Bug#21828321: JSON FUNCS CALL DBUG_ABORT OR EXIT() ON WINDOWS!

If LEAST or GREATEST is called with only JSON arguments, and the
result of the call is passed as an argument to a JSON function, an
error is raised in release builds and an assert failure in debug
builds.

The LEAST and GREATEST functions don't have any special handling of
JSON values currently. JSON arguments are handled as if they were
strings, and the result is returned as a string. If all the arguments
have type JSON, however, the return type of the function will be set
to MYSQL_TYPE_JSON. If the result is passed as an argument to a JSON
function, the JSON function will attempt to call val_json() on the
result, since it appears to be a JSON value. Since the corresponding
Item subclass (Item_func_min_max) does not override Item::val_json(),
an error or assert failure is raised when val_json() is called.

The fix changes the return type of the function call from JSON to
string in the case where all arguments are JSON values. This way, the
receiving JSON function is not led to believe it's a JSON value and
does not call val_json() on it.

This patch also makes LEAST and GREATEST raise a "not supported yet"
warning if one of the arguments is JSON. This is meant as a
notification that these operators have not yet been updated to use the
JSON comparator, and may therefore give other results than expected.

The warning is raised by BETWEEN and IN as well, since those operators
also haven't been updated to use the JSON comparator to compare JSON
values.

Author: kahatlen

mysql-test/r/json.result

@@ -280,6 +280,8 @@ i	c1	c2	c3	c4	c5	c6	c7	c8	c9	c10	c11	c12	c13	c14	c15	c16	c17	c18	c19
 31	0	0	0	0	NULL	NULL	0	0	0	0	0	NULL	NULL	0	0	0	0	0	NULL
 100	0	0	0	1	NULL	NULL	0	0	0	0	0	NULL	NULL	0	0	0	0	0	NULL
 Warnings:
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the IN operator'
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the IN operator'
 Warning	3156	Invalid JSON value for CAST to DOUBLE: '{"a": 2}' from j at row 2
 Warning	3156	Invalid JSON value for CAST to DOUBLE: '[1, 2]' from j at row 35
 Warning	3156	Invalid JSON value for CAST to DOUBLE: '{"a": "b", "c": "d", "ab": "abc", "bc": ["x", "y"]}' from j at row 36
@@ -10978,6 +10980,8 @@ insert into tt(j) values (cast(1 as json)), (null);
 select sum( distinct j ) from tt group by j having j in ( avg( 1 ), 1 + j);
 sum( distinct j )
 1
+Warnings:
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the IN operator'
 SELECT JSON_ARRAY(j), COUNT(*) FROM tt GROUP BY j, i WITH ROLLUP;
 JSON_ARRAY(j)	COUNT(*)
 [null]	1
@@ -13387,3 +13391,16 @@ id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered
 Warnings:
 Note	1003	/* select#1 */ select json_object('c',json_extract(`test`.`t1`.`f1`,'$.b')) AS `f2` from `test`.`t1` having (json_type(json_extract(`f2`,'$.c')) <> 'NULL')
 DROP TABLE t1;
+#
+# Bug#21828321: JSON FUNCS CALL DBUG_ABORT OR EXIT() ON WINDOWS!
+#
+SELECT JSON_ARRAY(LEAST(NULL, NULL), GREATEST(NULL, NULL), LEAST(j1, NULL),
+GREATEST(NULL, j2), LEAST(j1, j2), GREATEST(j1, j2)) AS j
+FROM (SELECT CAST('1' AS JSON) AS j1, CAST('2' AS JSON) AS j2) t;
+j
+[null, null, null, null, "1", "2"]
+Warnings:
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the LEAST and GREATEST operators'
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the LEAST and GREATEST operators'
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the LEAST and GREATEST operators'
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the LEAST and GREATEST operators'

mysql-test/r/json_index.result

@@ -100,10 +100,13 @@ f1
 "vbn"
 "vbn"
 "vbn"
+Warnings:
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the BETWEEN operator'
 explain select f1 from t1 where json_extract(f1,"$") between "v" and "z";
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	NULL	range	gc_idx	gc_idx	83	NULL	4	100.00	Using where
 Warnings:
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the BETWEEN operator'
 Note	1003	/* select#1 */ select `test`.`t1`.`f1` AS `f1` from `test`.`t1` where (`test`.`t1`.`gc` between 'v' and 'z')
 select f1 from t1 where gc in ("asd","asasas","asdf");
 f1
@@ -120,10 +123,13 @@ f1
 "asasas"
 "asd"
 "asdf"
+Warnings:
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the IN operator'
 explain select f1 from t1 where json_extract(f1,"$") in ("asd","asasas","asdf");
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	NULL	range	gc_idx	gc_idx	83	NULL	3	100.00	Using where
 Warnings:
+Warning	1235	This version of MySQL doesn't yet support 'comparison of JSON in the IN operator'
 Note	1003	/* select#1 */ select `test`.`t1`.`f1` AS `f1` from `test`.`t1` where (`test`.`t1`.`gc` in ('asd','asasas','asdf'))
 select f1 from t1 where json_unquote(json_extract(f1,"$"))="asd";
 f1

