MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field

Disable IDENTITY_SUBST propagation for ZEROFILL columns,
as discussed with Sergei.

mysql-test/r/compare.result

@@ -64,7 +64,7 @@ EXPLAIN EXTENDED SELECT b,c FROM t1 WHERE b = 1 AND CONCAT(b,c) = '0101';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t1`.`c` AS `c` from `test`.`t1` where ((`test`.`t1`.`b` = 1) and (concat('01',`test`.`t1`.`c`) = '0101'))
+Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t1`.`c` AS `c` from `test`.`t1` where ((`test`.`t1`.`b` = 1) and (concat(`test`.`t1`.`b`,`test`.`t1`.`c`) = '0101'))
 SELECT b,c FROM t1 WHERE b = 1 AND CONCAT(b,c) = '0101';
 b	c
 01	01

mysql-test/r/func_encrypt.result

@@ -190,3 +190,21 @@ insert into t1 values (null,'contraction\'s');
 insert into t1 values (-15818,'requirement\'s');
 select encrypt(f1,f2) as a from t1,(select encrypt(f1,f2) as b from t1) a;
 drop table t1;
+#
+# Start of 10.1 tests
+#
+#
+# MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field
+#
+CREATE TABLE t1 (a INT(6) ZEROFILL);
+INSERT INTO t1 VALUES (1),(2);
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=1 AND DES_ENCRYPT('test',a)=_latin1 'abc' COLLATE latin1_bin;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 1) and (des_encrypt('test',`test`.`t1`.`a`) = 'abc'))
+DROP TABLE t1;
+#
+# End of 10.1 tests
+#

mysql-test/r/func_str.result

@@ -4535,3 +4535,30 @@ set global max_allowed_packet=default;
 #
 # End of 5.6 tests
 #
+#
+# Start of 10.1 tests
+#
+#
+# MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field
+#
+CREATE TABLE t1 (a BIGINT(20) ZEROFILL);
+INSERT INTO t1 VALUES (18446744073709551615),(0);
+SELECT * FROM t1 WHERE a=18446744073709551615;
+a
+18446744073709551615
+SELECT * FROM t1 WHERE FORMAT(a,0)='18,446,744,073,709,551,615';
+a
+18446744073709551615
+SELECT * FROM t1 WHERE a=18446744073709551615 AND FORMAT(a,0)='18,446,744,073,709,551,615';
+a
+18446744073709551615
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=18446744073709551615 AND FORMAT(a,0)='18,446,744,073,709,551,615';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 18446744073709551615) and (format(`test`.`t1`.`a`,0) = '18,446,744,073,709,551,615'))
+DROP TABLE t1;
+#
+# End of 10.1 tests
+#

mysql-test/r/func_weight_string.result

@@ -92,3 +92,51 @@ Warnings:
 Warning	1301	Result of cast_as_binary() was larger than max_allowed_packet (1048576) - truncated
 Warning	1301	Result of weight_string() was larger than max_allowed_packet (1048576) - truncated
 set global max_allowed_packet=default;
+#
+# Start of 10.1 tests
+#
+#
+# MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field
+#
+CREATE TABLE t1 (a INT(6) ZEROFILL);
+INSERT INTO t1 VALUES (1),(2);
+SELECT * FROM t1 WHERE a=1;
+a
+000001
+SELECT * FROM t1 WHERE WEIGHT_STRING(a) IS NULL;
+a
+000001
+000002
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+a
+000001
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 1) and isnull(weight_string(`test`.`t1`.`a`)))
+ALTER TABLE t1 MODIFY a DOUBLE ZEROFILL;
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+a
+0000000000000000000001
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 1) and isnull(weight_string(`test`.`t1`.`a`)))
+ALTER TABLE t1 MODIFY a DECIMAL(10,1) ZEROFILL;
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+a
+000000001.0
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 1) and isnull(weight_string(`test`.`t1`.`a`)))
+DROP TABLE t1;
+#
+# End of 10.1 tests
+#

