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

[Dmitry Lazurkin]

On 25.07.2017 00:31, David G. Johnston wrote:

Basically you want to write something like:

SELECT *
FROM ids
JOIN ( :values_clause ) vc (vid) ON (vc.vid = ids.id <http://ids.id>)​

or

WITH vc AS (SELECT vid FROM .... ORDER BY ... LIMIT )
SELECT *
FROM ids
JOIN vc ON (vid = ids.id <http://ids.id>)


This query uses JOIN plan node as IN (VALUES ...).

And I have one question. I don't understand why IN-VALUES doesn't use 
Semi-Join? PostgreSQL has Hash Semi-Join...  For which task the database 
has node of this type?