Bug #39353: Multiple conditions on timestamp column crashes server

      
The fix for bug 31887 was incomplete : it assumes that all the 
field types returned by the IS_NUM macro are descendants of 
Item_num and tries to zero-fill the values before doing constant
substitution with such fields when they are compared to constant string
values.
The only exception to this is Field_timestamp : it's in the IS_NUM
macro, but is not a descendant of Field_num.
Fixed by excluding timestamp fields (Field_timestamp) when zero-filling
when converting the constant to compare with to a string.
Note that this will not exclude the timestamp columns from const 
propagation.

mysql-test/r/compare.result:
  Bug #39353: test case
mysql-test/t/compare.test:
  Bug #39353: test case
sql/item.cc:
  Bug #39353: don't zero-fill timestamp fields when const propagating
  to a string : they'll be converted to a string in a date/time format
  and not as an integer.

mysql-test/r/compare.result

@@ -90,4 +90,9 @@ Note	1276	Field or reference 'test.t2.a' of SELECT #2 was resolved in SELECT #1
 Note	1276	Field or reference 'test.t2.a' of SELECT #2 was resolved in SELECT #1
 Note	1003	select `test`.`t2`.`a` AS `a`,(select count(0) AS `COUNT(*)` from `test`.`t1` where ((`test`.`t1`.`b` = `test`.`t2`.`a`) and (concat(`test`.`t1`.`b`,`test`.`t1`.`c`) = concat(_latin1'0',`test`.`t2`.`a`,_latin1'01')))) AS `x` from `test`.`t2` order by `test`.`t2`.`a`
 DROP TABLE t1,t2;
+CREATE TABLE t1 (a TIMESTAMP);
+INSERT INTO t1 VALUES (NOW()),(NOW()),(NOW());
+SELECT * FROM t1 WHERE a > '2008-01-01' AND a = '0000-00-00';
+a
+DROP TABLE t1;
 End of 5.0 tests

mysql-test/t/compare.test

@@ -76,4 +76,13 @@ FROM t2 ORDER BY a;
 
 DROP TABLE t1,t2;
 
+#
+# Bug #39353: Multiple conditions on timestamp column crashes server
+#
+
+CREATE TABLE t1 (a TIMESTAMP); 
+INSERT INTO t1 VALUES (NOW()),(NOW()),(NOW());
+SELECT * FROM t1 WHERE a > '2008-01-01' AND a = '0000-00-00';
+DROP TABLE t1;
+
 --echo End of 5.0 tests

sql/item.cc

@@ -4220,7 +4220,12 @@ Item *Item_field::equal_fields_propagator(byte *arg)
     item= this;
   else if (field && (field->flags & ZEROFILL_FLAG) && IS_NUM(field->type()))
   {
-    if (item && cmp_context != INT_RESULT)
+    /*
+      We don't need to zero-fill timestamp columns here because they will be 
+      first converted to a string (in date/time format) and compared as such if
+      compared with another string.
+    */
+    if (item && field->type() != FIELD_TYPE_TIMESTAMP && cmp_context != INT_RESULT)
       convert_zerofill_number_to_string(&item, (Field_num *)field);
     else
       item= this;