mysql-test/r/null.result

@@ -1427,15 +1427,15 @@ a
 EXPLAIN EXTENDED
 SELECT * FROM t1 WHERE a=10 AND NULLIF(a,2011.1)='2011';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where 0
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 2010) and ((case when 2010 = 2011 then NULL else `test`.`t1`.`a` end) = '2011'))
 EXPLAIN EXTENDED
 SELECT * FROM t1 WHERE a=10 AND NULLIF(a,2011.1)=CONCAT('2011',RAND());
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 2010) and (<cache>((case when 2010 = 2011 then NULL else '2010' end)) = concat('2011',rand())))
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 2010) and ((case when 2010 = 2011 then NULL else `test`.`t1`.`a` end) = concat('2011',rand())))
 DROP TABLE t1;
 #
 # MDEV-8754 Wrong result for SELECT..WHERE year_field=2020 AND NULLIF(year_field,2010)='2020'
@@ -1456,13 +1456,13 @@ SELECT * FROM t1 WHERE a=2020 AND NULLIF(a,2010)='2020';
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 2020)
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 2020) and ((case when 2020 = 2010 then NULL else `test`.`t1`.`a` end) = '2020'))
 EXPLAIN EXTENDED
 SELECT * FROM t1 WHERE a=2020 AND NULLIF(a,2010)=CONCAT('2020',RAND());
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 Warnings:
-Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 2020) and (<cache>((case when 2020 = 2010 then NULL else '2020' end)) = concat('2020',rand())))
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 2020) and ((case when 2020 = 2010 then NULL else `test`.`t1`.`a` end) = concat('2020',rand())))
 DROP TABLE t1;
 #
 # End of 10.1 tests

mysql-test/r/type_int.result

@@ -13,5 +13,26 @@ Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 2010)
 DROP TABLE t1;
 #
+# MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field
+#
+CREATE TABLE t1 (a INT ZEROFILL);
+INSERT INTO t1 VALUES (128),(129);
+SELECT * FROM t1 WHERE a=128;
+a
+0000000128
+SELECT * FROM t1 WHERE hex(a)='80';
+a
+0000000128
+SELECT * FROM t1 WHERE a=128 AND hex(a)='80';
+a
+0000000128
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=128 AND hex(a)='80';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 128) and (hex(`test`.`t1`.`a`) = '80'))
+DROP TABLE t1;
+#
 # End of 10.1 tests
 #

mysql-test/t/func_encrypt.test

@@ -103,3 +103,21 @@ insert into t1 values (-15818,'requirement\'s');
 select encrypt(f1,f2) as a from t1,(select encrypt(f1,f2) as b from t1) a;
 --enable_result_log
 drop table t1;
+
+--echo #
+--echo # Start of 10.1 tests
+--echo #
+
+--echo #
+--echo # MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field
+--echo #
+CREATE TABLE t1 (a INT(6) ZEROFILL);
+INSERT INTO t1 VALUES (1),(2);
+# This should not propagate a=1 into DES_ENCRYPT
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=1 AND DES_ENCRYPT('test',a)=_latin1 'abc' COLLATE latin1_bin;
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.1 tests
+--echo #

mysql-test/t/func_str.test

@@ -1750,3 +1750,24 @@ set global max_allowed_packet=default;
 --echo #
 --echo # End of 5.6 tests
 --echo #
+
+--echo #
+--echo # Start of 10.1 tests
+--echo #
+
+--echo #
+--echo # MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field
+--echo #
+CREATE TABLE t1 (a BIGINT(20) ZEROFILL);
+INSERT INTO t1 VALUES (18446744073709551615),(0);
+SELECT * FROM t1 WHERE a=18446744073709551615;
+SELECT * FROM t1 WHERE FORMAT(a,0)='18,446,744,073,709,551,615';
+SELECT * FROM t1 WHERE a=18446744073709551615 AND FORMAT(a,0)='18,446,744,073,709,551,615';
+# This should not propagate the equality into FORMAT()
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=18446744073709551615 AND FORMAT(a,0)='18,446,744,073,709,551,615';
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.1 tests
+--echo #

