[MDEV-178] LIMIT ROWS EXAMINED: Assertion `0' failed in net_end_statement(THD*) on the 2nd PS execution, with DISTINCT, FROM subquery or view in SELECT, JOIN in nested subquery Created: 2012-03-11  Updated: 2012-03-11  Resolved: 2012-03-11

Status: Closed
Project: MariaDB Server
Component/s: None
Affects Version/s: None
Fix Version/s: 5.5.21

Type: Bug Priority: Major
Reporter: Elena Stepanova Assignee: Timour Katchaounov (Inactive)
Resolution: Fixed Votes: 0
Labels: None

Issue Links:
Relates
relates to MDEV-28 LIMIT ROWS EXAMINED clause to limit t... Closed

 Description   

mysqld: protocol.cc:509: void net_end_statement(THD*): Assertion `0' failed.
 
#6  0x00007f8116add235 in __assert_fail () from /lib64/libc.so.6
#7  0x00000000006d5e99 in net_end_statement (thd=0x1c73ae8) at protocol.cc:509
#8  0x00000000006f4b90 in dispatch_command (command=COM_QUERY, thd=0x1c73ae8, packet=0x1caaff9 "EXECUTE ps", 
    packet_length=10) at sql_parse.cc:1620
#9  0x00000000006f2b38 in do_command (thd=0x1c73ae8) at sql_parse.cc:923
#10 0x00000000006efa16 in handle_one_connection (arg=0x1c73ae8) at sql_connect.cc:1193
#11 0x00007f8117798a4f in start_thread () from /lib64/libpthread.so.0
#12 0x00007f8116b8282d in clone () from /lib64/libc.so.6

bzr version-info

revision-id: timour@askmonty.org-20120309222351-jlq0uf1narp45gep
date: 2012-03-10 00:23:51 +0200
build-date: 2012-03-11 07:38:33 +0200
revno: 3456

Minimal optimizer_switch:

in_to_exists=on

Full optimizer_switch (default):

index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on

EXPLAIN for the SELECT:

id      select_type     table   type    possible_keys   key     key_len ref     rows    filtered        Extra
1       PRIMARY <derived2>      ALL     NULL    NULL    NULL    NULL    2       100.00
2       DERIVED t1      ALL     NULL    NULL    NULL    NULL    2       100.00  Using where; Using temporary
3       SUBQUERY        t1      ALL     NULL    NULL    NULL    NULL    2       100.00
3       SUBQUERY        t2      ALL     NULL    NULL    NULL    NULL    3       100.00  Using where; Using join buffer (flat, BNL join)
Warnings:
Note    1003    select `v`.`a` AS `a` from `test`.`v`

Test case:

SET optimizer_switch = 'in_to_exists=on';
 
CREATE TABLE t1 ( a INT );
INSERT INTO t1 VALUES (2),(150);
CREATE TABLE t2 ( b INT );
INSERT INTO t2 VALUES (2),(17),(6);
 
CREATE VIEW v AS
SELECT DISTINCT * FROM t1
WHERE a = ( SELECT COUNT(*) FROM t1, t2 WHERE a = b );
 
PREPARE ps FROM
'SELECT * FROM v LIMIT ROWS EXAMINED 10';
 
EXECUTE ps;
EXECUTE ps;



 Comments   
Comment by Timour Katchaounov (Inactive) [ 2012-03-11 ]

The same problem as mdev-174. The fix is to generalize the solution of mdev-174, so that it tests that limit rows is enabled for the outermost select, and not just test that there is no unit->item.

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