Re: [HACKERS] sort on huge table - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [HACKERS] sort on huge table
Date
Msg-id 20868.939827421@sss.pgh.pa.us
Whole thread Raw
In response to Re: [HACKERS] sort on huge table  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: [HACKERS] sort on huge table  (Tatsuo Ishii <t-ishii@sra.co.jp>)
List pgsql-hackers
I wrote:
> The current sorting code will fail if the data volume exceeds whatever
> the maximum file size is on your OS.  (Actually, if long is 32 bits,
> it might fail at 2gig even if your OS can handle 4gig; not sure, but
> it is doing signed-long arithmetic with byte offsets...)

> I am just about to commit code that fixes this by allowing temp files
> to have multiple segments like tables can.

OK, committed.  I have tested this code using a small RELSEG_SIZE,
and it seems to work, but I don't have the spare disk space to try
a full-scale test with > 4Gb of data.  Anyone care to try it?

I have not yet done anything about the excessive space consumption
(4x data volume), so plan on using 16+Gb of diskspace to sort a 4+Gb
table --- and that's not counting where you put the output ;-)
        regards, tom lane


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