From 56145be2951e0085848187bf6df8a0269e53fc7a Mon Sep 17 00:00:00 2001
From: Alexander Barkov <bar@mariadb.com>
Date: Wed, 27 Jun 2018 12:53:49 +0400
Subject: MDEV-16584 SP with a cursor inside a loop wastes THD memory
aggressively
Problem:
push_cursor() created sp_cursor instances on THD::main_mem_root,
which is freed only after the SP instructions loop.
Changes:
- Moving sp_cursor declaration from sp_rcontext.h to sql_class.h
- Deriving sp_instr_cpush from sp_cursor. So now sp_cursor is created
only once (at the SP parse time) and then reused on all loop iterations
- Adding a new method reset() into sp_cursor (and its parent classes)
to reset an sp_cursor instance before reuse.
- Moving former sp_cursor members m_fetch_count, m_row_count, m_found
into a separate class sp_cursor_statistics. This helps to reuse
the code in sp_cursor constructors, and in sp_cursor::reset()
- Adding a helper method sp_rcontext::pop_cursor().
- Adding "THD*" parameter to so_rcontext::pop_cursors() and pop_all_cursors()
- Removing "new" and "delete" from sp_rcontext::push_cursor() and
sp_rconext::pop_cursor().
- Fixing sp_cursor not to derive from Sql_alloc, as it's now allocated
only as a part of sp_instr_cpush (and not allocated separately).
- Moving lex_keeper->disable_query_cache() from sp_cursor::sp_cursor()
to sp_instr_cpush::execute().
- Adding tests
---
sql/sp_head.cc | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
(limited to 'sql/sp_head.cc')
diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index 40e5a71de21..6b116cb4550 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -1406,7 +1406,7 @@ sp_head::execute(THD *thd, bool merge_da_on_success)
/* Only pop cursors when we're done with group aggregate running. */
if (m_chistics.agg_type != GROUP_AGGREGATE ||
(m_chistics.agg_type == GROUP_AGGREGATE && thd->spcont->quit_func))
- thd->spcont->pop_all_cursors(); // To avoid memory leaks after an error
+ thd->spcont->pop_all_cursors(thd); // To avoid memory leaks after an error
/* Restore all saved */
if (m_chistics.agg_type == GROUP_AGGREGATE)
@@ -4186,11 +4186,13 @@ sp_instr_cpush::execute(THD *thd, uint *nextp)
{
DBUG_ENTER("sp_instr_cpush::execute");
- int ret= thd->spcont->push_cursor(thd, &m_lex_keeper);
+ sp_cursor::reset(thd, &m_lex_keeper);
+ m_lex_keeper.disable_query_cache();
+ thd->spcont->push_cursor(this);
*nextp= m_ip+1;
- DBUG_RETURN(ret);
+ DBUG_RETURN(false);
}
@@ -4224,7 +4226,7 @@ int
sp_instr_cpop::execute(THD *thd, uint *nextp)
{
DBUG_ENTER("sp_instr_cpop::execute");
- thd->spcont->pop_cursors(m_count);
+ thd->spcont->pop_cursors(thd, m_count);
*nextp= m_ip+1;
DBUG_RETURN(0);
}
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