Re: reducing the footprint of ScanKeyword (was Re: Large writable variables) - Mailing list pgsql-hackers

From Tom Lane
Subject Re: reducing the footprint of ScanKeyword (was Re: Large writable variables)
Date
Msg-id 1645.1545503315@sss.pgh.pa.us
Whole thread Raw
In response to Re: reducing the footprint of ScanKeyword (was Re: Large writablevariables)  (Andres Freund <andres@anarazel.de>)
List pgsql-hackers
Andres Freund <andres@anarazel.de> writes:
> On 2018-12-22 12:20:00 -0500, Tom Lane wrote:
>> I like that idea a *lot*, actually, because it offers the opportunity
>> to decouple this mechanism from all assumptions about what the
>> auxiliary data for a keyword is.

> OTOH, it doubles or triples the number of cachelines accessed when
> encountering a keyword.

Compared to what?  The current situation in that regard is a mess.

Also, AFAICS this proposal involves the least amount of data touched
during the lookup phase of anything we've discussed, so I do not even
accept that your criticism is correct.  One extra cacheline fetch
to get the aux data for a particular keyword after the search is not
going to tip the scales away from this being a win.

            regards, tom lane


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