Re: problem about maximum row size ?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: zhaoxin <zhaox(at)necas(dot)nec(dot)com(dot)cn>
Cc: pgsql-odbc(at)postgresql(dot)org, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Subject: Re: problem about maximum row size ?
Date: 2006-03-21 17:04:57
Message-ID: 17823.1142960697@sss.pgh.pa.us
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zhaoxin <zhaox(at)necas(dot)nec(dot)com(dot)cn> writes:
> I have a question about maximum row size .
> In pgsql FAQ, I can find this description :
> ...
> Maximum size for a row? 1.6TB
> ...

> does it mean 1600 text column in a table and 1G every column ?

> but, when I test this case by psqlodbc, I got some error :

This was posted in a fairly randomly chosen list, but I think it does
expose an error in the FAQ: you can't fit 1600 TOAST pointers into one
row and so the 1.6TB figure is overoptimistic.

Since TOAST pointers are 20 bytes, a reasonable number for the maximum
number of large toasted fields is about 400, which would make the
correct entry for this question 400Gb. This could be improved by using
a non-default block size, so this should be listed as one of the limits
affected by block size.

regards, tom lane

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