MDEV-20495 Assertion `precision > 0' failed in decimal_bin_size upon CREATE .. SELECT with zerofilled decimal

Also fixes:

MDEV-20560 Assertion `precision > 0' failed in decimal_bin_size upon SELECT with MOD short unsigned decimal

Changing the way how Item_func_mod calculates its max_length.
It now uses decimal_precision(), decimal_scale() and unsigned_flag
of its arguments, like all other Item_num_op descendants do.

11 files changed, 222 insertions, 7 deletions

diff --git a/mysql-test/r/ctype_binary.result b/mysql-test/r/ctype_binary.result
index 3fc440b8354..fd709176ea9 100644
--- a/mysql-test/r/ctype_binary.result
+++ b/mysql-test/r/ctype_binary.result
@@ -102,7 +102,7 @@ create table t1 as select concat(1 % 2) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varbinary(1) DEFAULT NULL
+  `c1` varbinary(2) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(-1));
diff --git a/mysql-test/r/ctype_cp1251.result b/mysql-test/r/ctype_cp1251.result
index 9d5dea2f286..426a06165a7 100644
--- a/mysql-test/r/ctype_cp1251.result
+++ b/mysql-test/r/ctype_cp1251.result
@@ -494,7 +494,7 @@ create table t1 as select concat(1 % 2) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varchar(1) CHARACTER SET cp1251 DEFAULT NULL
+  `c1` varchar(2) CHARACTER SET cp1251 DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(-1));
diff --git a/mysql-test/r/ctype_latin1.result b/mysql-test/r/ctype_latin1.result
index db9d03a8656..4273f71bac9 100644
--- a/mysql-test/r/ctype_latin1.result
+++ b/mysql-test/r/ctype_latin1.result
@@ -676,7 +676,7 @@ create table t1 as select concat(1 % 2) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varchar(1) DEFAULT NULL
+  `c1` varchar(2) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(-1));
diff --git a/mysql-test/r/ctype_ucs.result b/mysql-test/r/ctype_ucs.result
index 1c9e31d3a06..a49050e6e94 100644
--- a/mysql-test/r/ctype_ucs.result
+++ b/mysql-test/r/ctype_ucs.result
@@ -1492,7 +1492,7 @@ create table t1 as select concat(1 % 2) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varchar(1) CHARACTER SET ucs2 DEFAULT NULL
+  `c1` varchar(2) CHARACTER SET ucs2 DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(-1));
diff --git a/mysql-test/r/ctype_utf8.result b/mysql-test/r/ctype_utf8.result
index fee27ef177f..6829b19f59d 100644
--- a/mysql-test/r/ctype_utf8.result
+++ b/mysql-test/r/ctype_utf8.result
@@ -2313,7 +2313,7 @@ create table t1 as select concat(1 % 2) as c1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `c1` varchar(1) CHARACTER SET utf8 DEFAULT NULL
+  `c1` varchar(2) CHARACTER SET utf8 DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(-1));
diff --git a/mysql-test/r/func_math.result b/mysql-test/r/func_math.result
index 66bbb25b309..6edaa2e4d96 100644
--- a/mysql-test/r/func_math.result
+++ b/mysql-test/r/func_math.result
@@ -771,5 +771,63 @@ STDDEV_SAMP(ROUND('0', 309))
 0
 DROP TABLE t1;
 #
+# MDEV-20495 Assertion `precision > 0' failed in decimal_bin_size upon CREATE .. SELECT with zerofilled decimal
+#
+# Testing that dyadic arithmetic operations are symmetric
+# for (+1) and (-1) and produce the same length in CONCAT(),
+# because (+1) and (-1) have the same data type: signed int.
+CREATE TABLE t1 AS SELECT
+CONCAT(+1%2.0),
+CONCAT(-1%2.0),
+CONCAT(+1/2.0),
+CONCAT(-1/2.0),
+CONCAT(+1*2.0),
+CONCAT(-1*2.0),
+CONCAT(+1+2.0),
+CONCAT(-1+2.0),
+CONCAT(+1-2.0),
+CONCAT(-1-2.0);
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `CONCAT(+1%2.0)` varchar(4) DEFAULT NULL,
+  `CONCAT(-1%2.0)` varchar(4) DEFAULT NULL,
+  `CONCAT(+1/2.0)` varchar(8) DEFAULT NULL,
+  `CONCAT(-1/2.0)` varchar(8) DEFAULT NULL,
+  `CONCAT(+1*2.0)` varchar(5) NOT NULL DEFAULT '',
+  `CONCAT(-1*2.0)` varchar(5) NOT NULL DEFAULT '',
+  `CONCAT(+1+2.0)` varchar(5) NOT NULL DEFAULT '',
+  `CONCAT(-1+2.0)` varchar(5) NOT NULL DEFAULT '',
+  `CONCAT(+1-2.0)` varchar(5) NOT NULL DEFAULT '',
