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MDEV-24242 Query returns wrong result while using big_tables=1

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When executing set operations in a pipeline using only one temporary table
additional scans of intermediate results may be needed. The scans are
performed with usage of the rnd_next() handler function that might
leave record buffers used for the temporary table not in a state that
is good for following writes into the table. For example it happens for
aria engine when the last call of rnd_next() encounters only deleted
records. Thus a cleanup of record buffers is needed after each such scan
of the temporary table.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
This commit is contained in:
Igor Babaev 2020-11-24 20:05:54 -08:00
commit b92391d5b1
3 changed files with 66 additions and 0 deletions
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34
mysql-test/main/set_operation.result
View file

@ -1155,3 +1155,37 @@ count(*)
319
drop table t1;
drop table t2;
#
# MDEV-24242: set expression with empty intermediate result
# when tmp_memory_table_size is set to 0
#
create table t1 (a int, b int) engine=MyISAM;
insert into t1 values (1,1), (2,2);
create table t2 (a int, b int) engine=MyISAM;
insert into t2 values (11,11), (12,12), (13,13);
select * from t1
except all
select * from t1
except
select * from t1
union all
select * from t2;
a b
12 12
11 11
13 13
set tmp_memory_table_size=0;
select * from t1
except all
select * from t1
except
select * from t1
union all
select * from t2;
a b
12 12
11 11
13 13
set tmp_memory_table_size=default;
drop table t1,t2;
# End of 10.4 tests

28
mysql-test/main/set_operation.test
View file

@ -524,3 +524,31 @@ select count(*) from
drop table t1;
drop table t2;
--echo #
--echo # MDEV-24242: set expression with empty intermediate result
--echo # when tmp_memory_table_size is set to 0
--echo #
create table t1 (a int, b int) engine=MyISAM;
insert into t1 values (1,1), (2,2);
create table t2 (a int, b int) engine=MyISAM;
insert into t2 values (11,11), (12,12), (13,13);
let $q=
select * from t1
except all
select * from t1
except
select * from t1
union all
select * from t2;
eval $q;
set tmp_memory_table_size=0;
eval $q;
set tmp_memory_table_size=default;
drop table t1,t2;
--echo # End of 10.4 tests

4
sql/sql_union.cc
View file

@ -880,6 +880,10 @@ bool select_unit_ext::send_eof()
table->file->ha_rnd_end();
}
/* Clean up table buffers for the next set operation from pipeline */
if (next_sl)
restore_record(table,s->default_values);
if (unlikely(error))
table->file->print_error(error, MYF(0));