FB8-92: Checking for NULL while preparing write set according to binl…

…og_row_image (facebook#990) (facebook#990)

Summary:
Jira issue: https://jira.percona.com/browse/FB8-92

Reference Patch: facebook@f3dc487

Field::cmp_binary_offset returns 0 when comparing a NULL text
field and an empty string leading to the field not being logged when the
value is changed from NULL to empty string. This fix first checks if
both AI and BI fields are not NULL before comparing them.

Originally Reviewed By: santoshbanda

Pull Request resolved: facebook#990

Differential Revision: D14652424 (facebook@b6a8e1d)

fbshipit-source-id: 61a8844cc3a

mysql-test/suite/rpl/t/rpl_row_img_sanity.test

@@ -394,6 +394,7 @@ while (`SELECT HEX(@img_types) != HEX('')`)
     -- connection master
     CREATE TABLE t (c1 int, c2 int, c3 blob, primary key(c1));
     INSERT INTO t VALUES (1,2,"a");
+    INSERT INTO t VALUES (2,4,NULL);
 
 
     --source include/sync_slave_sql_with_master.inc
@@ -412,7 +413,7 @@ while (`SELECT HEX(@img_types) != HEX('')`)
     -- let $row_img_expected_slave = $row_img_expected_master
     -- source include/rpl_row_img_parts_master_slave.inc
 
-    -- let $row_img_query= INSERT INTO t VALUES (1, 4, "a") ON DUPLICATE KEY UPDATE c2 = c2 + 2, c3 = c3;
+    -- let $row_img_query= INSERT INTO t VALUES (1, 4, "a") AS alias ON DUPLICATE KEY UPDATE c2 = alias.c2 + 2, c3 = alias.c3;
     if (`SELECT @@binlog_row_image = "MINIMAL"`)
     {
       -- let $row_img_expected_master= 1:1 | 2:6
@@ -424,6 +425,18 @@ while (`SELECT HEX(@img_types) != HEX('')`)
     -- let $row_img_expected_slave = $row_img_expected_master
     -- source include/rpl_row_img_parts_master_slave.inc
 
+    -- let $row_img_query= INSERT INTO t VALUES (2, 4, "") AS alias ON DUPLICATE KEY UPDATE c2 = alias.c2, c3 = alias.c3;
+    if (`SELECT @@binlog_row_image = "MINIMAL"`)
+    {
+      -- let $row_img_expected_master= 1:2 | 3:''
+    }
+    if (`SELECT @@binlog_row_image = "COMPLETE"`)
+    {
+      -- let $row_img_expected_master= 1:2 2:4 3:NULL | 3:''
+    }
+    -- let $row_img_expected_slave = $row_img_expected_master
+    -- source include/rpl_row_img_parts_master_slave.inc
+
     -- connection master
     DROP TABLE t;
     --source include/sync_slave_sql_with_master.inc

sql/binlog.cc

@@ -11658,6 +11658,7 @@ void binlog_prepare_row_images(const THD *thd, TABLE *table, bool is_update) {
 
         /* compare content, only if fields are not set to NULL */
         else if (!field->is_null() &&
+                 !field->is_null_in_record(table->record[1]) &&
                  !field->cmp_binary_offset(table->s->rec_buff_length))
           bitmap_clear_bit(&table->tmp_write_set, field->field_index());
       }