergei > Chief Architect MariaDB > and security(a)mariadb.org -- All the best, Aleksey Midenkov @midenok

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Re: [Maria-developers] 7b03ce7af3d: MDEV-17395 REPLACE/INSERT ODKU: support WITHOUT OVERLAPS
by Sergei Golubchik 06 Apr '20

06 Apr '20

Hi, Nikita! First, about tests: On Mar 06, Nikita Malyavin wrote: > revision-id: 7b03ce7af3d (mariadb-10.4.4-504-g7b03ce7af3d) > parent(s): 5c94cf3bf44 > author: Nikita Malyavin <nikitamalyavin(a)gmail.com> > committer: Nikita Malyavin <nikitamalyavin(a)gmail.com> > timestamp: 2019-11-28 01:38:53 +1000 > message: > > MDEV-17395 REPLACE/INSERT ODKU: support WITHOUT OVERLAPS > > --- > mysql-test/suite/period/r/insert_replace.result | 56 +++ > mysql-test/suite/period/t/insert_replace.test | 37 ++ > sql/handler.cc | 14 + > sql/handler.h | 3 +- > sql/sql_insert.cc | 492 ++++++++++++++---------- > sql/sql_load.cc | 6 + > sql/table.cc | 4 +- > sql/table.h | 5 +- > 8 files changed, 409 insertions(+), 208 deletions(-) > > diff --git a/mysql-test/suite/period/r/insert_replace.result b/mysql-test/suite/period/r/insert_replace.result > --- /dev/null > +++ b/mysql-test/suite/period/r/insert_replace.result > @@ -0,0 +1,56 @@ > +create or replace table t(id int, val int, s date, e date, > +period for p(s,e), > +primary key(id, p without overlaps)) engine=myisam; > +insert into t values (1, 1, '2003-01-01', '2003-03-01'), > +(1, 2, '2003-05-01', '2003-07-01'); > +# This just inserts a row; no rows matched > +insert into t values (2, 3, '2003-01-01', '2003-04-01') > +on duplicate key update val=3; > +# The following command is equivalent to > +# MERGE INTO t USING t > +# ON id = 1 AND s <= 2003-04-01 AND e > 2003-01-01 > +# WHEN MATCHED UPDATE SET val=3 > +# WHEN NOT MATCHED INSERT VALUES (1, 3, '2003-01-01', '2003-04-01'); > +insert into t values (1, 3, '2003-01-01', '2003-04-01') > +on duplicate key update val=3; > +select row_count(); > +row_count() > +2 > +select * from t; > +id val s e > +1 3 2003-01-01 2003-03-01 > +1 2 2003-05-01 2003-07-01 > +2 3 2003-01-01 2003-04-01 It's somewhat misleading, because you've used '3' everywhere. Please rewrite your tests (all of them, also tests below) to identify every operation uniquely. For example: insert into t values (1, 1, '2003-01-01', '2003-03-01'), (1, 2, '2003-05-01', '2003-07-01'); # This just inserts a row; no rows matched insert into t values (2, 3, '2003-01-01', '2003-04-01') on duplicate key update val=4; # The following command is equivalent to # MERGE INTO t USING t # ON id = 1 AND s <= 2003-04-01 AND e > 2003-01-01 # WHEN MATCHED UPDATE SET val=6 # WHEN NOT MATCHED INSERT VALUES (1, 5, '2003-01-01', '2003-04-01'); insert into t values (1, 5, '2003-01-01', '2003-04-01') on duplicate key update val=6; > +insert into t values (1, 3, '2003-01-01', '2003-06-01') > +on duplicate key update val=4; > +select row_count(); > +row_count() > +4 > +select * from t; > +id val s e > +1 4 2003-01-01 