Fixed bug #32335.

Comparison of a BIGINT NOT NULL column with a constant arithmetic
expression that evaluates to NULL caused error 1048: "Column '...'
cannot be null".

Made convert_constant_item() check if the constant expression is NULL
before attempting to store it in a field. Attempts to store NULL in a
NOT NULL field caused query errors.

mysql-test/r/select.result

@@ -4322,4 +4322,10 @@ c3
 DROP TABLE t1;
 DROP TABLE t2;
 
+CREATE TABLE t1 (c1 BIGINT NOT NULL);
+INSERT INTO t1 (c1) VALUES (1);
+SELECT * FROM t1 WHERE c1 > NULL + 1;
+c1
+DROP TABLE t1;
+
 End of 5.0 tests

mysql-test/t/select.test

@@ -3661,4 +3661,15 @@ DROP TABLE t2;
 
 ###########################################################################
 
+#
+# Bug #32335: Error on BIGINT > NULL + 1 
+#
+
+CREATE TABLE t1 (c1 BIGINT NOT NULL);
+INSERT INTO t1 (c1) VALUES (1);
+SELECT * FROM t1 WHERE c1 > NULL + 1;
+DROP TABLE t1;
+
+--echo
+
 --echo End of 5.0 tests

sql/item_cmpfunc.cc

@@ -350,11 +350,12 @@ static bool convert_constant_item(THD *thd, Field *field, Item **item)
     thd->variables.sql_mode= (orig_sql_mode & ~MODE_NO_ZERO_DATE) | 
                              MODE_INVALID_DATES;
     thd->count_cuted_fields= CHECK_FIELD_IGNORE;
-    if (!(*item)->save_in_field(field, 1) && !((*item)->null_value))
+    if (!(*item)->is_null() && !(*item)->save_in_field(field, 1))
     {
       Item *tmp=new Item_int_with_ref(field->val_int(), *item,
                                       test(field->flags & UNSIGNED_FLAG));
       thd->variables.sql_mode= orig_sql_mode;
+      thd->count_cuted_fields= orig_count_cuted_fields;
       if (tmp)
         thd->change_item_tree(item, tmp);
       return 1;					// Item was replaced