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Re: Savepoints

From: "Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at>
To: "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>, "Mikheev, Vadim" <vmikheev(at)SECTORBASE(dot)COM>
Cc: "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Savepoints
Date: 2002-01-25 21:03:53
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Lists: pgsql-hackers
> Now, with MVCC, the backend has to read through the redo segment to get

You mean rollback segment, but ...

> the original data value for that row.

Will only need to be looked up if the row is currently beeing modified by 
a not yet comitted txn (at least in the default read committed mode)  

> Now, while rollback segments do help with cleaning out old UPDATE rows,
> how does it improve DELETE performance?  Seems it would just mark it as
> expired like we do now.

delete would probably be: 
1. mark original deleted and write whole row to RS

I don't think you would like to mix looking up deleted rows in heap
but updated rows in RS


PS: not that I like overwrite with MVCC now
If you think of VACUUM as garbage collection PG is highly trendy with
the non-overwriting smgr.


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