mysql-test/t/json.test

@@ -6132,6 +6132,17 @@ EXPLAIN
 
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#21828321: JSON FUNCS CALL DBUG_ABORT OR EXIT() ON WINDOWS!
+--echo #
+# LEAST and GREATEST treat JSON arguments as strings for now. They used to hit
+# an assertion if used in a JSON context and all arguments were JSON values, or
+# a mix of NULLs and JSON values.
+SELECT JSON_ARRAY(LEAST(NULL, NULL), GREATEST(NULL, NULL), LEAST(j1, NULL),
+                  GREATEST(NULL, j2), LEAST(j1, j2), GREATEST(j1, j2)) AS j
+FROM (SELECT CAST('1' AS JSON) AS j1, CAST('2' AS JSON) AS j2) t;
+
+
 # Local Variables:
 # mode: sql
 # sql-product: mysql

sql/item_cmpfunc.cc

@@ -2962,6 +2962,14 @@ void Item_func_between::fix_length_and_dec()
   */
   reject_geometry_args(arg_count, args, this);
 
+  /*
+    JSON values will be compared as strings, and not with the JSON
+    comparator as one might expect. Raise a warning if one of the
+    arguments is JSON.
+  */
+  unsupported_json_comparison(arg_count, args,
+                              "comparison of JSON in the BETWEEN operator");
+
   /*
     Detect the comparison of DATE/DATETIME items.
     At least one of items should be a DATE/DATETIME item and other items
@@ -5305,6 +5313,16 @@ void Item_func_in::fix_length_and_dec()
       bisection_possible= false;
   }
 
+  /*
+    JSON values will be compared as strings, and not with the JSON
+    comparator as one might expect. Raise a warning if one of the
+    arguments is JSON. (The degenerate case x IN (y) may get rewritten
+    to x = y, though, and then the JSON comparator will be used if one
+    of the arguments is JSON.)
+  */
+  unsupported_json_comparison(arg_count, args,
+                              "comparison of JSON in the IN operator");
+
   if (type_cnt == 1)
   {
     if (cmp_type == STRING_RESULT && 

sql/item_func.cc

@@ -1266,6 +1266,35 @@ void reject_geometry_args(uint arg_count, Item **args, Item_result_field *me)
 }
 
 
+/**
+  Go through the arguments of a function and check if any of them are
+  JSON. If a JSON argument is found, raise a warning saying that this
+  operation is not supported yet. This function is used to notify
+  users that they are comparing JSON values using a mechanism that has
+  not yet been updated to use the JSON comparator. JSON values are
+  typically handled as strings in that case.
+
+  @param arg_count  the number of arguments
+  @param args       the arguments to go through looking for JSON values
+  @param msg        the message that explains what is not supported
+*/
+void unsupported_json_comparison(size_t arg_count, Item **args, const char *msg)
+{
+  for (size_t i= 0; i < arg_count; ++i)
+  {
+    if (args[i]->result_type() == STRING_RESULT &&
+        args[i]->field_type() == MYSQL_TYPE_JSON)
+    {
+      push_warning_printf(current_thd, Sql_condition::SL_WARNING,
+                          ER_NOT_SUPPORTED_YET,
+                          ER_THD(current_thd, ER_NOT_SUPPORTED_YET),
+                          msg);
+      break;
+    }
+  }
+}
+
+
 void Item_func_numhybrid::fix_length_and_dec()
 {
   fix_num_length_and_dec();
@@ -3496,6 +3525,18 @@ void Item_func_min_max::fix_length_and_dec()
   else if (cmp_type == REAL_RESULT)
     fix_char_length(float_length(decimals));
   cached_field_type= agg_field_type(args, arg_count);
+  /*
+    LEAST and GREATEST convert JSON values to strings before they are
+    compared, so their JSON nature is lost. Raise a warning to
+    indicate to the users that the values are not compared using the
+    JSON comparator, as they might expect. Also update the field type
+    of the result to reflect that the result is a string.
+  */
+  unsupported_json_comparison(arg_count, args,
+                              "comparison of JSON in the "
+                              "LEAST and GREATEST operators");
+  if (cached_field_type == MYSQL_TYPE_JSON)
+    cached_field_type= MYSQL_TYPE_VARCHAR;
   reject_geometry_args(arg_count, args, this);
 }
 

sql/item_func.h

@@ -28,7 +28,8 @@ class PT_item_list;
 
 extern void reject_geometry_args(uint arg_count, Item **args,
                                  Item_result_field *me);
-
+void unsupported_json_comparison(size_t arg_count, Item **args,
+                                 const char *msg);
 
 class Item_func :public Item_result_field
 {