2003-03-01 > +1 4 2003-05-01 2003-07-01 > +2 3 2003-01-01 2003-04-01 I don't think IODKU is defined via MERGE. Unfortunately. See, how it works: create table t1 (a int not null, b int not null, c int, unique(a), unique(b)); insert t1 values (1,1,1), (2,2,2); insert t1 values (1,2,3) on duplicate key update c=4; select * from t1; a b c 1 1 4 2 2 2 here only one row was updated. If it would've been defined as MERGE INTO t1 USING t1 ON a=1 OR b=2 WHEN MATCHED UPDATE c=4 WHEN NOT MATCHED INSERT VALUES (1,2,3) then it would've updated both rows. As you can see it literally is defined as "insert, and if there's a duplicate key error, then update the conflicting row instead" That is, in your case it should've updated only one row too. Also, please, add this statement to your test: insert into t values (1, 3, '2003-01-01', '2003-02-01') on duplicate key update val=4; > +# No rows matched > +insert into t values (1, 3, '2003-07-01', '2003-08-01') > +on duplicate key update val=5; > +select row_count(); > +row_count() > +1 > +select * from t; > +id val s e > +1 4 2003-01-01 2003-03-01 > +1 4 2003-05-01 2003-07-01 > +2 3 2003-01-01 2003-04-01 > +1 3 2003-07-01 2003-08-01 > +replace into t values(1, 6, '2003-01-01', '2003-06-01'); > +select row_count(); > +row_count() > +4 > +select * from t; > +id val s e > +1 6 2003-01-01 2003-06-01 > +1 4 2003-06-01 2003-07-01 > +2 3 2003-01-01 2003-04-01 > +1 3 2003-07-01 2003-08-01 Here you do DELETE FOR PERIOD. But above you didn't do UPDATE FOR PERIOD. Add also this: replace into t values(1, 6, '2003-01-01', '2003-02-01'); And tests for INSERT SELECT (also with IGNORE, REPLACE, ODKU) and for LOAD DATA (also with IGNORE and REPLACE). > +drop table t; Now, about semantics. It is very arguable here. One options is to do, literally, "insert, if fails delete/update the conflicting row". No periods involved here. The other option is to use FOR PERIOD implicitly for updates and deletes. Example, in all test cases below I'll assume: insert t1 values (1,1,'2003-01-01','2003-03-01'); insert t1 values (1,2,'2003-05-01','2003-06-01'); -> 1 1 2003-01-01 2003-03-01 1 2 2003-05-01 2003-06-01 So, option one: insert t1 values (1,3,'2003-01-01','2003-02-01') on duplicate key update val=4; -> 1 4 2003-01-01 2003-02-01 1 2 2003-05-01 2003-06-01 Option two: insert t1 values (1,3,'2003-01-01','2003-02-01') on duplicate key update val=4; -> 1 4 2003-01-01 2003-02-01 1 1 2003-02-01 2003-03-01 1 2 2003-05-01 2003-06-01 Overlapping range, option two: insert t1 values (1,3,'2003-01-01','2003-04-01') on duplicate key update val=4; -> 1 4 2003-01-01 2003-03-01 1 3 2003-03-01 2003-04-01 1 2 2003-05-01 2003-06-01 And the same for replace, basically: replace t1 values (1,3,'2003-01-01','2003-02-01'); -> 1 3 2003-01-01 2003-02-01 1 2 2003-05-01 2003-06-01 or -> 1 3 2003-01-01 2003-02-01 1 1 2003-02-01 2003-03-01 1 2 2003-05-01 2003-06-01 Regards, Sergei VP of MariaDB Server Engineering and security(a)mariadb.org

