revision-id: 39570001084ad06556a660dcee6ad951955436e2 (mariadb-10.7.1-3-g39570001084) parent(s): 06988bdcaa2d1af2c178c199b7f65dbafda45a2c author: Sergei Petrunia committer: Sergei Petrunia timestamp: 2022-03-07 20:33:33 +0300 message: MDEV-27188: Suppress optimizer output when executing prepare - Do not write anything into Optimizer Trace at Prepare phase - When the query gets an error at Prepare phase, make sure there is no trace written, either. This is important as we need to produce the same trace for "mtr --ps-protocol" and regular mtr run. - For other kinds of errors, trace is still produced as it might be valuable. (variant 3) --- mysql-test/main/opt_trace,ps.rdiff | 92 --- mysql-test/main/opt_trace.result | 621 +++------------------ mysql-test/main/opt_trace_index_merge.result | 11 +- .../main/opt_trace_index_merge_innodb.result | 11 +- mysql-test/main/opt_trace_security.result | 38 +- sql/my_json_writer.h | 8 + sql/opt_subselect.cc | 13 +- sql/opt_trace.cc | 60 ++ sql/opt_trace.h | 38 +- sql/opt_trace_context.h | 6 + sql/sql_derived.cc | 30 +- sql/sql_parse.cc | 4 + sql/sql_prepare.cc | 11 - sql/sql_select.cc | 17 +- 14 files changed, 236 insertions(+), 724 deletions(-) diff --git a/mysql-test/main/opt_trace,ps.rdiff b/mysql-test/main/opt_trace,ps.rdiff deleted file mode 100644 index 3e2218de673..00000000000 --- a/mysql-test/main/opt_trace,ps.rdiff +++ /dev/null @@ -1,92 +0,0 @@ ---- /Users/shulga/projects/mariadb/server-10.6/mysql-test/main/opt_trace.result 2021-07-21 19:17:11.000000000 +0700 -+++ /Users/shulga/projects/mariadb/server-10.6/mysql-test/main/opt_trace.reject 2021-07-21 19:17:48.000000000 +0700 -@@ -2829,14 +2829,6 @@ - } - }, - { -- "transformation": { -- "select_id": 2, -- "from": "IN (SELECT)", -- "to": "semijoin", -- "chosen": true -- } -- }, -- { - "expanded_query": "/* select#2 */ select t10.pk from t10" - } - ] -@@ -4402,14 +4394,6 @@ - } - }, - { -- "transformation": { -- "select_id": 2, -- "from": "IN (SELECT)", -- "to": "semijoin", -- "chosen": true -- } -- }, -- { - "expanded_query": "/* select#2 */ select t_inner_1.a from t1 t_inner_1 join t1 t_inner_2" - } - ] -@@ -4852,14 +4836,6 @@ - } - }, - { -- "transformation": { -- "select_id": 2, -- "from": "IN (SELECT)", -- "to": "semijoin", -- "chosen": true -- } -- }, -- { - "expanded_query": "/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1" - } - ] -@@ -4879,14 +4855,6 @@ - } - }, - { -- "transformation": { -- "select_id": 3, -- "from": "IN (SELECT)", -- "to": "semijoin", -- "chosen": true -- } -- }, -- { - "expanded_query": "/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4" - } - ] -@@ -6432,14 +6400,6 @@ - } - }, - { -- "transformation": { -- "select_id": 2, -- "from": "IN (SELECT)", -- "to": "semijoin", -- "chosen": true -- } -- }, -- { - "expanded_query": "/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1" - } - ] -@@ -6459,14 +6419,6 @@ - } - }, - { -- "transformation": { -- "select_id": 3, -- "from": "IN (SELECT)", -- "to": "semijoin", -- "chosen": true -- } -- }, -- { - "expanded_query": "/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4" - } - ] diff --git a/mysql-test/main/opt_trace.result b/mysql-test/main/opt_trace.result index b0c2a9ca4d9..18ef904633b 100644 --- a/mysql-test/main/opt_trace.result +++ b/mysql-test/main/opt_trace.result @@ -38,36 +38,18 @@ QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select * from v1 { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from v1", "steps": [ { "view": { "table": "v1", "select_id": 2, - "algorithm": "merged" + "algorithm": "merged", + "expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1" } }, - { - "join_preparation": { - "select_id": 2, - "steps": [ - { - "expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1" - } - ] - } - }, - { - "expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from v1" - } - ] - } - }, - { - "join_optimization": { - "select_id": 1, - "steps": [ { "condition_processing": { "condition": "WHERE", @@ -189,36 +171,18 @@ QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select * from (select * from t1 where t1.a=1)q { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from (/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1) q", "steps": [ { "derived": { "table": "q", "select_id": 2, - "algorithm": "merged" - } - }, - { - "join_preparation": { - "select_id": 2, - "steps": [ - { - "expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1" - } - ] + "algorithm": "merged", + "expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1" } }, - { - "expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from (/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1) q" - } - ] - } - }, - { - "join_optimization": { - "select_id": 1, - "steps": [ { "condition_processing": { "condition": "WHERE", @@ -340,40 +304,15 @@ select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select * from v2 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "view": { - "table": "v2", - "select_id": 2, - "algorithm": "materialized" - } - }, - { - "join_preparation": { - "select_id": 2, - "steps": [ - { - "expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1 group by t1.b" - } - ] - } - }, - { - "expanded_query": "/* select#1 */ select v2.a AS a,v2.b AS b from v2" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select v2.a AS a,v2.b AS b from v2", "steps": [ { "join_optimization": { "select_id": 2, + "expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1 group by t1.b", "steps": [ { "condition_processing": { @@ -590,36 +529,18 @@ QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from v2 { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select t2.a AS a from v2", "steps": [ { "view": { "table": "v2", "select_id": 2, - "algorithm": "merged" + "algorithm": "merged", + "expanded_query": "/* select#2 */ select t2.a AS a from t2" } }, - { - "join_preparation": { - "select_id": 2, - "steps": [ - { - "expanded_query": "/* select#2 */ select t2.a AS a from t2" - } - ] - } - }, - { - "expanded_query": "/* select#1 */ select t2.a AS a from v2" - } - ] - } - }, - { - "join_optimization": { - "select_id": 1, - "steps": [ { "table_dependencies": [ { @@ -702,40 +623,15 @@ select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from v1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "view": { - "table": "v1", - "select_id": 2, - "algorithm": "materialized" - } - }, - { - "join_preparation": { - "select_id": 2, - "steps": [ - { - "expanded_query": "/* select#2 */ select t1.a AS a from t1 group by t1.b" - } - ] - } - }, - { - "expanded_query": "/* select#1 */ select v1.a AS a from v1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select v1.a AS a from v1", "steps": [ { "join_optimization": { "select_id": 2, + "expanded_query": "/* select#2 */ select t1.a AS a from t1 group by t1.b", "steps": [ { "table_dependencies": [ @@ -911,19 +807,10 @@ select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from t1,t2 where t1.a=t2.b+2 and t2.a= t1.b { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.a AS a,t1.b AS b,t1.c AS c,t2.a AS a,t2.b AS b,t2.c AS c from t1 join t2 where t1.a = t2.b + 2 and t2.a = t1.b" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.a AS a,t1.b AS b,t1.c AS c,t2.a AS a,t2.b AS b,t2.c AS c from t1 join t2 where t1.a = t2.b + 2 and t2.a = t1.b", "steps": [ { "condition_processing": { @@ -1162,19 +1049,10 @@ select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES EXPLAIN SELECT DISTINCT a FROM t1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select distinct t1.a AS a from t1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select distinct t1.a AS a from t1", "steps": [ { "table_dependencies": [ @@ -1327,19 +1205,10 @@ select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES EXPLAIN SELECT MIN(d) FROM t1 where b=2 and c=3 group by a { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select min(t1.d) AS `MIN(d)` from t1 where t1.b = 2 and t1.c = 3 group by t1.a" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select min(t1.d) AS `MIN(d)` from t1 where t1.b = 2 and t1.c = 3 group by t1.a", "steps": [ { "condition_processing": { @@ -1526,19 +1395,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a>=20010104e0 GROUP BY id { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.`id` AS `id`,min(t1.a) AS `MIN(a)`,max(t1.a) AS `MAX(a)` from t1 where t1.a >= 20010104e0 group by t1.`id`" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.`id` AS `id`,min(t1.a) AS `MIN(a)`,max(t1.a) AS `MAX(a)` from t1 where t1.a >= 20010104e0 group by t1.`id`", "steps": [ { "condition_processing": { @@ -1714,19 +1574,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES EXPLAIN SELECT * FROM t1 WHERE a = 20010104e0 GROUP BY id { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.`id` AS `id`,t1.a AS a from t1 where t1.a = 20010104e0 group by t1.`id`" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.`id` AS `id`,t1.a AS a from t1 where t1.a = 20010104e0 group by t1.