| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Peter T Mount <peter(at)retep(dot)org(dot)uk>, Joe Conway <joseph(dot)conway(at)home(dot)com>, jason(dot)ory(at)ndchealth(dot)com, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Toast, Text, blob bytea Huh? |
| Date: | 2001-08-24 16:07:44 |
| Message-ID: | 200108241607.f7OG7iB04185@candle.pha.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
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| Lists: | pgsql-hackers |
> No, that's just a coincidence. The reason that TOAST limits fields to
> 1Gb is that the high-order two bits of the varlena length word were
> commandeered as TOAST state indicators. There are now only thirty bits
> available to represent the length of a variable-length Datum; hence the
> hard limit on field width is 1Gb.
>
> I'd think that the "practical" limit is quite a bit less than that, at
> least until we devise an API that lets you read and write toasted values
> in sections.
Yes, passing around multi-gigabytes memory chunks in a process is pretty
slow.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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