MDEV-23388 Assertion `args[0]->decimals == 0' failed in Item_func_round::fix_arg_int

Type_handler_temporal_result::Item_func_min_max_fix_attributes() in an expression GREATEST(string,date), e.g: SELECT GREATEST('1', CAST('2020-12-12' AS DATE)); incorrectly evaluated decimals as 6 (like for DATETIME). Adding a separate virtual implementation: Type_handler_date_common::Item_func_min_max_fix_attributes() This makes the code simpler.

Author: abarkov

mysql-test/main/type_date.result

@@ -1103,5 +1103,35 @@ t2	CREATE TABLE `t2` (
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 DROP TABLE t2,t1;
 #
+# MDEV-23388 Assertion `args[0]->decimals == 0' failed in Item_func_round::fix_arg_int
+#
+SELECT ROUND(GREATEST('1', CAST('2020-12-12' AS DATE)));
+ROUND(GREATEST('1', CAST('2020-12-12' AS DATE)))
+20201212
+Warnings:
+Warning	1292	Truncated incorrect datetime value: '1'
+SELECT GREATEST('1', CAST('2020-12-12' AS DATE));
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def	GREATEST('1', CAST('2020-12-12' AS DATE))	10	10	10	Y	128	0	63
+GREATEST('1', CAST('2020-12-12' AS DATE))
+2020-12-12
+Warnings:
+Warning	1292	Truncated incorrect datetime value: '1'
+CREATE TABLE t1 (c_date DATE NOT NULL, c_int INT NOT NULL);
+CREATE TABLE t2 AS SELECT
+GREATEST(c_date,c_date),
+GREATEST(c_date,c_int),
+GREATEST(c_int,c_date)
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+ `GREATEST(c_date,c_date)` date NOT NULL,
+ `GREATEST(c_date,c_int)` date DEFAULT NULL,
+ `GREATEST(c_int,c_date)` date DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t2;
+DROP TABLE t1;
+#
 # End of 10.4 tests
 #

mysql-test/main/type_date.test

@@ -749,6 +749,28 @@ CREATE TABLE t2 AS SELECT FLOOR(a), CEIL(a),ROUND(a),TRUNCATE(a,0) FROM t1;
 SHOW CREATE TABLE t2;
 DROP TABLE t2,t1;
 
+--echo #
+--echo # MDEV-23388 Assertion `args[0]->decimals == 0' failed in Item_func_round::fix_arg_int
+--echo #
+
+SELECT ROUND(GREATEST('1', CAST('2020-12-12' AS DATE)));
+
+--disable_ps_protocol
+--enable_metadata
+SELECT GREATEST('1', CAST('2020-12-12' AS DATE));
+--disable_metadata
+--enable_ps_protocol
+
+CREATE TABLE t1 (c_date DATE NOT NULL, c_int INT NOT NULL);
+CREATE TABLE t2 AS SELECT
+ GREATEST(c_date,c_date),
+ GREATEST(c_date,c_int),
+ GREATEST(c_int,c_date)
+FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t2;
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.4 tests
 --echo #

sql/sql_type.cc

@@ -4120,6 +4120,7 @@ bool Type_handler_temporal_result::
  Item_func_min_max_fix_attributes(THD *thd, Item_func_min_max *func,
  Item **items, uint nitems) const
 {
+ DBUG_ASSERT(func->field_type() != MYSQL_TYPE_DATE);
  bool rc= Type_handler::Item_func_min_max_fix_attributes(thd, func,
  items, nitems);
  bool is_time= func->field_type() == MYSQL_TYPE_TIME;
@@ -4174,7 +4175,6 @@ bool Type_handler_temporal_result::
  DATETIME DATETIME no conversion
  DATETIME TIMESTAMP safe conversion
  DATETIME DATE safe conversion
- DATE DATE no conversion
  TIME TIME no conversion
 
  Note, a function cannot return TIMESTAMP if it has non-TIMESTAMP
@@ -4191,9 +4191,6 @@ bool Type_handler_temporal_result::
  -------------------- ------------- -------
  TIMESTAMP TIME Not possible
  DATETIME TIME depends on OLD_MODE_ZERO_DATE_TIME_CAST
- DATE TIMESTAMP Not possible
- DATE DATETIME Not possible
- DATE TIME Not possible
  TIME TIMESTAMP Not possible
  TIME DATETIME Not possible
  TIME DATE Not possible
@@ -4216,6 +4213,30 @@ bool Type_handler_temporal_result::
 }
 
 
+bool Type_handler_date_common::
+ Item_func_min_max_fix_attributes(THD *thd, Item_func_min_max *func,
+ Item **items, uint nitems) const
+{
+ func->fix_attributes_date();
+ if (func->maybe_null)
+ return false;
+ /*
+ We cannot trust the generic maybe_null value calculated during fix_fields().
+ If a conversion from non-temoral types to DATE happens,
+ then the result can be NULL (even if all arguments are not NULL).
+ */
+ for (uint i= 0; i < nitems; i++)
+ {
+ if (items[i]->type_handler()->cmp_type() != TIME_RESULT)
+ {
+ func->maybe_null= true;
+ break;
+ }
+ }
+ return false;
+}
+
+
 bool Type_handler_real_result::
  Item_func_min_max_fix_attributes(THD *thd, Item_func_min_max *func,
  Item **items, uint nitems) const

sql/sql_type.h

@@ -5508,6 +5508,8 @@ class Type_handler_date_common: public Type_handler_temporal_with_date
  Type_handler_hybrid_field_type *,
  Type_all_attributes *atrr,
  Item **items, uint nitems) const;
+ bool Item_func_min_max_fix_attributes(THD *thd, Item_func_min_max *func,
+ Item **items, uint nitems) const;
  void Item_param_set_param_func(Item_param *param,
  uchar **pos, ulong len) const;
 };