WL#2269 Enable query cache for NDB

- Added a thread that fetches commit_count for open tables. This
will mean that NDB will not have to be contacted for every use of a cached query. 


sql/ha_ndbcluster.cc:
  Added a thread that periodically will fetch commit_count 
  for open tables and store that value in share. 
  The commit count value is then used when query cache 
  asks if a cached query can be used. 
  The thread activation interval is regulated by the 
  config variable ndb_cache_check_time, it's default value is 0
  which means that NDB is contacted every time a cached query is reused.
sql/ha_ndbcluster.h:
  Added commit_count to share
  Added ndb_cache_check_time
sql/mysqld.cc:
  Added config variable ndb_cache_check_time
sql/set_var.cc:
  Added config variable ndb_cache_check_time

1 files changed, 193 insertions, 0 deletions

diff --git a/mysql-test/r/ndb_cache2.result b/mysql-test/r/ndb_cache2.result
new file mode 100644
index 00000000000..ce10e9dab00
--- /dev/null
+++ b/mysql-test/r/ndb_cache2.result
@@ -0,0 +1,193 @@
+drop table if exists t1;
+set GLOBAL query_cache_type=on;
+set GLOBAL query_cache_size=1355776;
+set GLOBAL ndb_cache_check_time=5;
+reset query cache;
+flush status;
+CREATE TABLE t1 ( pk int not null primary key,
+a int, b int not null, c varchar(20)) ENGINE=ndbcluster;
+insert into t1 value (1, 2, 3, 'First row');
+select * from t1;
+pk	a	b	c
+1	2	3	First row
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	1
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	1
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	0
+select * from t1;
+pk	a	b	c
+1	2	3	First row
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	1
+update t1 set a=3 where pk=1;
+select * from t1;
+pk	a	b	c
+1	3	3	First row
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	2
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	1
+insert into t1 value (2, 7, 8, 'Second row');
+insert into t1 value (4, 5, 6, 'Fourth row');
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+4	5	6	Fourth row
+1	3	3	First row
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	3
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	1
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+4	5	6	Fourth row
+1	3	3	First row
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	2
+select * from t1 where b=3;
+pk	a	b	c
+1	3	3	First row
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	2
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	2
+select * from t1 where b=3;
+pk	a	b	c
+1	3	3	First row
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	3
+delete from t1 where c='Fourth row';
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	0
+select * from t1 where b=3;
+pk	a	b	c
+1	3	3	First row
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	3
+use test;
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+1	3	3	First row
+select * from t1 where b=3;
+pk	a	b	c
+1	3	3	First row
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	4
+update t1 set a=4 where b=3;
+use test;
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	0
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+1	4	3	First row
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+1	4	3	First row
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	7
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	5
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+1	4	3	First row
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+1	4	3	First row
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	1
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	7
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	7
+begin;
+update t1 set a=5 where pk=1;
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	0
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	7
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	7
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+1	4	3	First row
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	1
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	8
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	7
+commit;
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	1
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	8
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	7
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+1	5	3	First row
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	9
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	7
+select * from t1;
+pk	a	b	c
+2	7	8	Second row
+1	5	3	First row
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	1
+show status like "Qcache_inserts";
+Variable_name	Value
+Qcache_inserts	9
+show status like "Qcache_hits";
+Variable_name	Value
+Qcache_hits	8
+drop table t1;
+show status like "Qcache_queries_in_cache";
+Variable_name	Value
+Qcache_queries_in_cache	0
+SET GLOBAL query_cache_size=0;
+SET GLOBAL ndb_cache_check_time=0;