From 1265bfc30d5bd692caecc65e6df3a19491949d0d Mon Sep 17 00:00:00 2001
From: Anway Durge <124391429+itzanway@users.noreply.github.com>
Date: Tue, 10 Mar 2026 22:42:40 +0530
Subject: [PATCH] MDEV-38899 Fix Assertion \!((f->flags & 4096U) &&
 f->vcol_info)\ upon RBR with NOBLOB

Problem:
When using Row-Based Replication (RBR) with binlog_row_image = NOBLOB,
operations on a table with a UNIQUE constraint on a BLOB NOT NULL column
cause a debug assertion failure in prepare_record() on the replica.

A UNIQUE index on a BLOB creates a hidden virtual column (to store the
blob's hash). This hidden virtual column inherits the NOT NULL property
and receives the NO_DEFAULT_VALUE_FLAG (4096U). During replication, if
the blob isn't included in the row image, prepare_record() evaluates
missing columns and hits the overly strict assertion.

Solution:
Virtual columns evaluate their own expressions and do not use the default
value mechanism. It is completely valid for them (especially automatically
generated hidden ones) to have NO_DEFAULT_VALUE_FLAG set.

Removed the invalid assertion:
DBUG_ASSERT(!((f->flags & NO_DEFAULT_VALUE_FLAG) && f->vcol_info));
Added an MTR test case to prevent future regressions.
---
 .../suite/rpl/r/rpl_noblob_unique_blob.result | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 mysql-test/suite/rpl/r/rpl_noblob_unique_blob.result

diff --git a/mysql-test/suite/rpl/r/rpl_noblob_unique_blob.result b/mysql-test/suite/rpl/r/rpl_noblob_unique_blob.result
new file mode 100644
index 0000000000000..ae8c879ddf061
--- /dev/null
+++ b/mysql-test/suite/rpl/r/rpl_noblob_unique_blob.result
@@ -0,0 +1,20 @@
+include/master-slave.inc
+[connection master]
+#
+# MDEV-38899 Assertion !((f->flags & 4096U) && f->vcol_info)
+# upon RBR with NOBLOB and unique blob
+#
+SET binlog_row_image = NOBLOB;
+CREATE TABLE t (pk INT PRIMARY KEY, a BLOB NOT NULL, UNIQUE(a));
+INSERT IGNORE INTO t (pk) VALUES (1),(2);
+Warnings:
+Warning	1364	Field 'a' doesn't have a default value
+Warning	1062	Duplicate entry '' for key 'a'
+include/sync_slave_sql_with_master.inc
+# Verify data on slave
+SELECT pk FROM t ORDER BY pk;
+pk
+1
+[connection master]
+DROP TABLE t;
+include/rpl_end.inc
\ No newline at end of file