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MDEV-24823 Crash with invalid multi-table update of view in 2nd execution of SP

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Before this patch mergeable derived tables / view used in a multi-table
update / delete were merged before the preparation stage.
When the merge of a derived table / view is performed the on expression
attached to it is fixed and ANDed with the where condition of the select S
containing this derived table / view. It happens after the specification of
the derived table / view has been merged into S. If the ON expression refers
to a non existing field an error is reported and some other mergeable derived
tables / views remain unmerged. It's not a problem if the multi-table
update / delete statement is standalone. Yet if it is used in a stored
procedure the select with incompletely merged derived tables / views may
cause a problem for the second call of the procedure. This does not happen
for select queries using derived tables / views, because in this case their
specifications are merged after the preparation stage at which all ON
expressions are fixed.
This patch makes sure that merging of the derived tables / views used in a
multi-table update / delete statement is performed after the preparation
stage.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
This commit is contained in:
Igor Babaev
2021-04-22 20:02:08 -07:00
parent 6f271302b6
commit e3a25793be
7 changed files with 147 additions and 25 deletions
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15
sql/sql_delete.cc
View File

@ -1009,9 +1009,6 @@ int mysql_multi_delete_prepare(THD *thd)
DELETE_ACL, SELECT_ACL, FALSE))
DBUG_RETURN(TRUE);
if (lex->select_lex.handle_derived(thd->lex, DT_MERGE))
DBUG_RETURN(TRUE);
/*
Multi-delete can't be constructed over-union => we always have
single SELECT on top and have to check underlying SELECTs of it
@ -1039,6 +1036,12 @@ int mysql_multi_delete_prepare(THD *thd)
target_tbl->table_name.str, "DELETE");
DBUG_RETURN(TRUE);
}
}
for (target_tbl= (TABLE_LIST*) aux_tables;
target_tbl;
target_tbl= target_tbl->next_local)
{
/*
Check that table from which we delete is not used somewhere
inside subqueries/view.
@ -1083,12 +1086,6 @@ multi_delete::prepare(List<Item> &values, SELECT_LEX_UNIT *u)
unit= u;
do_delete= 1;
THD_STAGE_INFO(thd, stage_deleting_from_main_table);
SELECT_LEX *select_lex= u->first_select();
if (select_lex->first_cond_optimization)
{
if (select_lex->handle_derived(thd->lex, DT_MERGE))
DBUG_RETURN(TRUE);
}
DBUG_RETURN(0);
}