Fixed bug#13575: SP funcs in select with distinct/group and order by can

produce wrong data

By default Item_sp_func::val_str() returns string from it's result_field 
internal buffer. When grouping is present Item_copy_string is used to 
store SP function result, but it doesn't additionally buffer the result.
When the next record is read, internal buffer is overwritten, due to
this Item_copy_string::val_str() will have wrong data. Thus producing
weird query result.

The Item_func_sp::val_str() now makes a copy of returned value to prevent
occasional corruption.


mysql-test/t/sp.test:
  Added test case for bug#13575: SP funcs in select with distinct/group and order by can
  produce wrong data
mysql-test/r/sp.result:
  Added test case for bug#13575: SP funcs in select with distinct/group and
      order by can produce wrong data
sql/item_func.h:
  Fixed bug#13575: SP funcs in select with distinct/group and order by can
      produce wrong data
      The Item_func_sp::val_str() now makes a copy of returned value to prevent
      occasinal corruption.

1 files changed, 16 insertions, 0 deletions

diff --git a/mysql-test/r/sp.result b/mysql-test/r/sp.result
index 45e8e0ce55a..fd09e9c8e94 100644
--- a/mysql-test/r/sp.result
+++ b/mysql-test/r/sp.result
@@ -4786,4 +4786,20 @@ i
 0
 drop table t3|
 drop procedure bug16887|
+create table t3 (f1 int, f2 varchar(3), primary key(f1)) engine=innodb|
+insert into t3 values (1,'aaa'),(2,'bbb'),(3,'ccc')|
+CREATE FUNCTION bug13575 ( p1 integer ) 
+returns varchar(3) 
+BEGIN 
+DECLARE v1 VARCHAR(10) DEFAULT null;
+SELECT f2 INTO v1 FROM t3 WHERE f1 = p1; 
+RETURN v1;
+END|
+select distinct f1, bug13575(f1) from t3 order by f1|
+f1	bug13575(f1)
+1	aaa
+2	bbb
+3	ccc
+drop function bug13575;
+drop table t3|
 drop table t1,t2;