`id`", "steps": [ { "condition_processing": { @@ -1929,19 +1780,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from t1 where a=1 and b=2 order by c limit 1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.pk AS pk,t1.a AS a,t1.b AS b,t1.c AS c,t1.filler AS filler from t1 where t1.a = 1 and t1.b = 2 order by t1.c limit 1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.pk AS pk,t1.a AS a,t1.b AS b,t1.c AS c,t1.filler AS filler from t1 where t1.a = 1 and t1.b = 2 order by t1.c limit 1", "steps": [ { "condition_processing": { @@ -2305,19 +2147,10 @@ QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select t1.a from t1 left join t2 on t1.a=t2.a { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.a AS a from (t1 left join t2 on(t1.a = t2.a))" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.a AS a from (t1 left join t2 on(t1.a = t2.a))", "steps": [ { "build_equal_items": { @@ -2442,19 +2275,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from t1 left join t2 on t2.a=t1.a { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.a AS a,t2.a AS a,t2.b AS b from (t1 left join t2 on(t2.a = t1.a))" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.a AS a,t2.a AS a,t2.b AS b from (t1 left join t2 on(t2.a = t1.a))", "steps": [ { "build_equal_items": { @@ -2621,19 +2445,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select t1.a from t1 left join (t2 join t3 on t2.b=t3.b) on t2.a=t1.a and t3.a=t1.a { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.a AS a from (t1 left join (t2 join t3 on(t2.b = t3.b)) on(t2.a = t1.a and t3.a = t1.a))" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.a AS a from (t1 left join (t2 join t3 on(t2.b = t3.b)) on(t2.a = t1.a and t3.a = t1.a))", "steps": [ { "build_equal_items": { @@ -2812,46 +2627,19 @@ QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain extended select * from t1 where a in (select pk from t10) { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from t1 where t1.a in (/* select#2 */ select t10.pk from t10)", "steps": [ { - "join_preparation": { + "transformation": { "select_id": 2, - "steps": [ - { - "transformation": { - "select_id": 2, - "from": "IN (SELECT)", - "to": "materialization", - "sjm_scan_allowed": true, - "possible": true - } - }, - { - "transformation": { - "select_id": 2, - "from": "IN (SELECT)", - "to": "semijoin", - "chosen": true - } - }, - { - "expanded_query": "/* select#2 */ select t10.pk from t10" - } - ] + "from": "IN (SELECT)", + "to": "materialization", + "sjm_scan_allowed": true, + "possible": true } }, - { - "expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from t1 where t1.a in (/* select#2 */ select t10.pk from t10)" - } - ] - } - }, - { - "join_optimization": { - "select_id": 1, - "steps": [ { "transformation": { "select_id": 2, @@ -3135,19 +2923,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from t1 where pk = 2 and a=5 and b=1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.pk AS pk,t1.a AS a,t1.b AS b from t1 where t1.pk = 2 and t1.a = 5 and t1.b = 1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.pk AS pk,t1.a AS a,t1.b AS b from t1 where t1.pk = 2 and t1.a = 5 and t1.b = 1", "steps": [ { "condition_processing": { @@ -3496,19 +3275,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select f1(a) from t1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select f1(t1.a) AS `f1(a)` from t1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select f1(t1.a) AS `f1(a)` from t1", "steps": [ { "table_dependencies": [ @@ -3593,19 +3363,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select f2(a) from t1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select f2(t1.a) AS `f2(a)` from t1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select f2(t1.a) AS `f2(a)` from t1", "steps": [ { "table_dependencies": [ @@ -3697,7 +3458,7 @@ a 2 select length(trace) from INFORMATION_SCHEMA.OPTIMIZER_TRACE; length(trace) -2141 +2012 set optimizer_trace_max_mem_size=100; select * from t1; a @@ -3708,10 +3469,9 @@ QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select * from t1 { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, - "steps": [ - 2041 0 + "expanded_query": 1912 0 set optimizer_trace_max_mem_size=0; select * from t1; a @@ -3719,7 +3479,7 @@ a 2 select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES -select * from t1 2141 0 +select * from t1 2012 0 drop table t1; set optimizer_trace='enabled=off'; set @@optimizer_trace_max_mem_size= @save_optimizer_trace_max_mem_size; @@ -3809,19 +3569,10 @@ select * from information_schema.optimizer_trace; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain delete t0,t1 from t0, t1 where t0.a=t1.a and t1.a<3 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select NULL AS `NULL` from t0 join t1 where