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MDEV-28965 Assertion failure when preparing UPDATE with derived table in WHERE

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This patch fixes not only the assertion failure in the function
Field_iterator_table_ref::set_field_iterator() but also:
 - fixes the problem of forced materialization of derived tables used
   in subqueries contained in WHERE clauses of single-table and multi-table
   UPDATE and DELETE statements
 - fixes the problem of MDEV-17954 that prevented execution of multi-table
   DELETE statements if they use in their WHERE clauses references to
   the tables that are updated.

The patch must be considered a complement to the patch for MDEV-28883.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
This commit is contained in:
Igor Babaev
2022-07-11 16:57:37 -07:00
parent 3a9358a410
commit 88ca62dc68
27 changed files with 1106 additions and 79 deletions
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56
sql/opt_subselect.cc
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@@ -30,6 +30,8 @@
#include "sql_base.h"
#include "sql_const.h"
#include "sql_select.h"
#include "sql_update.h" // class Sql_cmd_update
#include "sql_delete.h" // class Sql_cmd_delete
#include "filesort.h"
#include "opt_subselect.h"
#include "sql_test.h"
@@ -534,6 +536,48 @@ bool is_materialization_applicable(THD *thd, Item_in_subselect *in_subs,
return FALSE;
}
/**
@brief Check whether an IN subquery must be excluded from conversion to SJ
@param thd global context the processed statement
@returns true if the IN subquery must be excluded from conversion to SJ
@note
Currently a top level IN subquery of an delete statement is not converted
to SJ if the statement contains ORDER BY ... LIMIT or contains RETURNING.
@todo
The disjunctive members
!((Sql_cmd_update *) cmd)->is_multitable()
!((Sql_cmd_delete *) cmd)->is_multitable()
will be removed when conversions of IN predicands to semi-joins are
fully supported for single-table UPDATE/DELETE statements.
*/
bool SELECT_LEX::is_sj_conversion_prohibited(THD *thd)
{
DBUG_ASSERT(master_unit()->item->substype() == Item_subselect::IN_SUBS);
SELECT_LEX *outer_sl= outer_select();
if (outer_sl->outer_select())
return false;
Sql_cmd *cmd= thd->lex->m_sql_cmd;
switch (thd->lex->sql_command) {
case SQLCOM_UPDATE:
return
!((Sql_cmd_update *) cmd)->is_multitable() ||
((Sql_cmd_update *) cmd)->processing_as_multitable_update_prohibited(thd);
case SQLCOM_DELETE:
return
!((Sql_cmd_delete *) cmd)->is_multitable() ||
((Sql_cmd_delete *) cmd)->processing_as_multitable_delete_prohibited(thd);
default:
return false;
}
}
/*
Check if we need JOIN::prepare()-phase subquery rewrites and if yes, do them
@@ -677,9 +721,8 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
3. Subquery does not have GROUP BY or ORDER BY
4. Subquery does not use aggregate functions or HAVING
5. Subquery predicate is at the AND-top-level of ON/WHERE clause
6. We are not in a subquery of a single table UPDATE/DELETE that
doesn't have a JOIN (TODO: We should handle this at some
point by switching to multi-table UPDATE/DELETE)
6. We are not in a subquery of a single-table UPDATE/DELETE that
does not allow conversion to multi-table UPDATE/DELETE
7. We're not in a table-less subquery like "SELECT 1"
8. No execution method was already chosen (by a prepared statement)
9. Parent select is not a table-less select
@@ -698,9 +741,7 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
!select_lex->group_list.elements && !join->order && // 3
!join->having && !select_lex->with_sum_func && // 4
in_subs->emb_on_expr_nest && // 5
select_lex->outer_select()->join && // 6
(!thd->lex->m_sql_cmd ||
thd->lex->m_sql_cmd->sql_command_code() == SQLCOM_UPDATE_MULTI) &&
!select_lex->is_sj_conversion_prohibited(thd) && // 6
parent_unit->first_select()->leaf_tables.elements && // 7
!in_subs->has_strategy() && // 8
select_lex->outer_select()->table_list.first && // 9
@@ -760,7 +801,8 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
*/
if (in_subs && !in_subs->has_strategy())
{
if (is_materialization_applicable(thd, in_subs, select_lex))
if (!select_lex->is_sj_conversion_prohibited(thd) &&
is_materialization_applicable(thd, in_subs, select_lex))
{
in_subs->add_strategy(SUBS_MATERIALIZATION);