Re: [GENERAL] Perfomance of IN-clause with many elements and possible solutions

​IN-VALUES is just another word for "TABLE" which is another word for "RELATION".  Writing relational database queries that use explicit relations is generally going to give you the best performance.

Basically you want to write something like:

SELECT *

FROM ids

JOIN ( :values_clause ) vc (vid) ON (vc.vid = ids.id)​

or 

WITH vc AS (SELECT vid FROM .... ORDER BY ... LIMIT )

SELECT *

FROM ids

JOIN vc ON (vid = ids.id)

"IN ('l1','l2','l3')" is nice and all but as demonstrated the mechanics of executing that are different, and slower, than processing relations and tuples.  For a small number of items the difference is generally not meaningful and so the convenience of writing (IN (...)) is worth taking.

David J.