From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Ron Johnson <ron(dot)l(dot)johnson(at)cox(dot)net> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: [GENERAL] Large databases, performance |
Date: | 2002-10-08 14:38:02 |
Message-ID: | 1928.1034087882@sss.pgh.pa.us |
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Lists: | pgsql-general pgsql-hackers pgsql-performance pgsql-sql |
Ron Johnson <ron(dot)l(dot)johnson(at)cox(dot)net> writes:
> Not only that, but you get INSERT, UPDATE, DELETE and SELECT performance
> gains with fixed length records, since you don't get fragmentation.
That argument loses a lot of its force when you consider that Postgres
uses non-overwriting storage management. We never do an UPDATE in-place
anyway, and so it matters little whether the updated record is the same
size as the original.
>> Well, maybe. But since 7.1 or so char() and varchar() simply became text
>> with some length restrictions. This was one of the reasons. It also
>> simplified a lot of code.
> How much simpler can you get than fixed-length records?
It's not simpler: it's more complicated, because you need an additional
input item to figure out the size of any given column in a record.
Making sure that that info is available every place it's needed is one
of the costs of supporting a feature like this.
regards, tom lane
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