Heads up: counting may be slow in PostgreSQL

The linked article points out that COUNT queries might be unexpectetly slow in psql.

If you just need to know "are there any records" use any?. This uses SELECT 1 AS one FROM ... LIMIT 1 under the hood.
If you just need to know "are there no records" use empty? or none?. This uses SELECT 1 AS one FROM ... LIMIT 1 under the hood.

In short: Replace foo.count > 0 with foo.any? or foo.count == 0 with foo.none?

Michael Leimst├Ądtner about 1 month ago
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