From 6facd4cb13170e8695d9ae4f1e30611af0b0a472 Mon Sep 17 00:00:00 2001 From: Alexander Nozdrin Date: Fri, 14 May 2010 22:11:25 +0400 Subject: Patch for Bug#27863 (excessive memory usage for many small queries in a multiquery packet). Background: - a query can contain multiple SQL statements; - the server frees resources allocated to process a query when the whole query is handled. In other words, resources allocated to process one SQL statement from a multi-statement query are freed when all SQL statements are handled. The problem was that the parser allocated a buffer of size of the whole query for each SQL statement in a multi-statement query. Thus, if a query had many SQL-statements (so, the query was long), but each SQL statement was short, ther parser tried to allocate huge amount of memory (number of small SQL statements * length of the whole query). The memory was allocated for a so-called "cpp buffer", which is intended to store pre-processed SQL statement -- SQL text without version specific comments. The fix is to allocate memory for the "cpp buffer" once for all SQL statements (once for a query). --- mysql-test/t/parser_stack.test | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'mysql-test/t/parser_stack.test') diff --git a/mysql-test/t/parser_stack.test b/mysql-test/t/parser_stack.test index 3330ef41833..bdcad5aa1b4 100644 --- a/mysql-test/t/parser_stack.test +++ b/mysql-test/t/parser_stack.test @@ -399,4 +399,12 @@ delimiter ;$$ drop procedure p_37228; +# +# Bug#27863 (excessive memory usage for many small queries in a multiquery +# packet). +# +let $i=`select repeat("set @a=1;", 65535)`; +--disable_query_log +eval $i; +--enable_query_log -- cgit v1.2.1