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MDEV-37252 Do not check is_key_used in get_index_for_order

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This allows UPDATE to use ORDER BY indexes in the update columns.
This commit is contained in:
Yuchen Pei
2025-07-17 15:15:36 +10:00
parent ce7ab467db
commit 7215fe7894
3 changed files with 4 additions and 5 deletions
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2
mysql-test/main/explain_non_select.result
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@ -72,7 +72,7 @@ id select_type table type possible_keys key key_len ref rows Extra
# This should use an index, possible_keys=NULL because there is no WHERE # This should use an index, possible_keys=NULL because there is no WHERE
explain update t1 set a=a+1 order by a limit 2; explain update t1 set a=a+1 order by a limit 2;
id select_type table type possible_keys key key_len ref rows Extra id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 512 Using filesort 1 SIMPLE t1 index NULL a 5 NULL 2 Using buffer
# This should use range, possible_keys={a,b} # This should use range, possible_keys={a,b}
explain update t1 set filler='fooo' where a<20 and b < 10; explain update t1 set filler='fooo' where a<20 and b < 10;
id select_type table type possible_keys key key_len ref rows Extra id select_type table type possible_keys key key_len ref rows Extra

4
mysql-test/main/update.result
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@ -288,7 +288,7 @@ update t1 set a=9999 order by a limit 1;
update t1 set b=9999 order by a limit 1; update t1 set b=9999 order by a limit 1;
show status like 'handler_read%'; show status like 'handler_read%';
Variable_name Value Variable_name Value
Handler_read_first 1 Handler_read_first 2
Handler_read_key 0 Handler_read_key 0
Handler_read_last 0 Handler_read_last 0
Handler_read_next 0 Handler_read_next 0
@ -296,7 +296,7 @@ Handler_read_prev 0
Handler_read_retry 0 Handler_read_retry 0
Handler_read_rnd 2 Handler_read_rnd 2
Handler_read_rnd_deleted 0 Handler_read_rnd_deleted 0
Handler_read_rnd_next 9 Handler_read_rnd_next 0
flush status; flush status;
delete from t1 order by a limit 1; delete from t1 order by a limit 1;
show status like 'handler_read%'; show status like 'handler_read%';

3
sql/sql_select.cc
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@ -33411,8 +33411,7 @@ uint get_index_for_order(ORDER *order, TABLE *table, SQL_SELECT *select,
double new_cost; double new_cost;
if (test_if_cheaper_ordering(FALSE, NULL, order, table, if (test_if_cheaper_ordering(FALSE, NULL, order, table,
table->keys_in_use_for_order_by, -1, limit, table->keys_in_use_for_order_by, -1, limit,
&key, &direction, &limit, &new_cost) && &key, &direction, &limit, &new_cost))
!is_key_used(table, key, table->write_set))
{ {
*need_sort= FALSE; *need_sort= FALSE;
*scanned_limit= limit; *scanned_limit= limit;