Re: WAL/PITR additional items

Should any of these be added to TODO?

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Simon Riggs wrote:
> A range of WAL/PITR items still need work. I'm fairly sure I won't be
> doing any of these in time for 8.1, so feel free to have a go.
>
> 1. PITR archive recovery could do more to overlap recovery of files, so
> that recovery overall is faster. This is already possible by designing
> your archive command to perform this buffering for you, but it may be a
> good idea to build this directly into the recovery scheme.
>
> 2. PreallocXlogFiles to run from a separate process to make it
> effective, as discussed last year. The most natural place to put it
> would be the Archiver, though that is only present when archive_command
> is set. That means we could have the bgwriter execute it every so often,
> perhaps every 5 or 10 cycles to avoid lock contention.
>
> 3. If PreallocXlogFiles becomes effective, it should be possible to turn
> a pg_xlog directory out of space PANIC into a checkpoint to recycle
> outstanding WAL files, then retry the prealloc. If that helps then reset
> checkpoint_segments (and issue a WARNING to say it has happened) so that
> the out of space condition is not encountered again.
>
> 4. CRC reduction to CRC-32, plus hardware tuning. I'll stay in touch
> with that in case we have further information to tune the assembler.
>
> 5. WAL archive compression
>
> 6. xlog.c refactoring into two pieces: WAL writing and WAL recovery
>
> Best Regards, Simon Riggs
>
>
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