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Re: Dynamic Partitioning using Segment Visibility Maps

From: Markus Schiltknecht <markus(at)bluegap(dot)ch>
To: Csaba Nagy <nagy(at)ecircle-ag(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Dynamic Partitioning using Segment Visibility Maps
Date: 2008-01-07 13:20:02
Message-ID: 47822702.5040005@bluegap.ch (view raw or flat)
Thread:
Lists: pgsql-hackers
Hi,

Csaba Nagy wrote:
> Sure, but it could be configurable and should only be enabled if the
> table is marked as partitioned on some condition... 

As I'm regarding SE as an optimization, I disagree here.. As all 
optimizations, SE should conceptually be reasonably close to cost-less 
when unneeded.

> I think it would be
> a bad idea anyway if the DB would start partitioning on some arbitrary
> criteria based on analyzing he table, so the DBA should be the one to
> decide on what criteria to partition.

I absolutely agree for real partitioning, which targets manageability of 
table partitions.

> In particular it could be a bad
> idea on occasions to partition on the clustering criteria for tables
> which were clustered once.

Why is that? AFAIUI, Segment Exclusion combines perfectly well with 
clustering. Or even better, with an upcoming feature to maintain 
clustered ordering. Where do you see disadvantages such an optimization 
for sequential scans?

Regards

Markus


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