Re: New Event Trigger: table_rewrite

From: Dimitri Fontaine <dimitri(at)2ndQuadrant(dot)fr>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: New Event Trigger: table_rewrite
Date: 2014-11-07 12:35:10
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Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> It would be more useful to work on the applications of this....
> 1. INSERT into a table
> * Action start time
> * Schema
> * Tablename
> * Number of blocks in table
> which would then allow you to do these things run an assessment report
> showing which tables would be rewritten.

That should be done by the user, from within his Event Trigger code. For
that to be possible, the previous patch was missing a way to expose the
OID of the table being rewritten, I've now added support for that.

> 2. Get access to number of blocks, so you could limit rewrites only to
> smaller tables by putting a block limit in place.

Also, I did expand the docs to fully cover your practical use case of a
table_rewrite Event Trigger implementing such a table rewrite policy.

> 3. It might be even cooler to contemplate having pg_stat_activity
> publish an estimated end time.
> We'd probably need some kind of time_per_block parameter for each
> tablespace so we can estimate the time.

That feels like another patch entirely.

Dimitri Fontaine 06 63 07 10 78 PostgreSQL : Expertise, Formation et Support

Attachment Content-Type Size
table_rewrite.2.patch text/x-patch 58.1 KB

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