+  `CONCAT(-1-2.0)` varchar(5) NOT NULL DEFAULT ''
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1;
+CREATE TABLE t1 AS SELECT
+CONCAT(+1%2),
+CONCAT(-1%2),
+CONCAT(+1/2),
+CONCAT(-1/2),
+CONCAT(+1*2),
+CONCAT(-1*2),
+CONCAT(+1+2),
+CONCAT(-1+2),
+CONCAT(+1-2),
+CONCAT(-1-2);
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `CONCAT(+1%2)` varchar(2) DEFAULT NULL,
+  `CONCAT(-1%2)` varchar(2) DEFAULT NULL,
+  `CONCAT(+1/2)` varchar(7) DEFAULT NULL,
+  `CONCAT(-1/2)` varchar(7) DEFAULT NULL,
+  `CONCAT(+1*2)` varchar(3) NOT NULL DEFAULT '',
+  `CONCAT(-1*2)` varchar(3) NOT NULL DEFAULT '',
+  `CONCAT(+1+2)` varchar(3) NOT NULL DEFAULT '',
+  `CONCAT(-1+2)` varchar(3) NOT NULL DEFAULT '',
+  `CONCAT(+1-2)` varchar(3) NOT NULL DEFAULT '',
+  `CONCAT(-1-2)` varchar(3) NOT NULL DEFAULT ''
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1;
+#
 # End of 5.5 tests
 #
diff --git a/mysql-test/r/func_time.result b/mysql-test/r/func_time.result
index 9d478b10d8a..90091ac55c5 100644
--- a/mysql-test/r/func_time.result
+++ b/mysql-test/r/func_time.result
@@ -2100,7 +2100,7 @@ CREATE TABLE t2 AS SELECT CONCAT(FROM_UNIXTIME(CONCAT(a,'10')) MOD FROM_UNIXTIME
 SHOW CREATE TABLE t2;
 Table	Create Table
 t2	CREATE TABLE `t2` (
-  `f2` varchar(26) DEFAULT NULL
+  `f2` varchar(28) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 SELECT * FROM t2;
 f2
diff --git a/mysql-test/r/type_newdecimal.result b/mysql-test/r/type_newdecimal.result
index 81d1637947c..96053e5a12c 100644
--- a/mysql-test/r/type_newdecimal.result
+++ b/mysql-test/r/type_newdecimal.result
@@ -2039,3 +2039,70 @@ t1	CREATE TABLE `t1` (
   `1.0 * 2.000` decimal(6,4) NOT NULL DEFAULT '0.0000'
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 DROP TABLE t1;
+#
+# MDEV-20495 Assertion `precision > 0' failed in decimal_bin_size upon CREATE .. SELECT with zerofilled decimal
+#
+CREATE TABLE t1 (d DECIMAL(1,0) ZEROFILL);
+CREATE TABLE t2 AS SELECT 0 MOD d AS f FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `f` decimal(1,0) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1, t2;
+CREATE TABLE t1 (d DECIMAL(1,0) UNSIGNED);
+CREATE TABLE t2 AS SELECT 0 MOD d AS f FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `f` decimal(1,0) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE IF EXISTS t1,t2;
+CREATE TABLE t1 (d DECIMAL(1,0) ZEROFILL);
+CREATE TABLE t2 AS SELECT CAST(0 AS UNSIGNED) MOD d AS f FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `f` decimal(1,0) unsigned DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1, t2;
+CREATE TABLE t1 (d DECIMAL(1,0) UNSIGNED);
+CREATE TABLE t2 AS SELECT CAST(0 AS UNSIGNED) MOD d AS f FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `f` decimal(1,0) unsigned DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1,t2;
+#
+# MDEV-20560 Assertion `precision > 0' failed in decimal_bin_size upon SELECT with MOD short unsigned decimal
+#
+CREATE TABLE t1 (a DECIMAL(1,0) UNSIGNED);
+INSERT INTO t1 VALUES (1.0),(2.0);
+SELECT DISTINCT 1 MOD a FROM t1;
+1 MOD a
+0
+1
+CREATE TABLE t2 AS SELECT DISTINCT 1 MOD a AS f FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `f` decimal(1,0) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1, t2;
+CREATE TABLE t1 (a DECIMAL(1,0) UNSIGNED);
+INSERT INTO t1 VALUES (1.0),(2.0);
+SELECT DISTINCT 1 MOD a FROM t1;
+1 MOD a
+0
+1
+CREATE TABLE t2 AS SELECT DISTINCT CAST(1 AS UNSIGNED) MOD a AS f FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `f` decimal(1,0) unsigned DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1, t2;
+#
+# End of 5.5 tests
+#
diff --git a/mysql-test/t/func_math.test b/mysql-test/t/func_math.test
index d31b33b5df9..1b5fa519c09 100644
--- a/mysql-test/t/func_math.test
+++ b/mysql-test/t/func_math.test
@@ -576,6 +576,44 @@ INSERT INTO t1 VALUES (1),(2);
 SELECT STDDEV_SAMP(ROUND('0', 309)) FROM t1;
 DROP TABLE t1;
 
