Re: Index Skip Scan - Mailing list pgsql-hackers

From Peter Geoghegan
Subject Re: Index Skip Scan
Date
Msg-id CAH2-Wzm0kLCdnM7rh8MC225E6befVYFTdHGv7-LgKXk32mTXsg@mail.gmail.com
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In response to Re: Index Skip Scan  (Peter Geoghegan <pg@bowt.ie>)
Responses RE: Index Skip Scan  (Floris Van Nee <florisvannee@Optiver.com>)
List pgsql-hackers
On Wed, Jan 22, 2020 at 10:55 AM Peter Geoghegan <pg@bowt.ie> wrote:
> This is a good summary. This is the kind of scenario I had in mind
> when I expressed a general concern about "stopping between pages".
> Processing a whole page at a time is a crucial part of how
> _bt_readpage() currently deals with concurrent page splits.

Note in particular that index scans cannot return the same index tuple
twice -- processing a page at a time ensures that that cannot happen.

Can a loose index scan return the same tuple (i.e. a tuple with the
same heap TID) to the executor more than once?

-- 
Peter Geoghegan



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