Re: Equivalent praxis to CLUSTERED INDEX? - Mailing list pgsql-performance

From Bruce Momjian
Subject Re: Equivalent praxis to CLUSTERED INDEX?
Date
Msg-id 200408271748.i7RHmfJ15766@candle.pha.pa.us
Whole thread Raw
In response to Re: Equivalent praxis to CLUSTERED INDEX?  (Adi Alurkar <adi@sf.net>)
Responses Re: Equivalent praxis to CLUSTERED INDEX?  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Equivalent praxis to CLUSTERED INDEX?  (Greg Stark <gsstark@mit.edu>)
Re: Equivalent praxis to CLUSTERED INDEX?  (Greg Stark <gsstark@mit.edu>)
Re: Equivalent praxis to CLUSTERED INDEX?  (Mischa Sandberg <ischamay.andbergsay@activestateway.com>)
List pgsql-performance
Adi Alurkar wrote:
> IIRC it it to reduce the "overflow" of data or what oracle calls
> chained rows. i.e if a table has variable length columns and 10 rows
> get inserted into a datapage, if this datapage is full and one of the
> variable length field gets updated the row will now "overflow" into
> another datapage, but if the datapage is created with an appropriate
> amount of free space the updated row will be stored in one single
> datapage.

Agreed.  What I am wondering is with our system where every update gets
a new row, how would this help us?  I know we try to keep an update on
the same row as the original, but is there any significant performance
benefit to doing that which would offset the compaction advantage?

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