Re: Using POPCNT and other advanced bit manipulation instructions - Mailing list pgsql-hackers

From Gavin Flower
Subject Re: Using POPCNT and other advanced bit manipulation instructions
Date
Msg-id 7cd3ffa8-4889-1188-4baa-80ac4396be54@archidevsys.co.nz
Whole thread Raw
In response to Re: Using POPCNT and other advanced bit manipulation instructions  (Alvaro Herrera <alvherre@2ndquadrant.com>)
Responses Re: Using POPCNT and other advanced bit manipulation instructions  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
On 14/02/2019 11:17, Alvaro Herrera wrote:
> On 2019-Feb-13, Alvaro Herrera wrote:
>
>> It definitely is ... plans have changed from using IndexOnly scans to
>> Seqscans, which is likely fallout from the visibilitymap_count() change.
> I think the problem here is that "unsigned long" is 32 bits in this
> machine:

[...]

 From my memory of reading of K&R many moons ago, it said that C only 
guarantees that the lengths are such that

byte <= half word <= word <= long

But I don't recall ever seeing a long less than 32 bits!


Cheers,
Gavin



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