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MDEV-35571 Check for LIMIT ROWS EXAMINED exceeded in UNION ALL

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When UNION ALL is used with LIMIT ROWS EXAMINED, and when the limit is
exceeded for a SELECT that is not the last in the UNION, interrupt the
execution and call end_eof on the result. This makes sure that the
results are sent, and the query result status is conclusive rather
than empty, which would cause an assertion failure.
This commit is contained in:
Yuchen Pei 2024-12-09 19:27:53 +11:00
parent 3e34e4c161
commit 432856c473
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GPG key ID: 3DD1B35105743563
3 changed files with 86 additions and 1 deletions
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43
mysql-test/main/limit_rows_examined.result
View file

@ -895,3 +895,46 @@ Warnings:
Note 1003 select `test`.`t1`.`c1` AS `c1`,`test`.`t2`.`c2` AS `c2` from `test`.`t1` join `test`.`t2` where `test`.`t2`.`c2` = `test`.`t1`.`c1`
drop table t1,t2;
# End of 10.4 tests
#
# MDEV-35571: Connection hangs after query on a partitioned table with UNION and LIMIT ROWS EXAMINED
#
create table t1 (a int);
insert into t1 values (1), (2);
select * from t1 UNION ALL select * from t1 LIMIT ROWS EXAMINED 1;
a
1
Warnings:
Warning 1931 Query execution was interrupted. The query exceeded LIMIT ROWS EXAMINED 1. The query result may be incomplete
select * from t1 UNION DISTINCT select * from t1 LIMIT ROWS EXAMINED 1;
a
1
Warnings:
Warning 1931 Query execution was interrupted. The query exceeded LIMIT ROWS EXAMINED 1. The query result may be incomplete
DROP TABLE t1;
create table t1 (a int);
insert into t1 values (1), (2);
(select a from t1 UNION ALL select a from t1) order by a desc LIMIT ROWS EXAMINED 2;
a
1
Warnings:
Warning 1931 Query execution was interrupted. The query exceeded LIMIT ROWS EXAMINED 2. The query result may be incomplete
(select a from t1 UNION DISTINCT select a from t1) order by a desc LIMIT ROWS EXAMINED 2;
a
1
Warnings:
Warning 1931 Query execution was interrupted. The query exceeded LIMIT ROWS EXAMINED 2. The query result may be incomplete
DROP TABLE t1;
CREATE TABLE t1 (a INT);
INSERT INTO t1 SELECT seq%25 FROM seq_1_to_100;
CREATE TABLE t2 (b INT, c INT, KEY(b)) PARTITION BY HASH(c) PARTITIONS 12;
INSERT INTO t2 SELECT seq, seq FROM seq_1_to_10;
SELECT COUNT(*) FROM t1 JOIN t2 ON (b = a) UNION ALL SELECT COUNT(*) FROM t1 JOIN t2 ON (b = a) LIMIT ROWS EXAMINED 100;
COUNT(*)
Warnings:
Warning 1931 Query execution was interrupted. The query exceeded LIMIT ROWS EXAMINED 100. The query result may be incomplete
SELECT COUNT(*) FROM t1 JOIN t2 ON (b = a) UNION DISTINCT SELECT COUNT(*) FROM t1 JOIN t2 ON (b = a) LIMIT ROWS EXAMINED 100;
COUNT(*)
Warnings:
Warning 1931 Query execution was interrupted. The query exceeded LIMIT ROWS EXAMINED 100. The query result may be incomplete
DROP TABLE t1, t2;
# End of 10.5 tests

41
mysql-test/main/limit_rows_examined.test
View file

@ -617,3 +617,44 @@ select * from t1, t2 where c1 = c2 LIMIT ROWS EXAMINED 2;
drop table t1,t2;
--echo # End of 10.4 tests
--echo #
--echo # MDEV-35571: Connection hangs after query on a partitioned table with UNION and LIMIT ROWS EXAMINED
--echo #
--source include/have_partition.inc
--source include/have_sequence.inc
# Simplified test
create table t1 (a int);
insert into t1 values (1), (2);
select * from t1 UNION ALL select * from t1 LIMIT ROWS EXAMINED 1;
# UNION DISTINCT produces the same result here. Note that this is not
# affected by the MDEV-35571 patch
select * from t1 UNION DISTINCT select * from t1 LIMIT ROWS EXAMINED 1;
DROP TABLE t1;
# Simplified test with order by
create table t1 (a int);
insert into t1 values (1), (2);
(select a from t1 UNION ALL select a from t1) order by a desc LIMIT ROWS EXAMINED 2;
# UNION DISTINCT produces the same result with order by desc. Note
# that this is not affected by the MDEV-35571 patch
(select a from t1 UNION DISTINCT select a from t1) order by a desc LIMIT ROWS EXAMINED 2;
DROP TABLE t1;
# Original test
CREATE TABLE t1 (a INT);
INSERT INTO t1 SELECT seq%25 FROM seq_1_to_100;
CREATE TABLE t2 (b INT, c INT, KEY(b)) PARTITION BY HASH(c) PARTITIONS 12;
INSERT INTO t2 SELECT seq, seq FROM seq_1_to_10;
SELECT COUNT(*) FROM t1 JOIN t2 ON (b = a) UNION ALL SELECT COUNT(*) FROM t1 JOIN t2 ON (b = a) LIMIT ROWS EXAMINED 100;
# UNION DISTINCT produces the same result here. Note that this is not
# affected by the MDEV-35571 patch
SELECT COUNT(*) FROM t1 JOIN t2 ON (b = a) UNION DISTINCT SELECT COUNT(*) FROM t1 JOIN t2 ON (b = a) LIMIT ROWS EXAMINED 100;
DROP TABLE t1, t2;
--echo # End of 10.5 tests

3
sql/sql_union.cc
View file

@ -1026,7 +1026,8 @@ bool select_union_direct::send_eof()
// Reset for each SELECT_LEX, so accumulate here
limit_found_rows+= thd->limit_found_rows;
if (unit->thd->lex->current_select == last_select_lex)
if (unit->thd->lex->current_select == last_select_lex ||
thd->killed == ABORT_QUERY)
{
thd->limit_found_rows= limit_found_rows;