Re: PITR, checkpoint, and local relations

Christopher Kings-Lynne wrote:
> > The main area where it seems to get heavy use is during index builds,
> > and for 'CREATE TABLE AS SELECT...'.
> >
> > So I will remove the local buffer manager as part of the PITR patch,
> > unless there is further objection.
>
> Would someone mind filling me in as to what the local bugger manager is and
> how it is different (and not useful) compared to the shared buffer manager?

Sure. I think I can handle that.

When you create a table in a transaction, there isn't any committed
state to the table yet, so any table modifications are kept in a local
buffer, which is local memory to the backend(?). No one needs to see it
because it isn't visible to anyone yet. Same for indexes.

Anyway, the WAL activity doesn't handle local buffers the same as shared
buffers because there is no crisis if the system crashes.

There is debate on whether the local buffers are even valuable
considering the headache they cause in other parts of the system.

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