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MDEV-39505: Diff in rows column of explain plan for delete table stmt #5063

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MDEV-39505: Diff in rows column of explain plan for delete table stmt #5063

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22 changes: 22 additions & 0 deletions mysql-test/main/opt_context_replay_basic.result
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Original file line number Diff line number Diff line change
Expand Up @@ -253,6 +253,7 @@ select context into dumpfile "../../tmp/dump1.sql"
from information_schema.optimizer_context;
set optimizer_record_context=OFF;
drop table t1;
set optimizer_replay_context='';
drop table t1;
#
# MDEV-39409: Context replay doesnt handle MIN/MAX optimization
Expand All @@ -272,5 +273,26 @@ set optimizer_replay_context='opt_context';
EXPLAIN SELECT MAX(a) FROM t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
set optimizer_replay_context='';
drop table t1;
#
# MDEV-39505: Explain delete all from table shows difference in number of rows
#
create table t1 (c1 integer);
insert into t1 values (1), (2), (3);
set optimizer_record_context=1;
explain delete from t1 order by c1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL 3 Deleting all rows
select context into dumpfile "../../tmp/dump1.sql"
from information_schema.optimizer_context;
set optimizer_record_context=0;
drop table t1;
set optimizer_replay_context='opt_context';
# Same query as above, must have same explain:
explain delete from t1 order by c1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL 3 Deleting all rows
set optimizer_replay_context='';
drop table t1;
drop database db1;
28 changes: 28 additions & 0 deletions mysql-test/main/opt_context_replay_basic.test
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,7 @@ drop table t1;
--enable_query_log
--enable_result_log

set optimizer_replay_context='';
--remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
drop table t1;

Expand All @@ -116,6 +117,33 @@ set optimizer_replay_context='opt_context';
--echo # Same query as above, must have same explain:
EXPLAIN SELECT MAX(a) FROM t1;

set optimizer_replay_context='';
--remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
drop table t1;

--echo #
--echo # MDEV-39505: Explain delete all from table shows difference in number of rows
--echo #
create table t1 (c1 integer);
insert into t1 values (1), (2), (3);

set optimizer_record_context=1;
explain delete from t1 order by c1;

select context into dumpfile "../../tmp/dump1.sql"
from information_schema.optimizer_context;
set optimizer_record_context=0;
drop table t1;
--disable_query_log
--disable_result_log
--source "$MYSQLTEST_VARDIR/tmp/dump1.sql"
--enable_query_log
--enable_result_log
set optimizer_replay_context='opt_context';
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@gemini-code-assist gemini-code-assist Bot May 11, 2026

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medium

The context name 'opt_context' used here appears to be carried over from the previous test case (see line 115, not shown in this diff). Since the current test records the context using set optimizer_record_context=1 at line 130 (which uses the default empty name), this command might be replaying the wrong context from a previous query instead of the DELETE query just recorded. To ensure test isolation and validity, please use the default name for both recording and replaying, or use a unique name for both.

set optimizer_replay_context='';

--echo # Same query as above, must have same explain:
explain delete from t1 order by c1;

set optimizer_replay_context='';
--remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
drop table t1;

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1 change: 1 addition & 0 deletions sql/sql_delete.cc
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Expand Up @@ -527,6 +527,7 @@ bool Sql_cmd_delete::delete_from_single_table(THD *thd)
{
/* Update the table->file->stats.records number */
table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
set_statistics_for_table(thd, table);
ha_rows const maybe_deleted= table->file->stats.records;
DBUG_PRINT("debug", ("Trying to use delete_all_rows()"));

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