+
+--echo #
+--echo # MDEV-20495 Assertion `precision > 0' failed in decimal_bin_size upon CREATE .. SELECT with zerofilled decimal
+--echo #
+
+--echo # Testing that dyadic arithmetic operations are symmetric
+--echo # for (+1) and (-1) and produce the same length in CONCAT(),
+--echo # because (+1) and (-1) have the same data type: signed int.
+
+CREATE TABLE t1 AS SELECT
+  CONCAT(+1%2.0),
+  CONCAT(-1%2.0),
+  CONCAT(+1/2.0),
+  CONCAT(-1/2.0),
+  CONCAT(+1*2.0),
+  CONCAT(-1*2.0),
+  CONCAT(+1+2.0),
+  CONCAT(-1+2.0),
+  CONCAT(+1-2.0),
+  CONCAT(-1-2.0);
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1 AS SELECT
+  CONCAT(+1%2),
+  CONCAT(-1%2),
+  CONCAT(+1/2),
+  CONCAT(-1/2),
+  CONCAT(+1*2),
+  CONCAT(-1*2),
+  CONCAT(+1+2),
+  CONCAT(-1+2),
+  CONCAT(+1-2),
+  CONCAT(-1-2);
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+
 --echo #
 --echo # End of 5.5 tests
 --echo #
diff --git a/mysql-test/t/type_newdecimal.test b/mysql-test/t/type_newdecimal.test
index adc8eb77198..52d014c6b5f 100644
--- a/mysql-test/t/type_newdecimal.test
+++ b/mysql-test/t/type_newdecimal.test
@@ -1625,3 +1625,48 @@ SHOW CREATE TABLE t1;
 DROP TABLE t1;
 
 
+--echo #
+--echo # MDEV-20495 Assertion `precision > 0' failed in decimal_bin_size upon CREATE .. SELECT with zerofilled decimal
+--echo #
+
+CREATE TABLE t1 (d DECIMAL(1,0) ZEROFILL);
+CREATE TABLE t2 AS SELECT 0 MOD d AS f FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t1, t2;
+
+CREATE TABLE t1 (d DECIMAL(1,0) UNSIGNED);
+CREATE TABLE t2 AS SELECT 0 MOD d AS f FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE IF EXISTS t1,t2;
+
+CREATE TABLE t1 (d DECIMAL(1,0) ZEROFILL);
+CREATE TABLE t2 AS SELECT CAST(0 AS UNSIGNED) MOD d AS f FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t1, t2;
+
+CREATE TABLE t1 (d DECIMAL(1,0) UNSIGNED);
+CREATE TABLE t2 AS SELECT CAST(0 AS UNSIGNED) MOD d AS f FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t1,t2;
+
+--echo #
+--echo # MDEV-20560 Assertion `precision > 0' failed in decimal_bin_size upon SELECT with MOD short unsigned decimal
+--echo #
+
+CREATE TABLE t1 (a DECIMAL(1,0) UNSIGNED);
+INSERT INTO t1 VALUES (1.0),(2.0);
+SELECT DISTINCT 1 MOD a FROM t1;
+CREATE TABLE t2 AS SELECT DISTINCT 1 MOD a AS f FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t1, t2;
+
+CREATE TABLE t1 (a DECIMAL(1,0) UNSIGNED);
+INSERT INTO t1 VALUES (1.0),(2.0);
+SELECT DISTINCT 1 MOD a FROM t1;
+CREATE TABLE t2 AS SELECT DISTINCT CAST(1 AS UNSIGNED) MOD a AS f FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t1, t2;
+
+--echo #
+--echo # End of 5.5 tests
+--echo #
diff --git a/sql/item_func.cc b/sql/item_func.cc
index dad4b89b3bc..f079e5c83db 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -2056,8 +2056,11 @@ my_decimal *Item_func_mod::decimal_op(my_decimal *decimal_value)
 
 void Item_func_mod::result_precision()
 {
+  unsigned_flag= args[0]->unsigned_flag;
   decimals= max(args[0]->decimal_scale(), args[1]->decimal_scale());
-  max_length= max(args[0]->max_length, args[1]->max_length);
+  uint prec= max(args[0]->decimal_precision(), args[1]->decimal_precision());
+  fix_char_length(my_decimal_precision_to_length_no_truncation(prec, decimals,
+                                                               unsigned_flag));
 }
 
 
@@ -2065,6 +2068,10 @@ void Item_func_mod::fix_length_and_dec()
 {
   Item_num_op::fix_length_and_dec();
   maybe_null= 1;
+  /*
+    result_precision() sets unsigned_flag for INT_RESULT and DECIMAL_RESULT.
+    Here we need to set it in case of REAL_RESULT.
+  */
   unsigned_flag= args[0]->unsigned_flag;
 }