refs codership/mysql-wsrep#201

- Fixes query cache so that it is aware of wsrep_sync_wait.
  Query cache would return (possibly stale) results to the
  client, regardless of the value of wsrep_sync_wait.
- Includes the test case that reproduced the issue.

5 files changed, 39 insertions, 7 deletions

diff --git a/sql/sql_cache.cc b/sql/sql_cache.cc
index e1efb1e85d6..0d3497ad964 100644
--- a/sql/sql_cache.cc
+++ b/sql/sql_cache.cc
@@ -1846,6 +1846,7 @@ Query_cache::send_result_to_client(THD *thd, char *org_sql, uint query_length)
       goto err;
     }
   }
+
   /*
     Try to obtain an exclusive lock on the query cache. If the cache is
     disabled or if a full cache flush is in progress, the attempt to
@@ -1957,6 +1958,25 @@ def_week_frmt: %lu, in_trans: %d, autocommit: %d",
   }
   DBUG_PRINT("qcache", ("Query in query hash 0x%lx", (ulong)query_block));
 
+#ifdef WITH_WSREP
+  if (WSREP_CLIENT(thd) && wsrep_must_sync_wait(thd)) {
+    unlock();
+    if (wsrep_sync_wait(thd))
+      goto err;
+    if (try_lock(TRUE))
+      goto err;
+    query_block = (Query_cache_block *) my_hash_search(&queries,
+                                                       (uchar*) sql,
+                                                       tot_length);
+    if (query_block == 0 ||
+        query_block->query()->result() == 0 ||
+        query_block->query()->result()->type != Query_cache_block::RESULT)
+    {
+      goto err_unlock;
+    }
+  }
+#endif /* WITH_WSREP */
+
   /* Now lock and test that nothing changed while blocks was unlocked */
   BLOCK_LOCK_RD(query_block);
 
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 7705ac45ffa..fa26494f35b 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -1213,6 +1213,7 @@ THD::THD()
   wsrep_mysql_replicated  = 0;
   wsrep_TOI_pre_query     = NULL;
   wsrep_TOI_pre_query_len = 0;
+  wsrep_sync_wait_gtid= WSREP_GTID_UNDEFINED;
 #endif
   /* Call to init() below requires fully initialized Open_tables_state. */
   reset_open_tables_state(this);
@@ -1628,6 +1629,7 @@ void THD::init(void)
   wsrep_mysql_replicated  = 0;
   wsrep_TOI_pre_query     = NULL;
   wsrep_TOI_pre_query_len = 0;
+  wsrep_sync_wait_gtid= WSREP_GTID_UNDEFINED;
 
   /*
     @@wsrep_causal_reads is now being handled via wsrep_sync_wait, update it
@@ -2361,6 +2363,10 @@ void THD::cleanup_after_query()
     rgi_slave->cleanup_after_query();
 #endif
 
+#ifdef WITH_WSREP
+  wsrep_sync_wait_gtid= WSREP_GTID_UNDEFINED;
+#endif /* WITH_WSREP */
+
   DBUG_VOID_RETURN;
 }
 
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 431edc3b38c..aee4d1dc359 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -2787,7 +2787,6 @@ public:
     query_id_t first_query_id;
   } binlog_evt_union;
 
-
   /**
     Internal parser state.
     Note that since the parser is not re-entrant, we keep only one parser
@@ -3865,6 +3864,7 @@ public:
   void*                     wsrep_apply_format;
   bool                      wsrep_apply_toi; /* applier processing in TOI */
   bool                      wsrep_skip_append_keys;
+  wsrep_gtid_t              wsrep_sync_wait_gtid;
 #endif /* WITH_WSREP */
 };
 
diff --git a/sql/wsrep_mysqld.cc b/sql/wsrep_mysqld.cc
index e622389de7e..0dd5c4dba14 100644
--- a/sql/wsrep_mysqld.cc
+++ b/sql/wsrep_mysqld.cc
@@ -810,19 +810,24 @@ bool wsrep_start_replication()
   return true;
 }
 
+bool wsrep_must_sync_wait (THD* thd, uint mask)
+{
+  return (thd->variables.wsrep_sync_wait & mask) &&
+    thd->variables.wsrep_on &&
+    !thd->in_active_multi_stmt_transaction() &&
+    thd->wsrep_conflict_state != REPLAYING &&
+    thd->wsrep_sync_wait_gtid.seqno == WSREP_SEQNO_UNDEFINED;
+}
+
 bool wsrep_sync_wait (THD* thd, uint mask)
 {
-  if ((thd->variables.wsrep_sync_wait & mask) &&
-      thd->variables.wsrep_on &&
-      !thd->in_active_multi_stmt_transaction() &&
-      thd->wsrep_conflict_state != REPLAYING)
+  if (wsrep_must_sync_wait(thd, mask))
   {
     WSREP_DEBUG("wsrep_sync_wait: thd->variables.wsrep_sync_wait = %u, mask = %u",
                 thd->variables.wsrep_sync_wait, mask);
     // This allows autocommit SELECTs and a first SELECT after SET AUTOCOMMIT=0
     // TODO: modify to check if thd has locked any rows.
-    wsrep_gtid_t  gtid;
-    wsrep_status_t ret= wsrep->causal_read (wsrep, &gtid);
+    wsrep_status_t ret= wsrep->causal_read (wsrep, &thd->wsrep_sync_wait_gtid);
 
     if (unlikely(WSREP_OK != ret))
     {
diff --git a/sql/wsrep_mysqld.h b/sql/wsrep_mysqld.h
index 1616bab695e..242227fd2a0 100644
--- a/sql/wsrep_mysqld.h
+++ b/sql/wsrep_mysqld.h
@@ -192,6 +192,7 @@ extern void wsrep_kill_mysql(THD *thd);
 /* new defines */
 extern void wsrep_stop_replication(THD *thd);
 extern bool wsrep_start_replication();
+extern bool wsrep_must_sync_wait (THD* thd, uint mask = WSREP_SYNC_WAIT_BEFORE_READ);
 extern bool wsrep_sync_wait (THD* thd, uint mask = WSREP_SYNC_WAIT_BEFORE_READ);
 extern int  wsrep_check_opts (int argc, char* const* argv);
 extern void wsrep_prepend_PATH (const char* path);