t0.a = t1.a and t1.a < 3" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select NULL AS `NULL` from t0 join t1 where t0.a = t1.a and t1.a < 3", "steps": [ { "condition_processing": { @@ -4175,36 +3926,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from (select rand() from t1)q { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "derived": { - "table": "q", - "select_id": 2, - "algorithm": "merged" - } - }, - { - "join_preparation": { - "select_id": 2, - "steps": [ - { - "expanded_query": "/* select#2 */ select rand() AS `rand()` from t1" - } - ] - } - }, - { - "expanded_query": "/* select#1 */ select rand() AS `rand()` from (/* select#2 */ select rand() AS `rand()` from t1) q" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select rand() AS `rand()` from (/* select#2 */ select rand() AS `rand()` from t1) q", "steps": [ { "derived": { @@ -4217,6 +3942,7 @@ explain select * from (select rand() from t1)q { { "join_optimization": { "select_id": 2, + "expanded_query": "/* select#2 */ select rand() AS `rand()` from t1", "steps": [ { "table_dependencies": [ @@ -4385,46 +4111,19 @@ QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from t1 where a in (select t_inner_1.a from t1 t_inner_1, t1 t_inner_2) { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select t1.a AS a from t1 where t1.a in (/* select#2 */ select t_inner_1.a from t1 t_inner_1 join t1 t_inner_2)", "steps": [ { - "join_preparation": { + "transformation": { "select_id": 2, - "steps": [ - { - "transformation": { - "select_id": 2, - "from": "IN (SELECT)", - "to": "materialization", - "sjm_scan_allowed": true, - "possible": true - } - }, - { - "transformation": { - "select_id": 2, - "from": "IN (SELECT)", - "to": "semijoin", - "chosen": true - } - }, - { - "expanded_query": "/* select#2 */ select t_inner_1.a from t1 t_inner_1 join t1 t_inner_2" - } - ] + "from": "IN (SELECT)", + "to": "materialization", + "sjm_scan_allowed": true, + "possible": true } }, - { - "expanded_query": "/* select#1 */ select t1.a AS a from t1 where t1.a in (/* select#2 */ select t_inner_1.a from t1 t_inner_1 join t1 t_inner_2)" - } - ] - } - }, - { - "join_optimization": { - "select_id": 1, - "steps": [ { "transformation": { "select_id": 2, @@ -4835,73 +4534,19 @@ explain select * from t1 t_outer_1,t2 t_outer_2 where t_outer_1.a in (select t_ t_outer_2.a in (select t_inner_3.a from t2 t_inner_3, t1 t_inner_4) { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select t_outer_1.a AS a,t_outer_2.a AS a from t1 t_outer_1 join t2 t_outer_2 where t_outer_1.a in (/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1) and t_outer_2.a in (/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4)", "steps": [ { - "join_preparation": { + "transformation": { "select_id": 2, - "steps": [ - { - "transformation": { - "select_id": 2, - "from": "IN (SELECT)", - "to": "materialization", - "sjm_scan_allowed": true, - "possible": true - } - }, - { - "transformation": { - "select_id": 2, - "from": "IN (SELECT)", - "to": "semijoin", - "chosen": true - } - }, - { - "expanded_query": "/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1" - } - ] - } - }, - { - "join_preparation": { - "select_id": 3, - "steps": [ - { - "transformation": { - "select_id": 3, - "from": "IN (SELECT)", - "to": "materialization", - "sjm_scan_allowed": true, - "possible": true - } - }, - { - "transformation": { - "select_id": 3, - "from": "IN (SELECT)", - "to": "semijoin", - "chosen": true - } - }, - { - "expanded_query": "/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4" - } - ] + "from": "IN (SELECT)", + "to": "materialization", + "sjm_scan_allowed": true, + "possible": true } }, - { - "expanded_query": "/* select#1 */ select t_outer_1.a AS a,t_outer_2.a AS a from t1 t_outer_1 join t2 t_outer_2 where t_outer_1.a in (/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1) and t_outer_2.a in (/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4)" - } - ] - } - }, - { - "join_optimization": { - "select_id": 1, - "steps": [ { "transformation": { "select_id": 2, @@ -4910,6 +4555,15 @@ t_outer_2.a in (select t_inner_3.a from t2 t_inner_3, t1 t_inner_4) { "converted_to_semi_join": true } }, + { + "transformation": { + "select_id": 3, + "from": "IN (SELECT)", + "to": "materialization", + "sjm_scan_allowed": true, + "possible": true + } + }, { "transformation": { "select_id": 3, @@ -6415,73 +6069,19 @@ explain select * from t1 t_outer_1,t2 t_outer_2 where t_outer_1.a in (select t_ t_outer_2.a in (select t_inner_3.a from t2 t_inner_3, t1 t_inner_4) { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select