| From: | Tomas Vondra <tomas(at)vondra(dot)me> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com> |
| Subject: | Re: Adding skip scan (including MDAM style range skip scan) to nbtree |
| Date: | 2025-05-09 16:29:54 |
| Message-ID: | 60b84416-be26-4c43-be75-23652cfa7b66@vondra.me |
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| Lists: | pgsql-hackers |
On 5/9/25 18:09, Peter Geoghegan wrote:
> On Fri, May 9, 2025 at 11:55 AM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
>> Note that "sizeof(FmgrInfo)" is 48 bytes. Prior to skip scan,
>> RelationData.rd_supportinfo would have required 48*5=240 bytes. After
>> skip scan, it would have required 48*6=288 bytes. Maybe 256 bytes is
>> some kind of critical threshold, someplace?
>
> Can you try it with the attached patch?
>
> The patch disables skip support entirely, in a way that should
> eliminate whatever the inherent overhead of adding a sixth support
> routine to nbtree was. It does not remove skip scan itself (that
> should still work with queries that are actually eligible to use skip
> scan, albeit slightly less efficiently with some opclasses).
>
Tried, doesn't seem to affect the results at all.
--
Tomas Vondra
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