Re: Wal -long transaction - Mailing list pgsql-general

From Greg Stark
Subject Re: Wal -long transaction
Date
Msg-id 873bhmkxa7.fsf@stark.xeocode.com
Whole thread Raw
In response to Re: Wal -long transaction  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Wal -long transaction  (Ron Mayer <rm_pg@cheapcomplexdevices.com>)
List pgsql-general
Tom Lane <tgl@sss.pgh.pa.us> writes:

> Of course, there's no free lunch --- the price we pay for escaping
> rollback-segment-overflow is table bloat if you don't vacuum often
> enough.

Well it's worse than that. If you have long-running transactions that would
cause rollback-segment-overflow in Oracle then the equivalent price in
Postgres would be table bloat *regardless* of how frequently you vacuum.

I suppose you can argue it's not "bloat" as long as you reach a steady state.
But the extra space in the tables is a performance cost on every sequential
scan and on every cache miss it causes whatever you call it.

I'm not saying I like rollback segments better, just yes, TANSTAAFL.

--
greg

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