From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Robert Haas <robertmhaas(at)gmail(dot)com>, Jeevan Ladhe <jeevan(dot)ladhe(at)enterprisedb(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Binary search in fmgr_isbuiltin() is a bottleneck. |
Date: | 2017-10-05 18:54:02 |
Message-ID: | 15362.1507229642@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2017-10-05 17:08:39 +0300, Heikki Linnakangas wrote:
>> BTW, there's some alignment padding in FmgrBuiltin, when MAXIMUM_ALIGNOF==8.
>> You could easily shrink the struct from 32 to 24 bytes by moving funcName to
>> the end of the struct:
> Yea, that's probably worthwhile, although I suspect it's not a huge save
> overall. Do you just want to commit that?
+1
>> If we care about cache efficiency here, we could move funcName out of the
>> fmgr_builtins array, to a separate array of the same size.
> When'd that be beneficial? fmgr_builtins is pretty much only used for
> internal-language CREATE FUNCTIONs? In other cases oid bounds + mapping
> array should filter out the access before fmgr_builtins is accessed.
I'm -1 on this, it would complicate using the data structure to look up
the name of a built-in function from its OID. (Don't know that anyone
actually does that, but I see no reason to break their code if they do.)
regards, tom lane
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