t_outer_1.a AS a,t_outer_2.a AS a from t1 t_outer_1 join t2 t_outer_2 where t_outer_1.a in (/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1) and t_outer_2.a in (/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4)", "steps": [ { - "join_preparation": { + "transformation": { "select_id": 2, - "steps": [ - { - "transformation": { - "select_id": 2, - "from": "IN (SELECT)", - "to": "materialization", - "sjm_scan_allowed": true, - "possible": true - } - }, - { - "transformation": { - "select_id": 2, - "from": "IN (SELECT)", - "to": "semijoin", - "chosen": true - } - }, - { - "expanded_query": "/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1" - } - ] - } - }, - { - "join_preparation": { - "select_id": 3, - "steps": [ - { - "transformation": { - "select_id": 3, - "from": "IN (SELECT)", - "to": "materialization", - "sjm_scan_allowed": true, - "possible": true - } - }, - { - "transformation": { - "select_id": 3, - "from": "IN (SELECT)", - "to": "semijoin", - "chosen": true - } - }, - { - "expanded_query": "/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4" - } - ] + "from": "IN (SELECT)", + "to": "materialization", + "sjm_scan_allowed": true, + "possible": true } }, - { - "expanded_query": "/* select#1 */ select t_outer_1.a AS a,t_outer_2.a AS a from t1 t_outer_1 join t2 t_outer_2 where t_outer_1.a in (/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1) and t_outer_2.a in (/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4)" - } - ] - } - }, - { - "join_optimization": { - "select_id": 1, - "steps": [ { "transformation": { "select_id": 2, @@ -6490,6 +6090,15 @@ t_outer_2.a in (select t_inner_3.a from t2 t_inner_3, t1 t_inner_4) { "converted_to_semi_join": true } }, + { + "transformation": { + "select_id": 3, + "from": "IN (SELECT)", + "to": "materialization", + "sjm_scan_allowed": true, + "possible": true + } + }, { "transformation": { "select_id": 3, @@ -8677,19 +8286,10 @@ SELECT query, trace FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE; query trace SELECT 'a\0' LIMIT 0 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select 'a\0' AS `a\x00` limit 0" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select 'a\0' AS `a\x00` limit 0", "steps": [] } }, @@ -8716,19 +8316,10 @@ select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select count(*) from seq_1_to_10000000 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select count(0) AS `count(*)` from seq_1_to_10000000" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select count(0) AS `count(*)` from seq_1_to_10000000", "steps": [ { "table_dependencies": [ @@ -8855,50 +8446,6 @@ json_detailed(json_extract(trace, '$**.in_to_subquery_conversion')) "item": "t0.a in (1,2,3,4,5,6)", "conversion": [ - - { - "join_preparation": - { - "select_id": 2, - "steps": - [ - - { - "derived": - { - "table": "tvc_0", - "select_id": 3, - "algorithm": "materialized" - } - }, - - { - "transformation": - { - "select_id": 2, - "from": "IN (SELECT)", - "to": "materialization", - "sjm_scan_allowed": true, - "possible": true - } - }, - - { - "transformation": - { - "select_id": 2, - "from": "IN (SELECT)", - "to": "semijoin", - "chosen": true - } - }, - - { - "expanded_query": "/* select#2 */ select tvc_0._col_1 from (values (1),(2),(3),(4),(5),(6)) tvc_0" - } - ] - } - } ] } ] @@ -8954,7 +8501,7 @@ set @path= (select json_search(@trace, 'one', 'no predicate for first keypart')) set @sub_path= substr(@path, 2, locate('.best_access_path', @path)-2); select @sub_path; @sub_path -$.steps[1].join_optimization.steps[4].considered_execution_plans[0].rest_of_plan[0] +$.steps[0].join_optimization.steps[4].considered_execution_plans[0].rest_of_plan[0] select json_detailed(json_extract( @trace, diff --git a/mysql-test/main/opt_trace_index_merge.result b/mysql-test/main/opt_trace_index_merge.result index f1e13586eda..b319639e9fa 100644 --- a/mysql-test/main/opt_trace_index_merge.result +++ b/mysql-test/main/opt_trace_index_merge.result @@ -19,19 +19,10 @@ select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from t1 where a=1 or b=1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.a AS a,t1.b AS b,t1.c AS c,t1.filler AS filler from t1 where t1.a = 1 or t1.b = 1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.a AS a,t1.b AS b,t1.c AS c,t1.filler AS filler from t1 where t1.a = 1 or t1.b = 1", "steps": [ { "condition_processing": { diff --git a/mysql-test/main/opt_trace_index_merge_innodb.result b/mysql-test/main/opt_trace_index_merge_innodb.result index 0ddaaeae89d..bc063015e6d 100644 --- a/mysql-test/main/opt_trace_index_merge_innodb.result +++ b/mysql-test/main/opt_trace_index_merge_innodb.result @@ -27,19 +27,10 @@ select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES explain select * from t1 where pk1 != 0 and key1 = 1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select t1.pk1 AS pk1,t1.pk2 AS pk2,t1.key1 AS key1,t1.key2 AS key2 from t1 where t1.pk1 <> 0 and t1.key1 = 1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select t1.pk1 AS pk1,t1.pk2 AS pk2,t1.key1 AS key1,t1.key2 AS key2 from t1 where t1.pk1 <> 0 and t1.key1 = 1", "steps": [ { "condition_processing": { diff --git a/mysql-test/main/opt_trace_security.result b/mysql-test/main/opt_trace_security.result index e1937e744a4..9223f6c0a28 100644 --- a/mysql-test/main/opt_trace_security.result +++ b/mysql-test/main/opt_trace_security.result @@ -16,7 +16,6 @@ select * from db1.t1; ERROR 42000: SELECT command denied to user 'foo'@'localhost' for table 't1' select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES - 0 1 set optimizer_trace="enabled=off"; grant select(a) on db1.t1 to 'foo'@'%'; set optimizer_trace="enabled=on"; @@ -50,19 +49,10 @@ select * from information_schema.OPTIMIZER_TRACE; QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select * from db1.t1 { "steps": [ - { - "join_preparation": { - "select_id": 1, - "steps": [ - { - "expanded_query": "select db1.t1.a AS a from t1" - } - ] - } - }, { "join_optimization": { "select_id": 1, + "expanded_query": "select db1.t1.a AS a from t1", "steps": [ { "table_dependencies": [ @@ -156,36 +146,18 @@ QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES select * from db1.v1 { "steps": [ { - "join_preparation": { + "join_optimization": { "select_id": 1, + "expanded_query": "/* select#1 */ select db1.t1.a AS a from v1", "steps": [ { "view": { "table": "v1", "select_id": 2, - "algorithm": "merged" - } - }, - { - "join_preparation": { - "select_id": 2, - "steps": [ - { - "expanded_query": "/* select#2 */ select db1.t1.a AS a from t1" - } - ] + "algorithm": "merged", + "expanded_query": "/* select#2 */ select db1.t1.a AS a from t1" } }, - { - "expanded_query": "/* select#1 */ select db1.t1.a AS a from v1" - } - ] - } - }, - { - "join_optimization": { - "select_id": 1, - "steps": [ { "table_dependencies": [ { diff --git a/sql/my_json_writer.h b/sql/my_json_writer.h index d82313f996f..20f479dc6d0 100644 --- a/sql/my_json_writer.h +++ b/sql/my_json_writer.h @@ -224,6 +224,14 @@ class Json_writer size_t get_truncated_bytes() { return output.get_truncated_bytes(); } + /* + Note: this may not return exact value due to pretty-printer doing + buffering + */ + size_t get_written_size() { + return output.length() + output.get_truncated_bytes(); + } + Json_writer() : indent_level(0), document_start(true), element_started(false), first_child(true) diff --git a/sql/opt_subselect.cc b/sql/opt_subselect.cc index d91557c5be2..953f2af0be8 100644 --- a/sql/opt_subselect.cc +++ b/sql/opt_subselect.cc @@ -549,6 +549,12 @@ bool is_materialization_applicable(THD *thd, Item_in_subselect *in_subs, and, depending on the rewrite, either do it, or record it to be done at a later phase. + NOTE + * This function called at Prepare phase. It should NOT do any rewrites. + It only collects information that's used for doing the rewrites at the + optimization phase. + * Optimizer trace is NOT yet enabled when this function is called. + RETURN 0 - OK Other - Some sort of query error @@ -703,8 +709,6 @@ int check_and_do_in_subquery_rewrites(JOIN *join) { DBUG_PRINT("info", ("Subquery is semi-join conversion candidate")); - (void)subquery_types_allow_materialization(thd, in_subs); - in_subs->is_flattenable_semijoin= TRUE; /* Register the subquery for further processing in flatten_subqueries() */ @@ -717,10 +721,6 @@ int check_and_do_in_subquery_rewrites(JOIN *join) if (arena) thd->restore_active_arena(arena, &backup); in_subs->is_registered_semijoin= TRUE; - OPT_TRACE_TRANSFORM(thd, trace_wrapper, trace_transform, - select_lex->select_number, - "IN (SELECT)", "semijoin"); - trace_transform.add("chosen", true); } } else @@ -1262,6 +1262,7 @@ bool convert_join_subqueries_to_semijoins(JOIN *join) while ((in_subq= li++)) { bool remove_item= TRUE; + (void)subquery_types_allow_materialization(thd, in_subq); /* Stop processing if we've reached a subquery that's attached to the ON clause */ if (in_subq->do_not_convert_to_sj) diff --git a/sql/opt_trace.cc b/sql/opt_trace.cc index ba9220cac44..2227519d991 100644 --- a/sql/opt_trace.cc +++ b/sql/opt_trace.cc @@ -106,6 +106,27 @@ inline bool sql_command_can_be_traced(enum