v.21.2Improvements

Restrict MODIFY TTL Queries for Legacy MergeTree Tables

Official CH changelog text
Restrict MODIFY TTL queries for MergeTree tables created in old syntax. Previously the query succeeded, but actually it had no effect. #19064 (Anton Popov).
Restrict MODIFY TTL queries on MergeTree tables created using the old syntax to prevent ineffective changes.

Why it matters

Previously, users could run MODIFY TTL queries on MergeTree tables defined with the old syntax, but these queries would succeed without actually applying any changes. This feature prevents such misleading executions by restricting MODIFY TTL on old syntax tables, improving the correctness and reliability of TTL modifications.

How to use it

Users do not need to take any explicit action to enable this restriction. When attempting to run MODIFY TTL on MergeTree tables created with the old syntax, the query will now be blocked to avoid ineffective operations.

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