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Re: [Maria-developers] 46c66698d63: MENT-566 jUnit xml fixes
by Sergei Golubchik 01 Apr '20

01 Apr '20

Hi, Rasmus! Please, see below On Mar 30, Rasmus Johansson wrote: > revision-id: 46c66698d63 (mariadb-10.2.31-189-g46c66698d63) > parent(s): 065a3d3eed7 > author: Rasmus Johansson <razze(a)iki.fi> > committer: Rasmus Johansson <razze(a)iki.fi> > timestamp: 2020-03-26 10:50:06 +0000 > message: > > MENT-566 jUnit xml fixes > > diff --git a/mysql-test/lib/mtr_report.pm b/mysql-test/lib/mtr_report.pm > index 3701ad79b15..1c6825d8fb7 100644 > --- a/mysql-test/lib/mtr_report.pm > +++ b/mysql-test/lib/mtr_report.pm > @@ -35,6 +37,7 @@ use My::Platform; > use POSIX qw[ _exit ]; > use IO::Handle qw[ flush ]; > use mtr_results; > +use Cwd 'abs_path'; this seems to be unused now > > use Term::ANSIColor; > > @@ -60,6 +63,8 @@ our $verbose; > our $verbose_restart= 0; > our $timer= 1; > > +my $xml_report = ""; this could be moved down inside if ($::opt_xml_report) > + > sub report_option { > my ($opt, $value)= @_; > > @@ -402,6 +409,92 @@ sub mtr_report_stats ($$$$) { > print "All $tot_tests tests were successful.\n\n"; > } > > + if ($::opt_xml_report) { > + my @sorted_tests = sort {$a->{'name'} cmp $b->{'name'}} @$tests; > + my $last_suite = ""; > + my $current_suite = ""; > + my $timest = isotime(time); > + my %suite_totals; > + my %suite_time; > + my %suite_tests; > + my %suite_failed; > + my %suite_disabled; > + my %suite_skipped; > + my $host = hostname; > + my $suiteNo = 0; > + > + # loop through test results to count totals > + foreach my $test ( @sorted_tests ) { > + $current_suite = $test->{'suite'}->{'name'}; > + > + if ($test->{'timer'} eq "") { > + $test->{'timer'} = 0; > + } > + > + # $suite_totals{$current_suite . "_time"} = $suite_totals{$current_suite . "_time"} + $test->{'timer'}; > + # $suite_totals{$current_suite . "_tests"} = $suite_totals{$current_suite . "_tests"} + 1; don't forget to remove all these commented-out lines before pushing > + $suite_time{$current_suite} = $suite_time{$current_suite} + $test->{'timer'}; > + $suite_tests{$current_suite} = $suite_tests{$current_suite} + 1; > + > + if ($test->{'result'} eq "MTR_RES_FAILED") { > + # $suite_totals{$current_suite . "_failed"} = $suite_totals{$current_suite . "_failed"} + 1; > + $suite_failed{$current_suite} = $suite_failed{$current_suite} + 1; > + } elsif ($test->{'result'} eq "MTR_RES_SKIPPED" && $test->{'disable'}) { > + # $suite_totals{$current_suite . "_disabled"} = $suite_totals{$current_suite . "_disabled"} + 1; > + $suite_disabled{$current_suite} = $suite_disabled{$current_suite} + 1; > + } elsif ($test->{'result'} eq "MTR_RES_SKIPPED") { > + $suite_skipped{$current_suite} = $suite_skipped{$current_suite} + 1; > + } > + > + $suite_totals{"all_time"} = $suite_totals{"all_time"} + $test->{'timer'}; > + } > + > + # generate xml > + $xml_report = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"; > + $xml_report = $xml_report . "<testsuites disabled=\"" . $tot_disabled . "\" errors=\"\" failures=\"" . $tot_failed . "\" name=\"\" tests=\"" . $tot_tests . "\" time=\"" . $suite_totals{"all_time"} . "\">\n"; I find it more concise to write $xml_report .