Re: corrupt pages detected by enabling checksums

On Fri, 2013-04-05 at 15:09 +0200, Andres Freund wrote:
> How does the attached version look? I verified that it survives
> recovery, but not more.

Comments:

* Regarding full page writes, we can:
- always write full pages (as in your current patch), regardless of
the current settings
- take WALInsertLock briefly to get the current settings from XLogCtl
- always calculate the full page record, but in XLogInsert, if it
happens to be a HINT record, and full page writes are not necessary,
then discard it (right now I somewhat favor this option but I haven't
looked at the details)

* typo in "Backup blocks are not used in **xlog xlog** records"

* To get the appropriate setting for buffer_std, we should pass it down
through MarkBufferDirty as an extra flag, I think.

* I'm a bit worried that we'll need a cleanup lock when restoring an FSM
page. What do you think?

* In xlog_redo, it seemed slightly awkward to call XLogRecGetData twice.
Merely a matter of preference but I thought I would mention it.

> Jeff, any chance you can run this for a round with your suite?

Yes. I don't have a rigorous test suite, but I'll do some manual tests
and walk through it with gdb.

Regards,
Jeff Davis