From 665045f985787d77318a17ccddd67ec3ff92f7bc Mon Sep 17 00:00:00 2001
From: Igor Babaev <igor@askmonty.org>
Date: Mon, 21 Nov 2016 10:33:06 -0800
Subject: [PATCH] Fixed bug mdev-11081.
The idea of this fix was taken from the patch by Roy Lyseng
for mysql-5.6 bug iBug#14740889: "Wrong result for aggregate
functions when executing query through cursor".
Here's Roy's comment for his patch:
"
The problem was that a grouped query did not behave properly when
executed using a cursor. On further inspection, the query used one
intermediate temporary table for the grouping.
Then, Select_materialize::send_result_set_metadata created a temporary
table for storing the query result. Notice that get_unit_column_types()
is used to retrieve column meta-data for the query. The items contained
in this list are later modified so that their result_field points to
the row buffer of the materialized temporary table for the cursor.
But prior to this, these result_field objects have been prepared for
use in the grouping operation, by JOIN::make_tmp_tables_info(), hence
the grouping operation operates on wrong column buffers.
The problem is solved by using the list JOIN::fields when copying data
to the materialized table. This list is set by JOIN::make_tmp_tables_info()
and points to the columns of the last intermediate temporary table of
the executed query. For a UNION, it points to the temporary table
that is the result of the UNION query.
Notice that we have to assign a value to ::fields early in JOIN::optimize()
in case the optimization shortcuts due to a const plan detection.
A more optimal solution might be to avoid creating the final temporary
table when the query result is already stored in a temporary table.
"
The patch does not contain a test case, but the description of the
problem corresponds exactly what could be observed in the test
case for mdev-11081.
---
mysql-test/r/sp.result | 39 +++++++++++++++++++++++++++++++++++++++
mysql-test/t/sp.test | 38 ++++++++++++++++++++++++++++++++++++++
sql/item_subselect.cc | 2 +-
sql/sql_class.h | 2 +-
sql/sql_cursor.cc | 2 +-
sql/sql_lex.h | 2 +-
sql/sql_select.cc | 9 ++++++---
sql/sql_union.cc | 8 +++++---
8 files changed, 92 insertions(+), 10 deletions(-)
diff --git a/mysql-test/r/sp.result b/mysql-test/r/sp.result
index 130e789d3eb..aca9458f124 100644
--- a/mysql-test/r/sp.result
+++ b/mysql-test/r/sp.result
@@ -8001,3 +8001,42 @@ return 1;
end |
ERROR 0A000: Not allowed to return a result set from a function
drop table t1,t2;
+#
+# MDEV-11081: CURSOR for query with GROUP BY
+#
+CREATE TABLE t1 (name VARCHAR(10), value INT);
+INSERT INTO t1 VALUES ('b',1);
+INSERT INTO t1 VALUES ('b',1);
+INSERT INTO t1 VALUES ('c',1);
+INSERT INTO t1 VALUES ('a',1);
+INSERT INTO t1 VALUES ('a',1);
+INSERT INTO t1 VALUES ('a',1);
+CREATE PROCEDURE p1 ()
+BEGIN
+DECLARE done INT DEFAULT FALSE;
+DECLARE v_name VARCHAR(10);
+DECLARE v_total INT;
+DECLARE c CURSOR FOR
+SELECT name, SUM(value) AS total FROM t1 GROUP BY name;
+DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
+OPEN c;
+read_loop:
+LOOP
+FETCH c INTO v_name, v_total;
+IF done THEN
+LEAVE read_loop;
+END IF;
+SELECT v_name, v_total;
+END LOOP;
+CLOSE c;
+END;
+|
+CALL p1();
+v_name v_total
+a 3
+v_name v_total
+b 2
+v_name v_total
+c 1
+DROP PROCEDURE p1;
+DROP TABLE t1;
diff --git a/mysql-test/t/sp.test b/mysql-test/t/sp.test
index c80e1eaaa3e..aaab59bcb89 100644
--- a/mysql-test/t/sp.test
+++ b/mysql-test/t/sp.test
@@ -9446,3 +9446,41 @@ end |
--delimiter ;
drop table t1,t2;
+
+--echo #
+--echo # MDEV-11081: CURSOR for query with GROUP BY
+--echo #
+
+CREATE TABLE t1 (name VARCHAR(10), value INT);
+INSERT INTO t1 VALUES ('b',1);
+INSERT INTO t1 VALUES ('b',1);
+INSERT INTO t1 VALUES ('c',1);
+INSERT INTO t1 VALUES ('a',1);
+INSERT INTO t1 VALUES ('a',1);
+INSERT INTO t1 VALUES ('a',1);
+DELIMITER |;
+CREATE PROCEDURE p1 ()
+BEGIN
+ DECLARE done INT DEFAULT FALSE;
+ DECLARE v_name VARCHAR(10);
