| From: | Floris Van Nee <florisvannee(at)Optiver(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, "Thomas Munro" <thomas(dot)munro(at)gmail(dot)com>, James Coleman <jtc331(at)gmail(dot)com>, Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, "Bhushan Uparkar" <bhushan(dot)uparkar(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
| Subject: | RE: Index Skip Scan |
| Date: | 2020-01-22 21:08:59 |
| Message-ID: | 105fd98b36dc4c0cb6b3dc41106b5556@opammb0562.comp.optiver.com |
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| Lists: | pgsql-hackers |
> 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?
>
The loose index scan shouldn't return a tuple twice. It should only be able to skip 'further', so that shouldn't be a problem. Out of curiosity, why can't index scans return the same tuple twice? Is there something in the executor that isn't able to handle this?
-Floris
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