= "<testsuites ..." instead of $xml_report = $xml_report . "<testsuites ..." and also it's easier to read, because the first form directly means "append to the variable", while the second means "concatenate two strings and store the result" and by using the target variable also as first string one gets the append effect. > + > + foreach my $test ( @sorted_tests ) { > + $current_suite = $test->{'suite'}->{'name'}; > + > + if ($current_suite ne $last_suite) { > + if ($last_suite ne "") { > + $xml_report = $xml_report . "\t</testsuite>\n"; > + $suiteNo++; > + } > + > + $xml_report = $xml_report . "\t<testsuite disabled=\"" . $suite_disabled{$current_suite} . "\" errors=\"\" failures=\"" . $suite_failed{$current_suite} . "\" hostname=\"" . $host . "\" id=\"" . $suiteNo . "\" name=\"" . $current_suite . "\" package=\"\" skipped=\"" . $suite_skipped{$current_suite} . "\" tests=\"" . $suite_tests{$current_suite} . "\" time=\"" . $suite_time{$current_suite} . "\" timestamp=\"" . $timest . "\">\n"; why do you always avoid variable interapolation? The above line could've been written as $xml_report .= qq(\t<testsuite disabled="$suite_disabled{$current_suite}" errors="" failures="$suite_failed{$current_suite}" hostname="$host" id="$suiteNo" name="$current_suite" package="" skipped="$suite_skipped{$current_suite}" tests="$suite_tests{$current_suite}" time="$suite_time{$current_suite}" timestamp="$timest">\n); which is notably shorter and more readable > + $last_suite = $current_suite; > + } > + > + $xml_report = $xml_report . "\t\t<testcase assertions=\"\" classname=\"" . $current_suite . "\" name=\"$test->{'name'}\" status=\"$test->{'result'}\" time=\"" . $test->{timer} . "\""; > + > + if ($test->{'result'} eq "MTR_RES_FAILED") { > + $xml_report = $xml_report . ">\n\t\t\t<failure message=\"\" type=\"" . $test->{'result'} . "\">\n<![CDATA[" . $test->{'logfile'} . "]]>\n\t\t\t</failure>\n\t\t</testcase>\n"; > + } elsif ($test->{'result'} eq "MTR_RES_SKIPPED" && $test->{'disable'}) { > + $xml_report = $xml_report . ">\n\t\t\t<failure message=\"disabled\" type=\"" . $test->{'result'} . "\"/>\n\t\t</testcase>\n"; > + } elsif ($test->{'result'} eq "MTR_RES_SKIPPED") { > + $xml_report = $xml_report . ">\n\t\t\t<failure message=\"skipped\" type=\"" . $test->{'result'} . "\"/>\n\t\t</testcase>\n"; > + } else { > + $xml_report = $xml_report . " />\n"; > + } > + > + # check if last test > + if ($test eq @sorted_tests[$#sorted_tests]) { > + $xml_report = $xml_report . "\t</testsuite>\n"; > + } better to print this after the loop, then to do a check for every test. it will not be wrong, because your condition $test eq @sorted_tests[$#sorted_tests] can only be true once, for the very last test. So you can as well remove the whole if() and put the unconditional $xml_report .= "\t</testsuite>\n"; after the loop. > + } > + > + $xml_report = $xml_report . "</testsuites>\n"; or just combine it with this one: $xml_report .= "\t</testsuite>\n</testsuites>\n"; > + > + # save to file > + # my $xml_file = $::opt_vardir . "/log/" . $::opt_xml_report; > + my $xml_file = $::opt_xml_report; > + > + open XML_FILE, ">" . $xml_file; error checking? Even if it's just open XML_FILE, ">" , $xml_file or die "$!"; and always use the 3-form open(). Where ">" is a separate argument, not concatenated to the file name (see how I wrote it above) > + print XML_FILE $xml_report; > + close XML_FILE; > + } > + > if (@$extra_warnings) > { > print <<MSG; > diff --git a/mysql-test/mysql-test-run.pl b/mysql-test/mysql-test-run.pl > index ef37cb4144d..298ba0015a3 100755 > --- a/mysql-test/mysql-test-run.pl > +++ b/mysql-test/mysql-test-run.pl > @@ -80,6 +80,7 @@ use lib "lib"; > > use Cwd ; > use Cwd 'realpath'; > +use Cwd 'abs_path'; this seems to be unused now > use Getopt::Long; > use My::File::Path; # Patched version of File::Path > use File::Basename; Regards, Sergei VP of MariaDB Server Engineering and security(a)mariadb.org

