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Fix for BUG#735 "Prepared Statements: there is no support for Query

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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.
This commit is contained in:
guilhem@gbichot3.local
2007-03-09 18:09:57 +01:00
parent 8efe1b1fae
commit eaf7728d9f
13 changed files with 808 additions and 29 deletions
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20
sql/sql_cache.cc
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@@ -844,6 +844,12 @@ void Query_cache::store_query(THD *thd, TABLE_LIST *tables_used)
flags.client_long_flag= test(thd->client_capabilities & CLIENT_LONG_FLAG);
flags.client_protocol_41= test(thd->client_capabilities &
CLIENT_PROTOCOL_41);
/*
Protocol influences result format, so statement results in the binary
protocol (COM_EXECUTE) cannot be served to statements asking for results
in the text protocol (COM_QUERY) and vice-versa.
*/
flags.result_in_binary_protocol= (unsigned int) thd->protocol->type();
flags.more_results_exists= test(thd->server_status &
SERVER_MORE_RESULTS_EXISTS);
flags.pkt_nr= net->pkt_nr;
@@ -861,11 +867,13 @@ void Query_cache::store_query(THD *thd, TABLE_LIST *tables_used)
flags.max_sort_length= thd->variables.max_sort_length;
flags.lc_time_names= thd->variables.lc_time_names;
flags.group_concat_max_len= thd->variables.group_concat_max_len;
DBUG_PRINT("qcache", ("long %d, 4.1: %d, more results %d, pkt_nr: %d, \
DBUG_PRINT("qcache", ("\
long %d, 4.1: %d, bin_proto: %d, more results %d, pkt_nr: %d, \
CS client: %u, CS result: %u, CS conn: %u, limit: %lu, TZ: 0x%lx, \
sql mode: 0x%lx, sort len: %lu, conncat len: %lu",
(int)flags.client_long_flag,
(int)flags.client_protocol_41,
(int)flags.result_in_binary_protocol,
(int)flags.more_results_exists,
flags.pkt_nr,
flags.character_set_client_num,
@@ -1089,6 +1097,7 @@ Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length)
flags.client_long_flag= test(thd->client_capabilities & CLIENT_LONG_FLAG);
flags.client_protocol_41= test(thd->client_capabilities &
CLIENT_PROTOCOL_41);
flags.result_in_binary_protocol= (unsigned int)thd->protocol->type();
flags.more_results_exists= test(thd->server_status &
SERVER_MORE_RESULTS_EXISTS);
flags.pkt_nr= thd->net.pkt_nr;
@@ -1104,11 +1113,13 @@ Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length)
flags.max_sort_length= thd->variables.max_sort_length;
flags.group_concat_max_len= thd->variables.group_concat_max_len;
flags.lc_time_names= thd->variables.lc_time_names;
DBUG_PRINT("qcache", ("long %d, 4.1: %d, more results %d, pkt_nr: %d, \
DBUG_PRINT("qcache", ("\
long %d, 4.1: %d, bin_proto: %d, more results %d, pkt_nr: %d, \
CS client: %u, CS result: %u, CS conn: %u, limit: %lu, TZ: 0x%lx, \
sql mode: 0x%lx, sort len: %lu, conncat len: %lu",
(int)flags.client_long_flag,
(int)flags.client_protocol_41,
(int)flags.result_in_binary_protocol,
(int)flags.more_results_exists,
flags.pkt_nr,
flags.character_set_client_num,
@@ -3048,11 +3059,10 @@ Query_cache::is_cacheable(THD *thd, uint32 query_len, char *query, LEX *lex,
TABLE_COUNTER_TYPE table_count;
DBUG_ENTER("Query_cache::is_cacheable");
if (lex->sql_command == SQLCOM_SELECT &&
if (query_cache_is_cacheable_query(lex) &&
(thd->variables.query_cache_type == 1 ||
(thd->variables.query_cache_type == 2 && (lex->select_lex.options &
OPTION_TO_QUERY_CACHE))) &&
lex->safe_to_cache_query)
OPTION_TO_QUERY_CACHE))))
{
DBUG_PRINT("qcache", ("options: %lx %lx type: %u",
(long) OPTION_TO_QUERY_CACHE,