Re: Storage Model for Partitioning

From: Richard Huxton <dev(at)archonet(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Storage Model for Partitioning
Date: 2008-01-11 11:34:17
Message-ID: 47875439.2050309@archonet.com
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More dumb user questions...

Simon Riggs wrote:
> 1. Partitions are Contiguous Ranges of Blocks
>
> Partitions are a simple subset of a table, i.e. a contiguous range of
> blocks within the main block range of the table.

> b) Fixed partitioning - we define partitions as static ranges of blocks,
> which may leave us with holes in the range of BlockNumbers, plus each
> partition has a maximum size that it cannot expand beyond. Probably
> unacceptable.

Clearly not going to make anyone happy if you can't fit 1.1GB of data
into your partition.

Is the following basically the same as option #3 (multiple RelFileNodes)?

1. Make an on-disk "chunk" much smaller (e.g. 64MB). Each chunk is a
contigous range of blocks.
2. Make a table-partition (implied or explicit constraints) map to
multiple "chunks".
That would reduce fragmentation (you'd have on average 32MB's worth of
blocks wasted per partition) and allow for stretchy partitions at the
cost of an extra layer of indirection.

For the single-partition case you'd not need to split the file of
course, so it would end up looking much like the current arrangement.

--
Richard Huxton
Archonet Ltd

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