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Re: [Maria-developers] 7740cb24572: Don't use plugin->data for storage engine plugins
by Sergei Golubchik 31 Mar '20

31 Mar '20

Hi, Sergey! On Mar 31, Sergey Vojtovich wrote: > revision-id: 7740cb24572 (mariadb-10.4.4-472-g7740cb24572) > parent(s): da6d7f72b0a > author: Sergey Vojtovich <svoj(a)mariadb.org> > committer: Sergey Vojtovich <svoj(a)mariadb.org> > timestamp: 2019-11-15 15:23:42 +0400 > message: > > Don't use plugin->data for storage engine plugins > > Use plugin->plugin->info->hton instead. > plugin_data() replaced with plugin_hton(). > plugin_hton() must never return NULL anymore and is only good to be called > against plugins in PLUGIN_IS_READY state. Why is that? Regards, Sergei VP of MariaDB Server Engineering and security(a)mariadb.org

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[Maria-developers] GSOC 2020 - MDEV-11263 Aggregate Window Functions
by Tavneet Sarna 30 Mar '20

30 Mar '20

Hi everyone, As part of GSOC 2020, this is one of the two projects I am interested in pursuing. As guided by last years' comments by Varun and Vicențiu, I have set up a debugger and corresponding breakpoints in the Item_sum_sum::add and Item_sum_sp::add for a custom sum aggregate function to understand the code flow. I had a couple of queries regarding the same: 1. In *do_add *from decimal.c, there are three parts with comments - /* part 1 - MY_MAX(frac) ... min (frac) */, /* part 2 - MY_MIN(frac) ... MY_MIN(intg) */. Can someone please elaborate on what do the comments mean ? 2. In *Item_sum_sum::add_helper*, there is an unlikely branch for variable direct_added. Can someone please give an idea about when will direct added be true ? In fact in all the uses for direct_added, it is always in an unlikely branch in Item_sum.cc. Regards Tavneet

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[Maria-developers] Guidance regarding GSoC Projects.
by Arhant Jain 27 Mar '20

27 Mar '20

Hello Everyone, I'm interested in the work associated with these projects. I tried to explore them on my level. It will be very helpful if the concerned developers can direct some more information regarding these projects. 1. Switching off/on separate tests in mysql-test-run suite 2. Add a bitmap for NULL/empty data 3. Speed up RowGroup data access methods reducing level of indirection Thanks Arhant

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[Maria-developers] Regarding GSoc :ADD FULL OUTER JOIN
by Jeeukrishnan Kayshyap. 26 Mar '20

26 Mar '20

Hi ,I am a GSoC aspirant . I am trying to solve https://jira.mariadb.org/browse/MDEV-13648 . Firstly , I discussed a new algorithm with Igor Babev sir , but it was wrong as it will create space problem. Now , I am planning to add some code in Sql_yacc.yy : /*full join*/ after the right join where /*full join */ will contain : 1.left join implementation (similar to the implementation of left join in sql_yacc.yy (line no. 11956-11950)) The result table will be in a temporary table ->tab1. 2.Use of right join doing the swapping of table (similar to right join in this part ;(line no. 11992-12030)) the result of this will be stored in another temporary table ->tab2 3.Union all clause: implementation of union all clause to combine tab1 and tab2. So , Oleksandr Byelkin sir replied to me that , addition of UNION will make it more complicated.it could be done with less effort than adding full UNION. But at present I am not able to get any idea how to reduce the complexity or any kind of new idea to implement it . Please guide me in the right direction and help me to solve this issue.

