Horton

Re: TOAST & vacuum

Bruce Momjian <pgman@candle.pha.pa.us>

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From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Jan Wieck <JanWieck@Yahoo.com>
Cc: PostgreSQL HACKERS <pgsql-hackers@postgresql.org>
Date: 2000-07-27T02:10:05Z
Lists: pgsql-hackers 
> FYI,
> 
>     TOAST  is now vacuum-safe. When needed, the toaster creates a
>     second  heap  tuple,  containing  only  plain  or  compressed
>     values.  This one is then returned by the heap access methods
>     to  the  caller,  so  indices  will  never  contain  external
>     references.
> 
>     The  changes  are  covered  by  #ifdef  TOAST_INDICES, so can
>     easily be disabled at the time we have  file  versioning  and
>     can recreate indices during vacuum.

Seems this has some performance advantages.  Un-toasting to traverse a
btree index would be pretty slow.  This way, it is all in the index.

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