| From: | Noah Misch <noah(at)leadboat(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: ALTER TABLE lock strength reduction patch is unsafe |
| Date: | 2011-12-20 16:23:02 |
| Message-ID: | 20111220162302.GA5979@tornado.leadboat.com |
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| Lists: | pgsql-hackers |
On Mon, Dec 19, 2011 at 11:13:57PM -0500, Tom Lane wrote:
> Noah Misch <noah(at)leadboat(dot)com> writes:
> > I created a function that does this in a loop:
>
> > HeapTuple t;
>
> > CatalogCacheFlushCatalog(ProcedureRelationId);
> > t = SearchSysCache1(PROCOID, ObjectIdGetDatum(42) /* int4in */);
> > if (!HeapTupleIsValid(t))
> > elog(ERROR, "cache lookup failed for function 42");
> > ReleaseSysCache(t);
>
> ... but this performance test seems to me to be entirely misguided,
> because it's testing a situation that isn't going to occur much in the
> field, precisely because the syscache should prevent constant reloads of
> the same syscache entry.
> [ideas for more-realistic tests]
Granted, but I don't hope to reliably measure a change in a macro-benchmark
after seeing a rickety 2% change in a micro-benchmark.
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