Hello PostgreSQL team,
I have encountered what appears to be a planner regression or bug in PostgreSQL 17.4 regarding the use of btree indexes for prefix searches with LIKE 'prefix%'.
A btree index on a text column is not used for a query of the form WHERE col LIKE 'prefix%', even though the index is healthy, statistics are correct, and the query is highly selective.
The same index is used and performs well for an equivalent range query (WHERE col >= 'prefix' AND col < 'nextprefix').
- This behavior persists even after VACUUM FULL, ANALYZE, and index re-creation.
- The column and index use the default collation (en_US.UTF-8).
- The index is valid and ready.
- The planner does not use the index for LIKE 'prefix%', but does for the equivalent range.
- Rewriting the query as a range (col >= 'prefix' AND col < 'nextprefix') uses the index and is fast, but this should not be necessary.
Thank you for your attention!