enum_sql_command sql_command) sql_command == SQLCOM_UPDATE_MULTI; } + +void opt_trace_print_expanded_union(THD *thd, SELECT_LEX_UNIT *unit, + Json_writer_object *writer) +{ + DBUG_ASSERT(thd->trace_started()); + + StringBuffer<1024> str(system_charset_info); + ulonglong save_option_bits= thd->variables.option_bits; + thd->variables.option_bits &= ~OPTION_QUOTE_SHOW_CREATE; + unit->print(&str, enum_query_type(QT_TO_SYSTEM_CHARSET | + QT_SHOW_SELECT_NUMBER | + QT_ITEM_IDENT_SKIP_DB_NAMES | + QT_VIEW_INTERNAL)); + thd->variables.option_bits= save_option_bits; + /* + The output is not very pretty lots of back-ticks, the output + is as the one in explain extended , lets try to improved it here. + */ + writer->add("expanded_query", str.c_ptr_safe(), str.length()); +} + void opt_trace_print_expanded_query(THD *thd, SELECT_LEX *select_lex, Json_writer_object *writer) @@ -499,10 +520,49 @@ Opt_trace_start::Opt_trace_start(THD *thd, TABLE_LIST *tbl, } } + +/* + @brief + See "Handing Query Errors" section of comment for Opt_trace_start +*/ + +void Opt_trace_start::trace_heading_done() +{ + Json_writer *w; + if (traceable && (w= ctx->get_current_json())) + trace_heading_size= w->get_written_size(); + else + trace_heading_size= 0; +} + + +/* + @brief + See "Handing Query Errors" section of comment for Opt_trace_start + + @detail + We can't delete the trace right now, because some final writes (e.g. + the top-level closing '}' will still be made to it. Just set clean_me=true + so that it is deleted instead of saving it. +*/ + +void Opt_trace_start::clean_empty_trace() +{ + Json_writer *w; + if (traceable && (w= ctx->get_current_json())) + { + if (w->get_written_size() == trace_heading_size) + clean_me= true; + } +} + + Opt_trace_start::~Opt_trace_start() { if (traceable) { + if (clean_me) + ctx->abort_trace(); ctx->end(); traceable= FALSE; } diff --git a/sql/opt_trace.h b/sql/opt_trace.h index 101fb5f707e..c6583cdab80 100644 --- a/sql/opt_trace.h +++ b/sql/opt_trace.h @@ -69,10 +69,34 @@ struct Opt_trace_info @param query query @param length query's length @param charset charset which was used to encode this query + + @detail + == Lifecycle == + The trace is created before the Name Resolution phase. Reasons: + 1. This way, we can have one place where we start the trace for all kinds of + queries. If we tried to start tracing right before query optimization + starts, we would have to construct Opt_trace_start object in many + places: one for SELECT, for UPDATE, for DELETE, etc. + + 2. Privilege checking code may notify the trace that the user doesn't have + enough permissions to perform tracing. The trace must exist to receive + the notication. See missing_privilege() and the opt_trace_disable_if_... + functions below for details. + + == Handling Query Errors == + The trace is kept when query error occurs, except for the case when + nothing [meaningful] was traced. The second part is necessary for mtr to + produce the same output with and without --ps-protocol. If there is an + error on prepare phase, then: + - In --ps-protocol: PREPARE command produces no trace. The EXECUTE + command is not run. The trace is not generated at all. + - Regular SQL query: should also NOT produce any trace to match the above. + This is handled by trace_heading_done() and clean_empty_trace(). */ -class Opt_trace_start { +class Opt_trace_start +{ public: Opt_trace_start(THD *thd_arg, TABLE_LIST *tbl, enum enum_sql_command sql_command, @@ -82,8 +106,17 @@ class Opt_trace_start { const CHARSET_INFO *query_charset); ~Opt_trace_start(); + void trace_heading_done(); + void clean_empty_trace(); private: Opt_trace_context *const ctx; + + /* Number of bytes written to the trace after the heading was written/ */ + size_t trace_heading_size; + + /* If true, trace should be removed (See Handling Query Errors above) */ + bool clean_me= false; + /* True: the query will be traced False: otherwise @@ -102,6 +135,9 @@ class Opt_trace_start { void opt_trace_print_expanded_query(THD *thd, SELECT_LEX *select_lex, Json_writer_object *trace_object); +void opt_trace_print_expanded_union(THD *thd, SELECT_LEX_UNIT *unit, + Json_writer_object *writer); + void add_table_scan_values_to_trace(THD *thd, JOIN_TAB *tab); void trace_plan_prefix(JOIN *join, uint idx, table_map join_tables); void print_final_join_order(JOIN *join); diff --git a/sql/opt_trace_context.h b/sql/opt_trace_context.h index f578a0c67ec..ae77c94fdc2 100644 --- a/sql/opt_trace_context.h +++ b/sql/opt_trace_context.h @@ -114,6 +114,12 @@ class Opt_trace_context bool is_enabled(); + void abort_trace() + { + delete