Re: GSoC 2017: Foreign Key Arrays

From: Mark Rofail <markm(dot)rofail(at)gmail(dot)com>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, David Steele <david(at)pgmasters(dot)net>, Stephen Frost <sfrost(at)snowman(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: GSoC 2017: Foreign Key Arrays
Date: 2017-07-06 02:02:42
Message-ID: CAJvoCuvgPTPfjCQ383PkMnQ6oFgxY-Z4fXOqzjhmfW9gcoy-fw@mail.gmail.com
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To make the queries fired by the RI triggers GIN indexed. We need to ‒ as
Tom Lane has previously suggested[1] ‒ to replace the query

SELECT 1 FROM ONLY fktable x WHERE $1 = ANY (fkcol) FOR SHARE OF x;

with

SELECT 1 FROM ONLY fktable x WHERE ARRAY[$1] <@ fkcol FOR SHARE OF x;

but since we have @<(anyarray, anyelement) it can be improved to

SELECT 1 FROM ONLY fktable x WHERE $1 @> fkcol FOR SHARE OF x;

and the piece of code responsible for all of this is ri_GenerateQual in
ri_triggers.c.

How to accomplish that is the next step. I don't know if we should hardcode
the "@>" symbol or if we just index the fk table then ri_GenerateQual would
be able to find the operator on it's own.

*What I plan to do:*

- study how to index the fk table upon its creation. I suspect this can
be done in tablecmds.c

*Questions:*

- how can you programmatically in C index a table?

[1] https://www.postgresql.org/message-id/28389.1351094795%40sss.pgh.pa.us

Best Regards,
Mark Rofail

Attachment Content-Type Size
GIN-fk-RI-code-v1.patch text/x-patch 1.3 KB

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