On 14.11.2013 22:10, Simon Riggs wrote:
On 16 January 2013 00:40, Simon Riggs <si...@2ndquadrant.com> wrote:

SeqAm allows you to specify a plugin that alters the behaviour for
sequence allocation and resetting, aimed specifically at clustering

New command options on end of statement allow syntax
       USING globalseq

Production version of this, ready for commit to PG 9.4

Includes test extension which allows sequences without gaps - "gapless".

Test using seq_test.psql after creating extension.

No dependencies on other patches.

It's pretty hard to review the this without seeing the "other" implementation you're envisioning to use this API. But I'll try:

I wonder if the level of abstraction is right. The patch assumes that the on-disk storage of all sequences is the same, so the access method can't change that. But then it leaves the details of actually updating the on-disk block, WAL-logging and all, as the responsibility of the access method. Surely that's going to look identical in all the seqams, if they all use the same on-disk format. That also means that the sequence access methods can't be implemented as plugins, as plugins can't do WAL-logging.

The comment in seqam.c says that there's a private column reserved for access method-specific data, called am_data, but that seems to be the only mention of am_data in the patch.

- Heikki

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