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Re: [Maria-developers] fc90a39426c: MDEV-20604: Duplicate key value is silently truncated to 64 characters in print_keydup_error
by Sergei Golubchik 25 Mar '20

25 Mar '20

Hi, Oleksandr! Looks good. Thanks for tests. Ok to push. One comment, see below. On Mar 25, Oleksandr Byelkin wrote: > revision-id: fc90a39426c (mariadb-10.2.31-87-gfc90a39426c) > parent(s): fb74de97287 > author: Oleksandr Byelkin <sanja(a)mariadb.com> > committer: Oleksandr Byelkin <sanja(a)mariadb.com> > timestamp: 2020-03-24 10:34:14 +0100 > message: > > MDEV-20604: Duplicate key value is silently truncated to 64 characters in print_keydup_error > > Added indication of truncated string for "s" and "M" formats > > diff --git a/unittest/mysys/my_vsnprintf-t.c b/unittest/mysys/my_vsnprintf-t.c > index 6ba0a42cf7e..872e88ddd7e 100644 > --- a/unittest/mysys/my_vsnprintf-t.c > +++ b/unittest/mysys/my_vsnprintf-t.c > @@ -168,14 +184,14 @@ int main(void) > test1("M with positional: 0 \"Internal error/check (Not system error)\"", > "M with positional: %1$M", 0); > > - test1("M with width: 0 \"Internal error/ch", > + test1("M with width: 0 \"Internal error...", > "M with width: %.20M", 0); > - test1("M with width positional: 0 \"Internal error/ch", > + test1("M with width positional: 0 \"Internal error...", > "M with width positional: %2$.*1$M", 20, 0); > > - test_w_len("M small buf: 0 \"In", > + test_w_len("M small buf: 0 \"..", > 19, "M small buf: %M", 0); > - test_w_len("M small buf positional: 0 \"In", > + test_w_len("M small buf positional: 0 \"..", > 30, "M small buf positional: %1$M", 0); > > return exit_status(); We didn't discuss truncation when the buffer is too small, only truncation by width. It's not at all clear why truncation by small buffer should also use ellipsis. But it's not clear that it shouldn't either. I don't have a strong opinion in favor of either, so feel free to keep it your way. Regards, Sergei VP of MariaDB Server Engineering and security(a)mariadb.org

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[Maria-developers] GSOC 2020 - MDEV-383
by Tavneet Sarna 25 Mar '20

25 Mar '20

Hi, I was looking into MDEV-383 <https://jira.mariadb.org/browse/MDEV-383> - "*Evaluate subquery predicates earlier or later depending on their SELECTIVITY*" as a possible GSOC 2020 project and I have a few queries about the same. 1. "There are a lot of subquery conditions out there that are inexpensive to evaluate and have good selectivity." - How is the cost of a subquery predicate calculated ? 2. One of the assumptions in MDEV-83 <https://jira.mariadb.org/browse/MDEV-83> was that "selectivity of a subquery predicate cannot be estimated during optimization." - what has changed since that we are looking into estimating selectivity ( or maybe my understanding of the task is incorrect so I would be grateful if you could just point me to any resources regarding this). 3. Igor had responded on the jira - "for starters, you could introduce an option that would allow not to push correlated subquery predicates to joined tables." - did you mean a command line argument/option and I don't get how this would help with the main task. 4. Also, can anyone please point me to the classes where predicate cost and join plans are evaluated ? Apologies if the queries are a bit rudimentary. Regards Tavneet

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[Maria-developers] Regarding GSoc :ADD FULL OUTER JOIN
by Jeeukrishnan Kayshyap. 24 Mar '20

24 Mar '20

HI , to implement FULL OUTER JOIN between T1 and T2 can we do "T1 Left Outer Join T2 union all T2 Anti Join T1" ?? Is this method already tried ? Please guide me to solve this issue and if possible someone please reply to my last email.

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