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Fix for bug#5400 "GROUP_CONCAT returns everything twice":

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Don't evaluate the value of GROUP_CONCAT several times for the same 'group', reuse the value instead.
This commit is contained in:
sergefp@mysql.com
2004-09-08 22:43:37 +04:00
parent 0afcaac5a8
commit c8422dfcc7
3 changed files with 20 additions and 0 deletions
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9
mysql-test/r/group_by.result
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@@ -629,3 +629,12 @@ explain SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL;
id select_type table type possible_keys key key_len ref rows Extra id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 6 Using filesort 1 SIMPLE t1 ALL NULL NULL NULL NULL 6 Using filesort
DROP TABLE t1; DROP TABLE t1;
create table t1 ( col1 int, col2 int );
insert into t1 values (1,1),(1,2),(1,3),(2,1),(2,2);
select group_concat( distinct col1 ) as alias from t1
group by col2 having alias like '%';
alias
1,2
1,2
1
drop table t1;

9
mysql-test/t/group_by.test
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@@ -456,3 +456,12 @@ INSERT INTO t1 VALUES (1,2),(2,3),(4,5),(3,5),(1,5),(23,5);
SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL; SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL;
explain SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL; explain SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL;
DROP TABLE t1; DROP TABLE t1;
# Test for BUG#5400: GROUP_CONCAT returns everything twice.
create table t1 ( col1 int, col2 int );
insert into t1 values (1,1),(1,2),(1,3),(2,1),(2,2);
select group_concat( distinct col1 ) as alias from t1
group by col2 having alias like '%';
drop table t1;

2
sql/item_sum.cc
View File

@@ -2121,6 +2121,8 @@ String* Item_func_group_concat::val_str(String* str)
DBUG_ASSERT(fixed == 1); DBUG_ASSERT(fixed == 1);
if (null_value) if (null_value)
return 0; return 0;
if (result.length())
return &result;
if (tree_mode) if (tree_mode)
{ {
tree_walk(tree, (tree_walk_action)&dump_leaf_key, (void*)this, tree_walk(tree, (tree_walk_action)&dump_leaf_key, (void*)this,