Hi! See small comment inline. (fix and OK to push) Am 15.08.2018 um 13:36 schrieb Sergey Petrunia:

MDEV-6439: Server crashes in Explain_union::print_explain with explain in slow log, tis620 charset

Item_subselect::is_expensive() used to return FALSE (Inexpensive) whenever it saw that one of SELECTs in the Subquery's UNION is degenerate. It ignored the fact that other parts of the UNION might not be inexpensive, including the case where pther parts of the UNION have no query plan yet.

For a subquery in form col >= ANY (SELECT 'foo' UNION SELECT 'bar') this would cause the query to be considered inexpensive when there is no query plan for the second part of the UNION, which in turn would cause the SELECT 'foo' to compute and free itself while still inside JOIN::optimize for that SELECT (See MDEV comment for full description).

diff --git a/mysql-test/r/subselect_extra_no_semijoin.result b/mysql-test/r/subselect_extra_no_semijoin.result index 79bca38..200682b 100644 --- a/mysql-test/r/subselect_extra_no_semijoin.result +++ b/mysql-test/r/subselect_extra_no_semijoin.result @@ -482,3 +482,22 @@ DROP TABLE t1,t2; set optimizer_switch= @tmp_subselect_extra_derived; set optimizer_switch= @subselect_extra_no_sj_tmp; set @optimizer_switch_for_subselect_extra_test=null; +# +# MDEV-6439: Server crashes in Explain_union::print_explain with explain in slow log, tis620 charset +# +SET NAMES tis620; +set @tmp= @@global.slow_query_log; +SET GLOBAL slow_query_log = 1; +SET long_query_time = 0.000001; +SET log_slow_verbosity = 'explain'; +CREATE TABLE t1 (a VARCHAR(3)) ENGINE=MyISAM; +SELECT * FROM t1 WHERE a >= ANY ( SELECT 'foo'); +a +SELECT * FROM t1 WHERE a >= ANY ( SELECT 'foo' UNION SELECT 'bar' ); +ERROR HY000: Illegal mix of collations (tis620_thai_ci,COERCIBLE) and (latin1_swedish_ci,IMPLICIT) for operation '<=' +create table t2 (b int); +insert into t2 values (1),(2),(3); +SELECT * FROM t1 WHERE a >= ANY ( SELECT 'foo' FROM t2); +ERROR HY000: Illegal mix of collations (tis620_thai_ci,COERCIBLE) and (latin1_swedish_ci,IMPLICIT) for operation '<=' +drop table t1,t2; +SET GLOBAL slow_query_log=@tmp; diff --git a/mysql-test/t/subselect_extra_no_semijoin.test b/mysql-test/t/subselect_extra_no_semijoin.test index 8aba3dd..41593fb 100644 --- a/mysql-test/t/subselect_extra_no_semijoin.test +++ b/mysql-test/t/subselect_extra_no_semijoin.test @@ -6,4 +6,34 @@ set @optimizer_switch_for_subselect_extra_test='semijoin=off,firstmatch=off,loo

set optimizer_switch= @subselect_extra_no_sj_tmp;

-set @optimizer_switch_for_subselect_extra_test=null; \ No newline at end of file +set @optimizer_switch_for_subselect_extra_test=null; + +--echo # +--echo # MDEV-6439: Server crashes in Explain_union::print_explain with explain in slow log, tis620 charset +--echo # + +## Using a separate client connection is easier than restoring state +connect(con1,localhost,root,,); + +SET NAMES tis620; +set @tmp= @@global.slow_query_log; +SET GLOBAL slow_query_log = 1; +SET long_query_time = 0.000001; +SET log_slow_verbosity = 'explain'; +

please remove above space at the end of line and push.

+CREATE TABLE t1 (a VARCHAR(3)) ENGINE=MyISAM; +SELECT * FROM t1 WHERE a >= ANY ( SELECT 'foo'); +--error ER_CANT_AGGREGATE_2COLLATIONS +SELECT * FROM t1 WHERE a >= ANY ( SELECT 'foo' UNION SELECT 'bar' ); + +create table t2 (b int); +insert into t2 values (1),(2),(3); + +--error ER_CANT_AGGREGATE_2COLLATIONS +SELECT * FROM t1 WHERE a >= ANY ( SELECT 'foo' FROM t2); + +drop table t1,t2; +SET GLOBAL slow_query_log=@tmp; +disconnect con1; +connection default; + diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc index a8dfdff..14b2ccd 100644 --- a/sql/item_subselect.cc +++ b/sql/item_subselect.cc @@ -575,7 +575,7 @@ bool Item_subselect::is_expensive() */ if (cur_join->optimized && (cur_join->zero_result_cause || !cur_join->tables_list)) - return false; + continue;

/* If a subquery is not optimized we cannot estimate its cost. A subquery is