mysql-test/t/func_weight_string.test

@@ -119,3 +119,31 @@ SELECT HEX(WEIGHT_STRING('ab' AS BINARY(1000000000000000000)));
 disconnect conn1;
 connection default;
 set global max_allowed_packet=default;
+
+--echo #
+--echo # Start of 10.1 tests
+--echo #
+
+--echo #
+--echo # MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field
+--echo #
+CREATE TABLE t1 (a INT(6) ZEROFILL);
+INSERT INTO t1 VALUES (1),(2);
+SELECT * FROM t1 WHERE a=1;
+SELECT * FROM t1 WHERE WEIGHT_STRING(a) IS NULL;
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+ALTER TABLE t1 MODIFY a DOUBLE ZEROFILL;
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+ALTER TABLE t1 MODIFY a DECIMAL(10,1) ZEROFILL;
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=1 AND WEIGHT_STRING(a) IS NULL;
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.1 tests
+--echo #

mysql-test/t/type_int.test

@@ -11,6 +11,18 @@ INSERT INTO t1 VALUES (2010),(2020);
 EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=2010 AND a>=2010;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-8369 Unexpected impossible WHERE for a condition on a ZEROFILL field
+--echo #
+CREATE TABLE t1 (a INT ZEROFILL);
+INSERT INTO t1 VALUES (128),(129);
+SELECT * FROM t1 WHERE a=128;
+SELECT * FROM t1 WHERE hex(a)='80';
+SELECT * FROM t1 WHERE a=128 AND hex(a)='80';
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE a=128 AND hex(a)='80';
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.1 tests
 --echo #

sql/field.cc

@@ -1373,41 +1373,12 @@ void Field_num::prepend_zeros(String *value) const
 }
 
 
-/**
-  Convert a numeric value to a zero-filled string
-
-  @param[in]  thd    current thread
-  @param[in]  item   the item to convert
-
-  This function converts a numeric value to a string. In this conversion
-  the zero-fill flag of the field is taken into account.
-  This is required so the resulting string value can be used instead of
-  the field reference when propagating equalities.
-*/
-
-Item *Field_num::convert_zerofill_number_to_string(THD *thd, Item *item) const
-{
-  char buff[MAX_FIELD_WIDTH],*pos;
-  String tmp(buff,sizeof(buff),Field_num::charset()), *res;
-
-  res= item->val_str(&tmp);
-  if (item->is_null())
-    return new (thd->mem_root) Item_null(thd);
-  else
-  {
-    prepend_zeros(res);
-    pos= (char *) sql_strmake (res->ptr(), res->length());
-    return new (thd->mem_root) Item_string(thd, pos, res->length(), Field_num::charset());
-  }
-}
-
-
 Item *Field_num::get_equal_zerofill_const_item(THD *thd, const Context &ctx,
                                                Item *const_item)
 {
   switch (ctx.subst_constraint()) {
   case IDENTITY_SUBST:
-    return convert_zerofill_number_to_string(thd, const_item);
+    return NULL; // Not safe to propagate if not in comparison. See MDEV-8369.
   case ANY_SUBST:
     break;
   }

sql/field.h

@@ -1207,7 +1207,7 @@ protected:
 
 class Field_num :public Field {
 protected:
-  Item *convert_zerofill_number_to_string(THD *thd, Item *item) const;
+  void prepend_zeros(String *value) const;
   Item *get_equal_zerofill_const_item(THD *thd, const Context &ctx,
                                       Item *const_item);
 public:
@@ -1221,7 +1221,6 @@ public:
   enum Derivation derivation(void) const { return DERIVATION_NUMERIC; }
   uint repertoire(void) const { return MY_REPERTOIRE_NUMERIC; }
   CHARSET_INFO *charset(void) const { return &my_charset_numeric; }
-  void prepend_zeros(String *value) const;
   Item *get_equal_const_item(THD *thd, const Context &ctx, Item *const_item)
   {
     return (flags & ZEROFILL_FLAG) ?