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MDEV-23029: JSON_OBJECTAGG returns NULL when used together with GROUP BY

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Quick grouping is not supported for JSON_OBJECTAGG. The same for GROUP_CONCAT too
so make sure that Item::quick_group is set to FALSE. We need to make sure that in
the case of JSON_OBJECTAGG we don't create an index over grouping fields of
the temp table and update the result after each iteration.
Instead we should first sort the result in accordance to the
GROUP BY fields and then perform the grouping and
write the result to the temp table.
This commit is contained in:
Varun Gupta
2020-06-29 20:06:28 +05:30
parent c687afbbde
commit 7e19954b9a
4 changed files with 28 additions and 0 deletions
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14
mysql-test/main/func_json.result
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@ -1328,5 +1328,19 @@ JSON_ARRAYAGG(col1)
[{"color":"red", "size":1},{"color":"blue", "size":2}] [{"color":"red", "size":1},{"color":"blue", "size":2}]
drop table t1; drop table t1;
# #
# MDEV-23029: JSON_OBJECTAGG returns NULL when used together with GROUP BY
#
CREATE TABLE t1 (e INT, a VARCHAR(255), v VARCHAR(255));
INSERT INTO t1 VALUES (0, 'a1', '1') , (0, 'a2', '2') , (1, 'b1', '3');
EXPLAIN SELECT B.e, JSON_OBJECTAGG(B.a, B.v) FROM t1 A, t1 B GROUP BY B.e;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE A ALL NULL NULL NULL NULL 3 Using temporary; Using filesort
1 SIMPLE B ALL NULL NULL NULL NULL 3 Using join buffer (flat, BNL join)
SELECT B.e, JSON_OBJECTAGG(B.a, B.v) FROM t1 A, t1 B GROUP BY B.e;
e JSON_OBJECTAGG(B.a, B.v)
0 {"a1":"1", "a1":"1", "a1":"1", "a2":"2", "a2":"2", "a2":"2"}
1 {"b1":"3", "b1":"3", "b1":"3"}
DROP TABLE t1;
#
# End of 10.5 tests # End of 10.5 tests
# #

12
mysql-test/main/func_json.test
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@ -826,6 +826,18 @@ insert into t1 values('{"color":"blue", "size":2}' );
select JSON_ARRAYAGG(col1) from t1; select JSON_ARRAYAGG(col1) from t1;
drop table t1; drop table t1;
--echo #
--echo # MDEV-23029: JSON_OBJECTAGG returns NULL when used together with GROUP BY
--echo #
CREATE TABLE t1 (e INT, a VARCHAR(255), v VARCHAR(255));
INSERT INTO t1 VALUES (0, 'a1', '1') , (0, 'a2', '2') , (1, 'b1', '3');
EXPLAIN SELECT B.e, JSON_OBJECTAGG(B.a, B.v) FROM t1 A, t1 B GROUP BY B.e;
SELECT B.e, JSON_OBJECTAGG(B.a, B.v) FROM t1 A, t1 B GROUP BY B.e;
DROP TABLE t1;
--echo # --echo #
--echo # End of 10.5 tests --echo # End of 10.5 tests
--echo # --echo #

1
sql/item_jsonfunc.cc
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@ -3725,6 +3725,7 @@ Item_func_json_objectagg::
Item_func_json_objectagg(THD *thd, Item_func_json_objectagg *item) Item_func_json_objectagg(THD *thd, Item_func_json_objectagg *item)
:Item_sum(thd, item) :Item_sum(thd, item)
{ {
quick_group= FALSE;
result.set_charset(collation.collation); result.set_charset(collation.collation);
result.append("{"); result.append("{");
} }

1
sql/item_jsonfunc.h
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@ -579,6 +579,7 @@ public:
Item_func_json_objectagg(THD *thd, Item *key, Item *value) : Item_func_json_objectagg(THD *thd, Item *key, Item *value) :
Item_sum(thd, key, value) Item_sum(thd, key, value)
{ {
quick_group= FALSE;
result.append("{"); result.append("{");
} }