Fix for bug lp:1039277 "Crash in sql_cache.cc".

The crash happend when combining query cache, prepared statements and using a read only cursor.

sql/sql_cache.cc:
  Fixed unlikely error when one adjust query cache size in middle of operation
sql/sql_cursor.cc:
  Disable query cache when using cursors. This fixed lp:1039277
tests/mysql_client_test.c:
  Test case for lp:1039277

sql/sql_cache.cc

@@ -1813,7 +1813,10 @@ Query_cache::send_result_to_client(THD *thd, char *org_sql, uint query_length)
     goto err;
 
   if (query_cache_size == 0)
+  {
+    thd->query_cache_is_applicable= 0;            // Query can't be cached
     goto err_unlock;
+  }
 
   Query_cache_block *query_block;
   if (thd->variables.query_cache_strip_comments)

sql/sql_cursor.cc

@@ -115,6 +115,8 @@ int mysql_open_cursor(THD *thd, select_result *result,
                          &thd->security_ctx->priv_user[0],
                          (char *) thd->security_ctx->host_or_ip,
                          2);
+  /* Mark that we can't use query cache with cursors */
+  thd->query_cache_is_applicable= 0;
   rc= mysql_execute_command(thd);
   MYSQL_QUERY_EXEC_DONE(rc);
 

tests/mysql_client_test.c

@@ -357,6 +357,7 @@ static void test_prepare_insert_update()
   myquery(rc);
 }
 
+
 /* Test simple prepares of all DML statements */
 
 static void test_prepare_simple()
@@ -2308,6 +2309,7 @@ static void test_ps_query_cache()
 
       if (!opt_silent)
         fprintf(stdout, "OK");
+      break;
     }
 
     strmov(query, "select id1, value1 from t1 where id1= ? or "
@@ -13024,6 +13026,49 @@ static void test_bug8880()
     mysql_stmt_close(*stmt);
 }
 
+/*
+  Test executing a query with prepared statements while query cache is active
+*/
+
+static void test_open_cursor_prepared_statement_query_cache()
+{
+  MYSQL_STMT *stmt;
+  int rc;
+  MYSQL_RES *result;
+
+  myheader("test_open_cursor_prepared_statement_query_cache");
+  if (! is_query_cache_available())
+  {
+    fprintf(stdout, "Skipping test_open_cursor_prepared_statement_query_cache: Query cache not available.\n");
+    return;
+  }
+
+  rc= mysql_query(mysql, "set global query_cache_size=1000000");
+  myquery(rc);
+
+  mysql_query(mysql, "drop table if exists t1");
+  mysql_query(mysql, "create table t1 (a int not null primary key, b int)");
+  rc= mysql_query(mysql, "insert into t1 values (1,1)");
+  myquery(rc);                                  /* one check is enough */
+
+  /* Store query in query cache */
+  rc= mysql_query(mysql, "SELECT * FROM t1");
+  myquery(rc);
+  result= mysql_store_result(mysql);
+  mytest(result);
+  (void) my_process_result_set(result);
+  mysql_free_result(result);
+
+  /* Test using a cursor */
+  stmt= open_cursor("select a from t1");
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+  mysql_stmt_close(stmt);
+
+  rc= mysql_query(mysql, "set global query_cache_size=1000000");
+  myquery(rc);
+}
+
 
 static void test_bug9159()
 {
@@ -18917,6 +18962,8 @@ static struct my_tests_st my_tests[]= {
   { "test_bug8378", test_bug8378 },
   { "test_bug8722", test_bug8722 },
   { "test_bug8880", test_bug8880 },
+  { "test_open_cursor_prepared_statement_query_cache",
+    test_open_cursor_prepared_statement_query_cache },
   { "test_bug9159", test_bug9159 },
   { "test_bug9520", test_bug9520 },
   { "test_bug9478", test_bug9478 },