Bug #28652826 THE CONTINUATION OF BUG 27968952 .. CRASH &

CORRUPTION WITH GCOLS

Problem:
Wrong value of BLOB column is being updated into secondary index.

Analysis:
For REPLACE query, If INSERT operation finds same key value in
cluster index, It converts INSERT into UPDATE operation. UPDATE
operation build the update vector.
For virtual generated columns, my_eval_gcolumn_expr() wrties
the "old" BLOB column directly into Field_blob::value.
If this UPDATE operation fails due to dup_key error in secondary
index. We go back to the handler and fetch the key value which
causes the error.
If that key is defined on virtual BLOB column. Since the "old" value
has over-written the "new" value. We get "old" BLOB value.
Therefore we update wrong row and end up with data corruption.

Solution:
If INSERT operation returns DUP_KEY error to the handler.
We recalculate data for generated columns before reading the key
value.

Change-Id: I8fd4526cac6b0c905fc6125e24ed85f524ae1343
Reviewed by : Sergey Glukhov<sergey.glukhov@oracle.com>

Author: sachinagarwal1111

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

@@ -639,3 +639,24 @@ SELECT (SELECT MAX(c) FROM v);
 (SELECT MAX(c) FROM v)
 1
 DROP TABLE v;
+#
+# Bug #28652826	THE CONTINUATION OF BUG 27968952 .. CRASH & CORRUPTION
+# WITH GCOLS
+#
+CREATE TABLE t(
+a INT NOT NULL,
+b INT NOT NULL,
+c INT NOT NULL,
+g MEDIUMTEXT GENERATED ALWAYS AS((a <> b)) VIRTUAL,
+UNIQUE KEY i0000 (a),
+UNIQUE KEY i0001 (g(78))
+) ENGINE=INNODB;
+REPLACE INTO t(a, b, c) VALUES (1,8,9);
+REPLACE INTO t(a, b, c) VALUES (0,0,10);
+REPLACE INTO t(a, b, c) VALUES (4,4,11);
+REPLACE INTO t(a, b, c) VALUES (0,7,12);
+REPLACE INTO t(a, b, c) VALUES (0,0,13);
+SELECT * FROM t;
+a	b	c	g
+0	0	13	0
+DROP TABLE t;

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

@@ -611,3 +611,24 @@ KEY(c,b(1))) charset utf8mb4;
 INSERT INTO v (a,c) VALUES (1,1);
 SELECT (SELECT MAX(c) FROM v);
 DROP TABLE v;
+
+--echo #
+--echo # Bug #28652826	THE CONTINUATION OF BUG 27968952 .. CRASH & CORRUPTION
+--echo # WITH GCOLS
+--echo #
+
+CREATE TABLE t(
+  a INT NOT NULL,
+  b INT NOT NULL,
+  c INT NOT NULL,
+  g MEDIUMTEXT GENERATED ALWAYS AS((a <> b)) VIRTUAL,
+  UNIQUE KEY i0000 (a),
+  UNIQUE KEY i0001 (g(78))
+) ENGINE=INNODB;
+REPLACE INTO t(a, b, c) VALUES (1,8,9);
+REPLACE INTO t(a, b, c) VALUES (0,0,10);
+REPLACE INTO t(a, b, c) VALUES (4,4,11);
+REPLACE INTO t(a, b, c) VALUES (0,7,12);
+REPLACE INTO t(a, b, c) VALUES (0,0,13);
+SELECT * FROM t;
+DROP TABLE t;

sql/sql_insert.cc

@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1623,6 +1623,14 @@ int write_record(THD *thd, TABLE *table, COPY_INFO *info, COPY_INFO *update)
 	    goto err;
 	  }
 	}
+	/*
+          If we convert INSERT operation internally to an UPDATE.
+          An INSERT operation may update table->vfield for BLOB fields,
+          So here we recalculate data for generated columns.
+	*/
+        if (table->vfield) {
+          update_generated_write_fields(table->write_set, table);
+        }
 	key_copy((uchar*) key,table->record[0],table->key_info+key_nr,0);
 	if ((error=(table->file->ha_index_read_idx_map(table->record[1],key_nr,
                                                        (uchar*) key, HA_WHOLE_KEY,
@@ -1808,6 +1816,7 @@ int write_record(THD *thd, TABLE *table, COPY_INFO *info, COPY_INFO *update)
           we just should not expose this fact to users by invoking
           ON UPDATE triggers.
 	*/
+
 	if (last_uniq_key(table,key_nr) &&
 	    !table->file->referenced_by_foreign_key() &&
             (!table->triggers || !table->triggers->has_delete_triggers()))