Fixed that prepared statements are properly igored (if possible) by query cache.

sql/sql_cache.cc

@@ -1659,6 +1659,17 @@ Query_cache::send_result_to_client(THD *thd, char *org_sql, uint query_length)
   if (is_disabled() || thd->locked_tables ||
       thd->variables.query_cache_type == 0)
     goto err;
+
+  /*
+    The following can only happen for prepared statements that was found
+    during parsing or later that the query was not cacheable.
+  */
+  if (!thd->lex->safe_to_cache_query)
+  {
+    DBUG_PRINT("qcache", ("SELECT is non-cacheable"));
+    goto err;
+  }
+
   DBUG_ASSERT(query_cache_size != 0);           // otherwise cache would be disabled
 
   thd->query_cache_is_applicable= 1;
@@ -1950,6 +1961,7 @@ def_week_frmt: %lu, in_trans: %d, autocommit: %d",
           faster.
         */
         thd->query_cache_is_applicable= 0;      // Query can't be cached
+        thd->lex->safe_to_cache_query= 0;       // For prepared statements
         BLOCK_UNLOCK_RD(query_block);
         DBUG_RETURN(-1);
       }
@@ -1966,6 +1978,7 @@ def_week_frmt: %lu, in_trans: %d, autocommit: %d",
 		  table_list.db, table_list.alias));
       unlock();
       thd->query_cache_is_applicable= 0;        // Query can't be cached
+      thd->lex->safe_to_cache_query= 0;         // For prepared statements
       BLOCK_UNLOCK_RD(query_block);
       DBUG_RETURN(-1);				// Privilege error
     }
@@ -1975,6 +1988,7 @@ def_week_frmt: %lu, in_trans: %d, autocommit: %d",
 			    table_list.db, table_list.alias));
       BLOCK_UNLOCK_RD(query_block);
       thd->query_cache_is_applicable= 0;        // Query can't be cached
+      thd->lex->safe_to_cache_query= 0;         // For prepared statements
       goto err_unlock;				// Parse query
     }
 #endif /*!NO_EMBEDDED_ACCESS_CHECKS*/
@@ -1998,7 +2012,13 @@ def_week_frmt: %lu, in_trans: %d, autocommit: %d",
                                   table->key_length());
       }
       else
+      {
+        /*
+          As this can change from call to call, don't reset set
+          thd->lex->safe_to_cache_query
+        */
         thd->query_cache_is_applicable= 0;      // Query can't be cached
+      }
       goto err_unlock;				// Parse query
     }
     else
@@ -3886,6 +3906,7 @@ Query_cache::process_and_count_tables(THD *thd, TABLE_LIST *tables_used,
       DBUG_PRINT("qcache", ("Don't cache statement as it refers to "
                             "tables with column privileges."));
       thd->query_cache_is_applicable= 0;        // Query can't be cached
+      thd->lex->safe_to_cache_query= 0;         // For prepared statements
       DBUG_RETURN(0);
     }
 #endif
@@ -4022,6 +4043,10 @@ my_bool Query_cache::ask_handler_allowance(THD *thd,
     {
       DBUG_PRINT("qcache", ("Handler does not allow caching for %s.%s",
 			    tables_used->db, tables_used->alias));
+      /*
+        As this can change from call to call, don't reset set
+        thd->lex->safe_to_cache_query
+      */
       thd->query_cache_is_applicable= 0;        // Query can't be cached
       DBUG_RETURN(1);
     }