Is the hash index in PostgreSQL thread-safe?

Hash indexes in PostgreSQL are not considered fully thread-safe in the traditional sense. They previously had limitations and did not support WAL (Write-Ahead Logging), which affected reliability and parallelism.

However, starting from PostgreSQL 10 and above, hash indexes have been significantly improved and now support WAL, increasing their reliability and safety during concurrent access.

Nevertheless, in most cases, it is recommended to use B-tree indexes, as they are more versatile and stable for parallel operations.

If high concurrency and thread safety are required, it is better to prefer B-tree indexes.