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Bug#40264: Aborted cached query causes query to hang indefinitely on next cache hit

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The problem is that the query cache was storing partial results
if the statement failed when sending the results to the client.
This could cause clients to hang when trying to read the results
from the cache as they would, for example, wait indefinitely for
a eof packet that wasn't saved.

The solution is to always discard the caching of a query that
failed to send its results to the associated client.
This commit is contained in:
Davi Arnaut 2009-01-22 08:28:01 -02:00
parent 7fc8286257
commit 6a834d1f4f
3 changed files with 53 additions and 1 deletions
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16
mysql-test/r/query_cache_notembedded.result
View file

@ -345,3 +345,19 @@ id
drop table t1;
drop function f1;
set GLOBAL query_cache_size=0;
DROP TABLE IF EXISTS t1;
FLUSH STATUS;
SET GLOBAL query_cache_size=1048576;
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2),(3),(4),(5);
SHOW STATUS LIKE 'Qcache_queries_in_cache';
Variable_name Value
Qcache_queries_in_cache 0
LOCK TABLES t1 WRITE;
SELECT * FROM t1;
UNLOCK TABLES;
SHOW STATUS LIKE 'Qcache_queries_in_cache';
Variable_name Value
Qcache_queries_in_cache 0
DROP TABLE t1;
SET GLOBAL query_cache_size= default;

31
mysql-test/t/query_cache_notembedded.test
View file

@ -222,3 +222,34 @@ disconnect con2;
connection default;
set GLOBAL query_cache_size=0;
#
# Bug#40264: Aborted cached query causes query to hang indefinitely on next cache hit
#
--disable_warnings
DROP TABLE IF EXISTS t1;
--enable_warnings
FLUSH STATUS;
SET GLOBAL query_cache_size=1048576;
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2),(3),(4),(5);
SHOW STATUS LIKE 'Qcache_queries_in_cache';
LOCK TABLES t1 WRITE;
connect(con1,localhost,root,,);
--send SELECT * FROM t1
connection default;
let $show_type= open tables where `table`='t1' and in_use=2;
let $show_pattern= '%t1%2%';
--source include/wait_show_pattern.inc
dirty_close con1;
UNLOCK TABLES;
let $show_type= open tables where `table`='t1' and in_use=0;
let $show_pattern= '%t1%0%';
--source include/wait_show_pattern.inc
SHOW STATUS LIKE 'Qcache_queries_in_cache';
DROP TABLE t1;
SET GLOBAL query_cache_size= default;
# End of 5.0 tests

7
sql/sql_cache.cc
View file

@ -710,7 +710,12 @@ void query_cache_end_of_result(THD *thd)
if (thd->net.query_cache_query == 0)
DBUG_VOID_RETURN;
if (thd->killed)
/*
Check if the NET layer raised a unreported error -- my_error() and
as a consequence query_cache_abort() haven't been called. Abort the
cached result as it might be only partially complete.
*/
if (thd->killed || thd->net.report_error)
{
query_cache_abort(&thd->net);
DBUG_VOID_RETURN;