On Thu, Sep 14, 2017 at 2:12 AM, Andres Freund <and...@anarazel.de> wrote:
> This patch gives me roughly 8% speedup in a workload that consists out
> of a fast query that returns a lot of columns. If I apply a few
> other performance patches, this patch itself starts to make a bigger
> difference, of around 11%.
I did a read-through of this patch today. I don't see anything really
serious to complain about here. Somebody might question the use of
the no-inline stuff, but it seems sensible to me in this context.
+ /* not as performance critical & "complicated" */
This comment kinda sucks. I don't think it will be clear to somebody
in 3 years what this means. It's clear enough in context but later I
think it won't be. I suggest dumping this altogether and expanding
the comment up above to encompass this:
Hash and equality functions for system types that are used as cache
key fields. In some cases, we just call the regular SQL-callable
functions for the appropriate data type, but that tends to be a little
slow, and the speed of these functions is performance-critical.
Therefore, for data types that frequently occur as catcache keys, we
hard-code the logic here. Avoiding the overhead of
DirectFunctionCallN(...) is a substantial win, and in certain cases
(like int4) we can adopt a faster hash algorithm as well.
+ {
+ return false;
+ }
Excess braces.
+ * The use of argument specific numbers is encouraged, they're faster, and
+ * insulates the caller from changes in the maximum number of keys.
s/, they're faster/. They're faster/
- if (cache->cc_tupdesc == NULL)
+ if (unlikely(cache->cc_tupdesc == NULL))
CatalogCacheInitializeCache(cache);
I don't think it's this patch's job to do it, but it seems like we
ought to just invent some early-initialization step where things like
this can happen, so that we don't have to branch here at all.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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