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, 71 insertions, 0 deletions

diff --git a/mysql-test/t/ndb_cache_multi2.test b/mysql-test/t/ndb_cache_multi2.test
new file mode 100644
index 00000000000..a9d008dba7c
--- /dev/null
+++ b/mysql-test/t/ndb_cache_multi2.test
@@ -0,0 +1,71 @@
+-- source include/have_query_cache.inc
+-- source include/have_ndb.inc
+-- source include/have_multi_ndb.inc
+
+--disable_warnings
+drop table if exists t1, t2;
+--enable_warnings
+
+
+# Turn on and reset query cache on server1
+connection server1;
+set GLOBAL query_cache_type=on;
+set GLOBAL query_cache_size=1355776;
+set GLOBAL ndb_cache_check_time=1;
+reset query cache;
+flush status;
+
+# Turn on and reset query cache on server2
+connection server2;
+set GLOBAL query_cache_type=on;
+set GLOBAL query_cache_size=1355776;
+set GLOBAL ndb_cache_check_time=1;
+reset query cache;
+flush status;
+
+# Sleep so that the query cache check thread has time to start
+sleep 15;
+
+
+# Create test tables in NDB and load them into cache
+# on server1
+connection server1;
+create table t1 (a int) engine=ndbcluster;
+create table t2 (a int) engine=ndbcluster;
+insert into t1 value (2);
+insert into t2 value (3);
+select * from t1;
+select * from t2;
+show status like "Qcache_queries_in_cache";
+show status like "Qcache_inserts";
+show status like "Qcache_hits";
+
+
+# Connect server2, load table in to cache, then update the table
+connection server2;
+show status like "Qcache_queries_in_cache";
+show status like "Qcache_inserts";
+show status like "Qcache_hits";
+select * from t1;
+show status like "Qcache_queries_in_cache";
+show status like "Qcache_inserts";
+show status like "Qcache_hits";
+update t1 set a=3 where a=2;
+
+# Sleep so that the query cache check thread has time to run
+sleep 5;
+
+# Connect to server1 and check that cache is invalidated 
+# and correct data is returned
+connection server1;
+show status like "Qcache_queries_in_cache";
+show status like "Qcache_inserts";
+show status like "Qcache_hits";
+select * from t1;
+show status like "Qcache_queries_in_cache";
+show status like "Qcache_inserts";
+show status like "Qcache_hits";
+
+drop table t1, t2;
+
+