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 systems. New command options on end of statement allow syntax CREATE SEQUENCE foo_seq USING globalseqProduction 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.
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