Introduction
Every major ClickHouse® release introduces new features and performance improvements, but occasionally older experimental features are removed to simplify maintenance and improve long-term stability.
One such change in ClickHouse® 26.3 is the removal of the experimental Hypothesis Skip Index (TYPE hypothesis).
If you experimented with this index type in earlier versions, you'll need to update your schema before upgrading to ClickHouse® 26.3. Otherwise, table creation or schema restoration involving this index type will fail.
In this article, we'll explore what Hypothesis Skip Indexes were, why they were removed, how to identify affected tables, and the recommended migration path.
