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MDEV-31361 Wrong result on 2nd execution of PS for query with derived table

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This bug led to wrong result sets returned by the second execution of
prepared statements from selects using mergeable derived tables pushed
into external engine. Such derived tables are always materialized. The
decision that they have to be materialized is taken late in the function
mysql_derived_optimized(). For regular derived tables this decision is
usually taken at the prepare phase. However in some cases for some derived
tables this decision is made in mysql_derived_optimized() too. It can be
seen in the code of mysql_derived_fill() that for such a derived table it's
critical to change its translation table to tune it to the fields of the
temporary table used for materialization of the derived table and this
must be done after each refill of the derived table. The same actions are
needed for derived tables pushed into external engines.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
This commit is contained in:
Igor Babaev
2024-02-02 20:33:40 -08:00
parent 9d0b79c5f5
commit 6fadbf8ebf
3 changed files with 126 additions and 3 deletions
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3
sql/sql_derived.cc
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@ -1217,7 +1217,9 @@ bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived)
/* Execute the query that specifies the derived table by a foreign engine */
res= derived->pushdown_derived->execute();
unit->executed= true;
if (res)
DBUG_RETURN(res);
goto after_exec;
}
if (unit->executed && !derived_is_recursive &&
@ -1278,6 +1280,7 @@ bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived)
derived_result, unit, first_select);
}
after_exec:
if (!res && !derived_is_recursive)
{
if (derived_result->flush())