| From: | Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com> |
|---|---|
| To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: ALTER TABLE ADD COLUMN fast default |
| Date: | 2018-03-14 02:10:40 |
| Message-ID: | 78B32C8F-7D8A-4B55-A610-210E06907FFC@2ndquadrant.com |
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| Lists: | pgsql-hackers |
> On Mar 14, 2018, at 10:58 AM, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
>
> On 14 March 2018 at 11:36, Andrew Dunstan
> <andrew(dot)dunstan(at)2ndquadrant(dot)com> wrote:
>> Here are the benchmark results from the v15 patch. Fairly similar to
>> previous results. I'm going to run some profiling again to see if I
>> can identify any glaring hotspots. I do suspect that the "physical
>> tlist" optimization sometimes turns out not to be one. It seems
>> perverse to be able to improve a query's performance by dropping a
>> column.
>
> Can you explain what "fdnmiss" is that appears in the results?
>
>
It’s the patched code run against a materialized version of the table, i.e. one with no missing attributes.
Cheers
Andrew
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