Ok, I get that. Really what I am *rooting* for is Aggregate (and Sort By) Push-Down to FDW plugins.
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I can already internalize conditional filters for most cases, and doing a count on the filtered results would be considerably faster in my FDW back-end before all the records and Datums have to be constructed for postgres to do the counting. Similarly, I'm very excited about the potential for FDW to advertise a-priori sort states, so things like external merge-sorts can pass-through the request for sorted data for fields in which sorting is a no-op in my backend. Importantly my IDs are sorted by definition since they are essentially array indexes into the column-store, so joining on them with merge-sort should be blazing fast, but currently time is wasted sorting these pre-sorted fields. Just my 2c, and I'll be tracking the 9.6 progress that includes some of these proposals. Gabe -----Original Message----- From: Tom Lane [mailto:t...@sss.pgh.pa.us] Sent: Thursday, February 25, 2016 11:21 PM To: Gabe F. Rudy <r...@goldenhelix.com> Cc: pgsql-hackers@postgresql.org Subject: Re: [HACKERS] FDW handling count(*) through AnalyzeForeignTable or other constant time push-down "Gabe F. Rudy" <r...@goldenhelix.com> writes: > Is there any way to convince Postgres FDW to leverage the analyze row counts > or even the "double* totalRowCount" returned from the AcquireSampleRows > callback from my AnalyzeForeignTable function so that it does not do a > full-table scan for a COUNT(*) etc? No. In PG's view, ANALYZE-based row counts are imprecise by definition. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