current_trace; + current_trace= NULL; + } + void missing_privilege(); static const char *flag_names[]; diff --git a/sql/sql_derived.cc b/sql/sql_derived.cc index 579ea34b8e4..cf878ad29c0 100644 --- a/sql/sql_derived.cc +++ b/sql/sql_derived.cc @@ -420,6 +420,24 @@ bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived) goto exit_merge; } + if (unlikely(thd->trace_started())) + { + /* + Add to optimizer trace whether a derived table/view + is merged into the parent select or not. + */ + OPT_TRACE_VIEWS_TRANSFORM(thd, trace_wrapper, trace_derived, + derived->is_derived() ? "derived" : "view", + derived->alias.str ? derived->alias.str : "<NULL>", + derived->get_unit()->first_select()->select_number, + derived->is_merged_derived() ? "merged" : "materialized"); + if (derived->is_merged_derived()) + { + opt_trace_print_expanded_union(thd, derived->get_unit(), + &trace_derived); + } + } + /* exclude select lex so it doesn't show up in explain. do this only for derived table as for views this is already done. @@ -822,18 +840,6 @@ bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived) } } - if (unlikely(thd->trace_started())) - { - /* - Add to optimizer trace whether a derived table/view - is merged into the parent select or not. - */ - OPT_TRACE_VIEWS_TRANSFORM(thd, trace_wrapper, trace_derived, - derived->is_derived() ? "derived" : "view", - derived->alias.str ? derived->alias.str : "<NULL>", - derived->get_unit()->first_select()->select_number, - derived->is_merged_derived() ? "merged" : "materialized"); - } /* Above cascade call of prepare is important for PS protocol, but after it is called we can check if we really need prepare for this derived diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc index b9d3eec5a60..b19ac276267 100644 --- a/sql/sql_parse.cc +++ b/sql/sql_parse.cc @@ -3648,6 +3648,7 @@ mysql_execute_command(THD *thd, bool is_called_from_prepared_stmt) Json_writer_object trace_command(thd); Json_writer_array trace_command_steps(thd, "steps"); + ots.trace_heading_done(); /* store old value of binlog format */ enum_binlog_format orig_binlog_format,orig_current_stmt_binlog_format; @@ -6154,6 +6155,9 @@ mysql_execute_command(THD *thd, bool is_called_from_prepared_stmt) thd->wsrep_PA_safe= true; #endif /* WITH_WSREP */ + if (res || thd->is_error()) + ots.clean_empty_trace(); + DBUG_RETURN(res || thd->is_error()); } diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc index cc6f572ea64..b6bc9eff50e 100644 --- a/sql/sql_prepare.cc +++ b/sql/sql_prepare.cc @@ -2435,17 +2435,6 @@ static bool check_prepared_statement(Prepared_statement *stmt) lex->first_select_lex()->context.resolve_in_table_list_only(select_lex-> get_table_list()); - /* - For the optimizer trace, this is the symmetric, for statement preparation, - of what is done at statement execution (in mysql_execute_command()). - */ - Opt_trace_start ots(thd, tables, lex->sql_command, &lex->var_list, - thd->query(), thd->query_length(), - thd->variables.character_set_client); - - Json_writer_object trace_command(thd); - Json_writer_array trace_command_steps(thd, "steps"); - /* Reset warning count for each query that uses tables */ if (tables) thd->get_stmt_da()->opt_clear_warning_info(thd->query_id); diff --git a/sql/sql_select.cc b/sql/sql_select.cc index a357d4f8c8a..45d8f54e264 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -1287,11 +1287,6 @@ JOIN::prepare(TABLE_LIST *tables_init, COND *conds_init, uint og_num, join_list= &select_lex->top_join_list; union_part= unit_arg->is_unit_op(); - Json_writer_object trace_wrapper(thd); - Json_writer_object trace_prepare(thd, "join_preparation"); - trace_prepare.add_select_number(select_lex->select_number); - Json_writer_array trace_steps(thd, "steps"); - // simple check that we got usable conds dbug_print_item(conds); @@ -1675,12 +1670,6 @@ JOIN::prepare(TABLE_LIST *tables_init, COND *conds_init, uint og_num, } } - if (thd->trace_started()) - { - Json_writer_object trace_wrapper(thd); - opt_trace_print_expanded_query(thd, select_lex, &trace_wrapper); - } - if (!procedure && result && result->prepare(fields_list, unit_arg)) goto err; /* purecov: inspected */ @@ -1985,7 +1974,11 @@ JOIN::optimize_inner() Json_writer_object trace_wrapper(thd); Json_writer_object trace_prepare(thd, "join_optimization"); - trace_prepare.add_select_number(select_lex->select_number); + if (thd->trace_started()) + { + trace_prepare.add_select_number(select_lex->select_number); + opt_trace_print_expanded_query(thd, select_lex, &trace_prepare); + } Json_writer_array trace_steps(thd, "steps"); /*