mariadb/mysql-test/t/query_cache_28249.test

### t/query_cache_28249.test ###
#
# Test for
# Bug#28249 Query Cache returns wrong result with concurrent insert / certain lock
#
# Last modification:
# 2008-11-27 mleich - Move this test out of query_cache.test
#                   - Fix Bug#40179 Test main.query_cache failing randomly on Pushbuild,
#                                   test weakness
#                   - Minor improvements (comments,formatting etc.)
#

--source include/have_query_cache.inc
--source include/not_embedded.inc

SET @query_cache_type=         @@global.query_cache_type;
SET @query_cache_limit=        @@global.query_cache_limit;
SET @query_cache_min_res_unit= @@global.query_cache_min_res_unit;
SET @query_cache_size=         @@global.query_cache_size;

--echo # Bug#28249 Query Cache returns wrong result with concurrent insert/ certain lock
--echo # Establish connections user1,user2,user3 (user=root)
connect (user1,localhost,root,,test,,);
connect (user2,localhost,root,,test,,);
connect (user3,localhost,root,,test,,);

--echo # Switch to connection user1
connection user1;

SET GLOBAL query_cache_type=1;
SET GLOBAL query_cache_limit=10000;
SET GLOBAL query_cache_min_res_unit=0;
SET GLOBAL query_cache_size= 100000;

FLUSH TABLES;
--disable_warnings
DROP TABLE IF EXISTS t1, t2;
--enable_warnings
CREATE TABLE t1 (a INT);
CREATE TABLE t2 (a INT);
INSERT INTO t1 VALUES (1),(2),(3);

--echo # Switch to connection user2
connection user2;
LOCK TABLE t2 WRITE;

--echo # Switch to connection user1
connection user1;
--echo # "send" the next select, "reap" the result later.
--echo # The select will be blocked by the write lock on the t1.
let $select_for_qc =
SELECT *, (SELECT COUNT(*) FROM t2) FROM t1;
send;
eval $select_for_qc;

--echo # Switch to connection user3
connection user3;
# Typical information_schema.processlist content after sufficient sleep time
#   ID  USER  COMMAND  TIME  STATE   INFO
#   ....
#   2   root  Query       5  Locked  SELECT *, (SELECT COUNT(*) FROM t2) FROM t1
#   ....
#                            XXXXXX  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
# The values marked with 'X' must be reached.
--echo # Poll till the select of connection user1 is blocked by the write lock on t1.
let $wait_condition= SELECT COUNT(*) = 1 FROM information_schema.processlist
WHERE state = "Table Lock"
  AND info = '$select_for_qc';
--source include/wait_condition.inc
eval
SELECT user,command,state,info FROM information_schema.processlist
WHERE state = "Table Lock"
  AND info = '$select_for_qc';
INSERT INTO t1 VALUES (4);

--echo # Switch to connection user2
connection user2;
UNLOCK TABLES;

--echo # Switch to connection user1
connection user1;
#
# Since the lock ordering rule in thr_multi_lock depends on
# pointer values, from execution to execution we might have
# different lock order, and therefore, sometimes lock t1 and block
# on t2, and sometimes block on t2 right away. In the second case,
# the following insert succeeds, and only then this select can
# proceed, and we actually test nothing, as the very first select
# returns 4 rows right away.
# It's fine to have a test case that covers the problematic area
# at least once in a while.
--echo # Collecting ("reap") the result from the previously blocked select.
--echo # The printing of the result (varies between 3 and 4 rows) set has to be suppressed.
--disable_result_log
--reap
--enable_result_log

--echo # Switch to connection user3
connection user3;
--echo # The next select enforces that effects of "concurrent_inserts" like the
--echo # record with a = 4 is missing in result sets can no more happen.
SELECT 1 FROM t1 WHERE a = 4;

--echo # Switch to connection user1
connection user1;
--echo # The next result set must contain 4 rows.
# If not, we have a regression of Bug#28249
eval $select_for_qc;
RESET QUERY CACHE;
eval $select_for_qc;

DROP TABLE t1,t2;

--echo # Switch to connection default + close connections user1,user2,user3
connection default;
disconnect user1;
disconnect user2;
disconnect user3;

SET GLOBAL query_cache_type=         @query_cache_type;
SET GLOBAL query_cache_limit=        @query_cache_limit;
SET GLOBAL query_cache_min_res_unit= @query_cache_min_res_unit;
SET GLOBAL query_cache_size=         @query_cache_size;