Re: Undo logs

On 24 May 2018 at 23:22, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> wrote:

> As announced elsewhere[1][2][3], at EnterpriseDB we are working on a
> proposal to add in-place updates with undo logs to PostgreSQL. The
> goal is to improve performance and resource usage by recycling space
> better.

Cool

> The lowest level piece of this work is a physical undo log manager,

> 1. Efficient appending of new undo data from many concurrent
> backends. Like logs.
> 2. Efficient discarding of old undo data that isn't needed anymore.
> Like queues.
> 3. Efficient buffered random reading of undo data. Like relations.

Like an SLRU?

> [4] https://github.com/EnterpriseDB/zheap/tree/undo-log-storage/src/backend/access/undo
> [5] https://github.com/EnterpriseDB/zheap/tree/undo-log-storage/src/backend/storage/smgr

I think there are quite a few design decisions there that need to be
discussed, so lets crack on and discuss them please.

--
Simon Riggs http://www.2ndQuadrant.com/
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