Bug #26838771: GCOL: INCORRECT BEHAVIOR WITH UPDATE ON FLY

Issue:
------
When an UPDATE statement is using update on the fly
optimization, generated column related checks are skipped.

Solution:
---------

On 5.7:
Call validate_gc_assignment at an earlier place in
Query_result_update::initialize_tables.

On 8.0 and trunk:
Move the call to validate_gc_assignment
Sql_cmd_update::prepare_inner(). This way no separate
handling is required for single and multi-table UPDATE.

Author: Sreeharsha Ramanavarapu

mysql-test/suite/gcol/r/gcol_update.result

@@ -31,3 +31,22 @@ set global innodb_purge_run_now=1;
 set global innodb_fast_shutdown=0;
 # restart
 drop table t1;
+#
+# Bug #26838771: GCOL: INCORRECT BEHAVIOR WITH UPDATE ON FLY
+#
+CREATE TABLE t1(c1 INT);
+CREATE TABLE t2(c1 INT, c2 JSON, c3 varchar(15) GENERATED ALWAYS AS
+(concat(c2,_utf8mb4'x')) VIRTUAL);
+CREATE TABLE t3(c1 JSON, c2 INT GENERATED ALWAYS AS ((c1 + 1)) VIRTUAL);
+INSERT INTO t2(c1,c2) VALUES(1, '{"tr": "x"}'), (2, '{"tr": "x"}');
+INSERT INTO t3(c1) VALUES(CAST(7 AS JSON));
+UPDATE t3 SET c2 = 0;
+ERROR HY000: The value specified for generated column 'c2' in table 't3' is not allowed.
+UPDATE t3 JOIN t2 ON (t3.c1 = t2.c1) SET t3.c2 = 0;
+ERROR HY000: The value specified for generated column 'c2' in table 't3' is not allowed.
+UPDATE t1 RIGHT JOIN
+t2 ON (t1.c1 = t2.c1),
+t3
+SET t2.c2 = 'tr', t3.c2 = 0;
+ERROR HY000: The value specified for generated column 'c2' in table 't3' is not allowed.
+DROP TABLE t1,t2,t3;

mysql-test/suite/gcol/t/gcol_update.test

@@ -54,3 +54,30 @@ set global innodb_purge_run_now=1;
 set global innodb_fast_shutdown=0;
 --source include/restart_mysqld.inc
 drop table t1;
+
+--echo #
+--echo # Bug #26838771: GCOL: INCORRECT BEHAVIOR WITH UPDATE ON FLY
+--echo #
+
+CREATE TABLE t1(c1 INT);
+CREATE TABLE t2(c1 INT, c2 JSON, c3 varchar(15) GENERATED ALWAYS AS
+                (concat(c2,_utf8mb4'x')) VIRTUAL);
+CREATE TABLE t3(c1 JSON, c2 INT GENERATED ALWAYS AS ((c1 + 1)) VIRTUAL);
+
+INSERT INTO t2(c1,c2) VALUES(1, '{"tr": "x"}'), (2, '{"tr": "x"}');
+INSERT INTO t3(c1) VALUES(CAST(7 AS JSON));
+
+
+--error ER_NON_DEFAULT_VALUE_FOR_GENERATED_COLUMN
+UPDATE t3 SET c2 = 0;
+
+--error ER_NON_DEFAULT_VALUE_FOR_GENERATED_COLUMN
+UPDATE t3 JOIN t2 ON (t3.c1 = t2.c1) SET t3.c2 = 0;
+
+--error ER_NON_DEFAULT_VALUE_FOR_GENERATED_COLUMN
+UPDATE t1 RIGHT JOIN
+       t2 ON (t1.c1 = t2.c1),
+       t3
+SET t2.c2 = 'tr', t3.c2 = 0;
+
+DROP TABLE t1,t2,t3;

sql/sql_update.cc

@@ -2021,6 +2021,9 @@ bool Query_result_update::initialize_tables(JOIN *join)
     List<Item> temp_fields;
     ORDER     group;
     Temp_table_param *tmp_param;
+    if (table->vfield &&
+        validate_gc_assignment(thd, fields, values, table))
+      DBUG_RETURN(0);
 
     if (thd->lex->is_ignore())
       table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
@@ -2080,15 +2083,11 @@ bool Query_result_update::initialize_tables(JOIN *join)
       if (safe_update_on_fly(thd, join->best_ref[0], table_ref, all_tables))
       {
         table->mark_columns_needed_for_update(true/*mark_binlog_columns=true*/);
-	table_to_update= table;			// Update table on the fly
+        table_to_update= table;			// Update table on the fly
 	continue;
       }
     }
     table->mark_columns_needed_for_update(true/*mark_binlog_columns=true*/);
-
-    if (table->vfield &&
-        validate_gc_assignment(thd, fields, values, table))
-      DBUG_RETURN(0);
     /*
       enable uncacheable flag if we update a view with check option
       and check option has a subselect, otherwise, the check option