EC
1623
MySQLWARNINGNotableReplicationHIGH confidence

Statement using system function is unsafe for statement-based replication

Production Risk

Medium — non-deterministic results can cause replica divergence.

What this means

A statement uses a system function (such as RAND(), UUID(), or USER()) that is non-deterministic and may yield different results on the replica.

Why it happens
  1. 1Functions like RAND(), UUID(), FOUND_ROWS(), or ROW_COUNT() produce different values per call.
  2. 2The result depends on session state or timing not replicated to the replica.
How to reproduce
trigger — this will error
trigger — this will error
INSERT INTO t VALUES (UUID());

expected output

Warning 1623: Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT.

Fix 1

Switch to ROW-based replication

Switch to ROW-based replication
SET SESSION binlog_format = 'ROW';

Why this works

ROW format logs the actual inserted value, not the function call.

Fix 2

Pre-compute the value in application code

Pre-compute the value in application code
-- generate UUID in application and pass as literal
INSERT INTO t VALUES ('550e8400-e29b-41d4-a716-446655440000');

Why this works

Using a literal value is safe for statement-based replication.

What not to do

✕

Sources
Official documentation ↗

MySQL 8.0 — 1623 ER_BINLOG_UNSAFE_SYSTEM_FUNCTION

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