Re: [HACKERS] index-only count(*) for indexes supporting bitmap scans - Mailing list pgsql-hackers

From Andrew Gierth
Subject Re: [HACKERS] index-only count(*) for indexes supporting bitmap scans
Date
Msg-id 87ziflvryn.fsf@news-spur.riddles.org.uk
Whole thread Raw
In response to [HACKERS] index-only count(*) for indexes supporting bitmap scans  (Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru>)
Responses Re: [HACKERS] index-only count(*) for indexes supporting bitmap scans  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
>>>>> "Alexander" == Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru> writes:
Alexander> Structurally, the patch consists of two major parts: aAlexander> specialized executor node

Why?

It strikes me that the significant fact here is not that we're doing
count(*), but that we don't need any columns from the bitmap heap scan
result.  Rather than creating a whole new node, can't the existing
bitmap heapscan be taught to skip fetching the actual table page in
cases where it's all-visible, not lossy, and no columns are needed?

(this would also have the advantage of getting parallelism for free)

-- 
Andrew (irc:RhodiumToad)



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