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MDEV-22042 Server crash in Item_field::print on ANALYZE FORMAT=JSON

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When processing a query with a recursive CTE a temporary table is used for
each recursive reference of the CTE. As any temporary table it uses its own
mem-root for table definition structures. Due to specifics of the current
implementation of ANALYZE stmt command this mem-root can be freed only at
the very of query processing. Such deallocation of mem-root memory happens
in close_thread_tables(). The function looks through the list of the tmp
tables rec_tables attached to the THD of the query and frees corresponding
mem-roots. If the query uses a stored function then such list is created
for each query of the function. When a new rec_list has to be created the
old one has to be saved and then restored at the proper moment.
The bug occurred because only one rec_list for the query containing CTE was
created. As a result close_thread_tables() freed tmp mem-roots used for
rec_tables prematurely destroying some data needed for the output produced
by the ANALYZE command.
This commit is contained in:
Igor Babaev
2020-06-05 10:38:40 -07:00
parent fff7897e3a
commit a8c200c73c
3 changed files with 205 additions and 0 deletions
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39
mysql-test/t/cte_recursive.test
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@ -2536,3 +2536,42 @@ with recursive cte as
select * from t1 as t;
drop table t1,t2;
--echo #
--echo # MDEV-22042: ANALYZE of query using stored function and recursive CTE
--echo #
create table t1 (a1 varchar(20),a2 varchar(20)) engine=myisam;
insert into t1 values (1,1),(2,2),(3,3);
create table t2 (
a2 varchar(20) primary key, b1 varchar(20), key (b1)
) engine=myisam;
insert into t2 values (1,1),(2,2),(3,3),(4,4),(5,5),(6,6),(7,7);
insert into t2 values (11,11),(12,12),(13,13),(14,14),(15,15),(16,16),(17,17);
delimiter $$;
create function f1(id varchar(20)) returns varchar(50)
begin
declare res varchar (50);
select a2 into res from t2 where a2=id and b1=1 limit 1;
return res;
end$$
delimiter ;$$
let q=
select fv
from (select t1.a1, f1(t1.a2) fv from t1) dt
where (dt.a1) in (with recursive cte as (select a2 from t2 where a2='2'
union select tt2.a2 from t2 tt2 join cte on tt2.b1=cte.a2)
select a2 from cte);
eval $q;
eval explain $q;
--source include/analyze-format.inc
eval analyze format=json $q;
drop function f1;
drop table t1,t2;
--echo End of 10.2 tests