+ DECLARE v_total INT;
+ DECLARE c CURSOR FOR
+ SELECT name, SUM(value) AS total FROM t1 GROUP BY name;
+ DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
+ OPEN c;
+read_loop:
+ LOOP
+ FETCH c INTO v_name, v_total;
+ IF done THEN
+ LEAVE read_loop;
+ END IF;
+ SELECT v_name, v_total;
+ END LOOP;
+ CLOSE c;
+END;
+|
+DELIMITER ;|
+CALL p1();
+DROP PROCEDURE p1;
+DROP TABLE t1;
+
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index 21c633333f1..e90efbd82be 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -4572,7 +4572,7 @@ subselect_hash_sj_engine::get_strategy_using_schema()
return COMPLETE_MATCH;
else
{
- List_iterator<Item> inner_col_it(*item_in->unit->get_unit_column_types());
+ List_iterator<Item> inner_col_it(*item_in->unit->get_column_types(false));
Item *outer_col, *inner_col;
for (uint i= 0; i < item_in->left_expr->cols(); i++)
diff --git a/sql/sql_class.h b/sql/sql_class.h
index eeb6c917054..0434f5485cf 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -4392,7 +4392,7 @@ protected:
/*
All descendant classes have their send_data() skip the first
unit->offset_limit_cnt rows sent. Select_materialize
- also uses unit->get_unit_column_types().
+ also uses unit->get_column_types().
*/
SELECT_LEX_UNIT *unit;
/* Something used only by the parser: */
diff --git a/sql/sql_cursor.cc b/sql/sql_cursor.cc
index 7ecce8a8da3..118c6f23cb0 100644
--- a/sql/sql_cursor.cc
+++ b/sql/sql_cursor.cc
@@ -433,7 +433,7 @@ void Materialized_cursor::on_table_fill_finished()
bool Select_materialize::send_result_set_metadata(List<Item> &list, uint flags)
{
DBUG_ASSERT(table == 0);
- if (create_result_table(unit->thd, unit->get_unit_column_types(),
+ if (create_result_table(unit->thd, unit->get_column_types(true),
FALSE,
thd->variables.option_bits | TMP_TABLE_ALL_COLUMNS,
"", FALSE, TRUE, TRUE))
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index b044ef42b97..4a554ae7fe2 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -732,7 +732,7 @@ public:
friend void lex_start(THD *thd);
friend int subselect_union_engine::exec();
- List<Item> *get_unit_column_types();
+ List<Item> *get_column_types(bool for_cursor);
select_union *get_union_result() { return union_result; }
int save_union_explain(Explain_query *output);
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 1114e1e1f1d..168e0af5d38 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -1121,9 +1121,6 @@ int JOIN::optimize()
int
JOIN::optimize_inner()
{
-/*
- if (conds) { Item *it_clone= conds->build_clone(thd,thd->mem_root); }
-*/
ulonglong select_opts_for_readinfo;
uint no_jbuf_after;
JOIN_TAB *tab;
@@ -1137,6 +1134,12 @@ JOIN::optimize_inner()
set_allowed_join_cache_types();
need_distinct= TRUE;
+ /*
+ Needed in case optimizer short-cuts,
+ set properly in make_tmp_tables_info()
+ */
+ fields= &select_lex->item_list;
+
if (select_lex->first_cond_optimization)
{
//Do it only for the first execution
diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index 0d05d201f12..aad3701cca2 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -1382,7 +1382,9 @@ bool st_select_lex_unit::change_result(select_result_interceptor *new_result,
Get column type information for this unit.
SYNOPSIS
- st_select_lex_unit::get_unit_column_types()
+ st_select_lex_unit::get_column_types()
+ @param for_cursor if true return the list the fields
+ retrieved by the cursor
DESCRIPTION
For a single-select the column types are taken
@@ -1396,7 +1398,7 @@ bool st_select_lex_unit::change_result(select_result_interceptor *new_result,
st_select_lex_unit::prepare()
*/
-List<Item> *st_select_lex_unit::get_unit_column_types()
+List<Item> *st_select_lex_unit::get_column_types(bool for_cursor)
{
SELECT_LEX *sl= first_select();
bool is_procedure= MY_TEST(sl->join->procedure);
@@ -1416,7 +1418,7 @@ List<Item> *st_select_lex_unit::get_unit_column_types()
return &types;
}
- return &sl->item_list;
+ return for_cursor ? sl->join->fields : &sl->item_list;
}