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eaf7728d9f
Cache".
WL#1569 "Prepared Statements: implement support of Query Cache".
Prepared SELECTs did not look up in the query cache, and their results
were not stored in the query cache. This made them slower than
non-prepared SELECTs in some cases.
The fix is to re-use the expanded query (the prepared query where
"?" placeholders are replaced by their values, at execution time)
for searching/storing in the query cache.
It works fine for statements prepared via mysql_stmt_prepare(), which
are the most commonly used and were the scope of this bugfix and WL.
It works less fine for statements prepared via the SQL command
PREPARE...FROM, which are still not using the query cache if they
have at least one parameter (because then the expanded query contains
names of user variables, and user variables don't work with the
query cache, even in non-prepared queries).
Note that results from prepared SELECTs, which are in the binary
protocol, and results from normal SELECTs, which are in the text
protocol, ignore each other in the query cache, because a result in the
binary protocol should never be served to a SELECT expecting the text
protocol and vice-versa.
Note, after this patch, bug 25843 starts applying to query cache
("changing default database between PREPARE and EXECUTE of statement
breaks binlog"), we need to fix it.
126 lines
4.2 KiB
Text
126 lines
4.2 KiB
Text
-- source include/have_query_cache.inc
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-- source include/have_ndb.inc
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-- source include/have_multi_ndb.inc
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-- source include/not_embedded.inc
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--disable_warnings
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drop table if exists t1, t2;
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--enable_warnings
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# Turn on and reset query cache on server1
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connection server1;
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echo == Connected to server1 ==;
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set GLOBAL query_cache_type=on;
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set GLOBAL query_cache_size=1355776;
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set GLOBAL ndb_cache_check_time=1;
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reset query cache;
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flush status;
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# Turn on and reset query cache on server2
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connection server2;
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echo == Connected to server2 ==;
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set GLOBAL query_cache_type=on;
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set GLOBAL query_cache_size=1355776;
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set GLOBAL ndb_cache_check_time=1;
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reset query cache;
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flush status;
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# Create test tables in NDB and load them into cache
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# on server1
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connection server1;
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echo == Connected to server1 ==;
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create table t1 (a int) engine=ndbcluster;
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create table t2 (a int) engine=ndbcluster;
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insert into t1 value (2);
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insert into t2 value (3);
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select * from t1;
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# Run the check query once to load it into qc on server1
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# See at the end of this test why we need to disable ps-protocol for
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# this query (*)
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--disable_ps_protocol
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select a != 3 from t1;
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--enable_ps_protocol
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select * from t2;
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show status like "Qcache_queries_in_cache";
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show status like "Qcache_inserts";
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show status like "Qcache_hits";
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# Connect server2, load table in to cache, then update the table
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connection server2;
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echo == Connected to server2 ==;
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show status like "Qcache_queries_in_cache";
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show status like "Qcache_inserts";
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show status like "Qcache_hits";
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select * from t1;
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show status like "Qcache_queries_in_cache";
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show status like "Qcache_inserts";
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show status like "Qcache_hits";
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update t1 set a=3 where a=2;
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# Connect to server1 and check that cache is invalidated
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# and correct data is returned
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connection server1;
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echo == Connected to server1 ==;
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# Loop and wait for max 10 seconds until query cache thread
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# has invalidated the cache and the column a in t1 is equal to 3
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let $retries=20;
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while (`select a != 3 from t1`)
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{
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dec $retries;
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if (!$retries)
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{
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The query_cache thread failed to invalidate query_cache in 10 seconds;
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}
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sleep 0.5;
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}
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# Select from t1 one last time for the result file
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# Column a should be 3
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select * from t1;
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# There should now be three queries in the cache
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show status like "Qcache_queries_in_cache";
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drop table t1, t2;
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# Turn off and reset query cache on server1 and server2
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connection server1;
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set GLOBAL query_cache_size=0;
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set GLOBAL ndb_cache_check_time=0;
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reset query cache;
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flush status;
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connection server2;
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set GLOBAL query_cache_size=0;
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set GLOBAL ndb_cache_check_time=0;
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reset query cache;
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flush status;
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# (*) Why we need to execute the query in non-ps mode.
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# The principle of this test is: two mysqlds connected to one cluster,
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# both using their query cache. Queries are cached in server1
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# ("select a!=3 from t1", "select * from t1"),
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# table t1 is modified in server2, we want to see that this invalidates
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# the query cache of server1. Invalidation with NDB works like this:
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# when a query is found in the query cache, NDB is asked if the tables
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# have changed. In this test, ha_ndbcluster calls NDB every millisecond
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# to collect change information about tables.
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# Due to this millisecond delay, there is need for a loop ("while...")
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# in this test, which waits until a query1 ("select a!=3 from t1") is
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# invalidated (which is equivalent to it returning
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# up-to-date results), and then expects query2 ("select * from t1")
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# to have been invalidated (see up-to-date results).
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# But when enabling --ps-protocol in this test, the logic breaks,
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# because query1 is still done via mysql_real_query() (see mysqltest.c:
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# eval_expr() always uses mysql_real_query()). So, query1 returning
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# up-to-date results is not a sign of it being invalidated in the cache,
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# because it was NOT in the cache ("select a!=3 from t1" on line 39
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# was done with prep stmts, while `select a!=3 from t1` is not,
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# thus the second does not see the first in the cache). Thus, we may run
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# query2 when cache still has not been invalidated.
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# The solution is to make the initial "select a!=3 from t1" run
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# as a normal query, this repairs the broken logic.
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# But note, "select * from t1" is still using prepared statements
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# which was the goal of this test with --ps-protocol.
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