MDEV-11015 Assertion failed: precision > 0 in decimal_bin_size upon SELECT with DISTINCT, CAST and other functions

Item_func_min_max::fix_length_and_dec() erroneously set max_length
to UINT32_MAX.

Merge notes:
In 10.3 this problem had been fixed earlier.
During merge to 10.3, do a "null merge" in item_func.cc

3 files changed, 60 insertions, 6 deletions

diff --git a/mysql-test/r/func_hybrid_type.result b/mysql-test/r/func_hybrid_type.result
index eeaa79e7dce..dfec8b3210b 100644
--- a/mysql-test/r/func_hybrid_type.result
+++ b/mysql-test/r/func_hybrid_type.result
@@ -2179,10 +2179,10 @@ def					if_______a_b	12	19	19	Y	128	0	63
 def					if_______b_a	12	19	19	Y	128	0	63
 def					ifnull___a_b	12	19	19	Y	128	0	63
 def					ifnull___b_a	12	19	19	Y	128	0	63
-def					least____a_b	12	10	19	Y	128	0	63
-def					least____b_a	12	10	19	Y	128	0	63
-def					greatest_a_b	12	10	19	Y	128	0	63
-def					greatest_b_a	12	10	19	Y	128	0	63
+def					least____a_b	12	19	19	Y	128	0	63
+def					least____b_a	12	19	19	Y	128	0	63
+def					greatest_a_b	12	19	19	Y	128	0	63
+def					greatest_b_a	12	19	19	Y	128	0	63
 case_____a_b	2010-01-01 00:00:00
 case_____b_a	2001-01-01 10:20:30
 coalesce_a_b	2010-01-01 00:00:00
@@ -3034,7 +3034,7 @@ DROP TABLE t1;
 SET timestamp=UNIX_TIMESTAMP('2010-01-01 01:02:03');
 SELECT GREATEST(CURRENT_TIME, CURRENT_DATE), COALESCE(CURRENT_TIME, CURRENT_DATE);
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					GREATEST(CURRENT_TIME, CURRENT_DATE)	12	10	19	N	129	0	63
+def					GREATEST(CURRENT_TIME, CURRENT_DATE)	12	19	19	N	129	0	63
 def					COALESCE(CURRENT_TIME, CURRENT_DATE)	12	19	19	N	129	0	63
 GREATEST(CURRENT_TIME, CURRENT_DATE)	COALESCE(CURRENT_TIME, CURRENT_DATE)
 2010-01-01 01:02:03	2010-01-01 01:02:03
@@ -3427,5 +3427,35 @@ t1	CREATE TABLE `t1` (
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 DROP TABLE t1;
 #
+# MDEV-11015 Assertion failed: precision > 0 in decimal_bin_size upon SELECT with DISTINCT, CAST and other functions
+#
+CREATE TABLE t1 (b LONGBLOB);
+INSERT IGNORE INTO t1 VALUES ('foo'),('bar');
+SELECT DISTINCT - GREATEST( b, CAST( NULL AS DATETIME ) ) AS f FROM t1;
+f
+NULL
+Warnings:
+Warning	1292	Incorrect datetime value: 'foo'
+Warning	1292	Incorrect datetime value: 'bar'
+DROP TABLE t1;
+CREATE TABLE t1 (b LONGBLOB);
+INSERT IGNORE INTO t1 VALUES ('foo'),('bar');
+SELECT DISTINCT - GREATEST( b, CAST( NULL AS TIME) ) AS f FROM t1;
+f
+NULL
+Warnings:
+Warning	1292	Truncated incorrect time value: 'foo'
+Warning	1292	Truncated incorrect time value: 'bar'
+DROP TABLE t1;
+CREATE TABLE t1 (b LONGBLOB);
+INSERT IGNORE INTO t1 VALUES ('foo'),('bar');
+SELECT DISTINCT - GREATEST( b, CAST( NULL AS DATE) ) AS f FROM t1;
+f
+NULL
+Warnings:
+Warning	1292	Incorrect datetime value: 'foo'
+Warning	1292	Incorrect datetime value: 'bar'
+DROP TABLE t1;
+#
 # End of 10.1 tests
 #
diff --git a/mysql-test/t/func_hybrid_type.test b/mysql-test/t/func_hybrid_type.test
index dd8a399025b..c07303f7450 100644
--- a/mysql-test/t/func_hybrid_type.test
+++ b/mysql-test/t/func_hybrid_type.test
@@ -456,6 +456,26 @@ EXECUTE stmt USING @a,@a;
 SHOW CREATE TABLE t1;
 DROP TABLE t1;
 
+
+--echo #
+--echo # MDEV-11015 Assertion failed: precision > 0 in decimal_bin_size upon SELECT with DISTINCT, CAST and other functions
+--echo #
+
+CREATE TABLE t1 (b LONGBLOB);
+INSERT IGNORE INTO t1 VALUES ('foo'),('bar');
+SELECT DISTINCT - GREATEST( b, CAST( NULL AS DATETIME ) ) AS f FROM t1;
+DROP TABLE t1;
+
+CREATE TABLE t1 (b LONGBLOB);
+INSERT IGNORE INTO t1 VALUES ('foo'),('bar');
+SELECT DISTINCT - GREATEST( b, CAST( NULL AS TIME) ) AS f FROM t1;
+DROP TABLE t1;
+
+CREATE TABLE t1 (b LONGBLOB);
+INSERT IGNORE INTO t1 VALUES ('foo'),('bar');
+SELECT DISTINCT - GREATEST( b, CAST( NULL AS DATE) ) AS f FROM t1;
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.1 tests
 --echo #
diff --git a/sql/item_func.cc b/sql/item_func.cc
index a1a2c3f1d1c..86111374175 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -2793,6 +2793,7 @@ void Item_func_min_max::fix_length_and_dec()
 
   switch (tmp_cmp_type) {
   case TIME_RESULT:
+  {
     // At least one temporal argument was found.
     if (temporal_type_count < arg_count)
       maybe_null= true; // Non-temporal-to-temporal conversion can return NULL
@@ -2802,8 +2803,11 @@ void Item_func_min_max::fix_length_and_dec()
       set_if_smaller(decimals, TIME_SECOND_PART_DIGITS);
     else
       decimals= 0;
+    uint len= decimals ? (decimals + 1) : 0;
+    len+= mysql_temporal_int_part_length(temporal_field_type);
+    fix_char_length(len);
     break;
-
+  }
   case STRING_RESULT:
     /*
       All arguments are of string-alike types: