Re: Enabling Checksums

On Tue, 2012-11-13 at 15:27 -0500, Robert Haas wrote:
> A small
> patch that gets committed is better than a big one that doesn't.

Here's a small patch (two, actually, because the TLI one is
uninteresting and noisy). It's based on Simon's patch, but with some
significant changes:

  * I ripped out all of the handling for a mix of some checksummed and
some non-checksummed pages. No more control bits or page version stuff.
  * I moved the checksum to the pd_tli field, and renamed it
pd_checksum.
  * vm/fsm_extend were not setting the verification information for some
reason. I'm not sure why, but since it's now on/off for the entire
system, they need to do the same thing.
  * Added a flag to pg_control called data_checksums. It is set by
initdb when the "-k"/"--data-checksums" option is specified (open for
discussion).
  * Added a function in xlog.c that is a simple reader of the control
file flag.
  * Got rid of page_checksums GUC.
  * Incorporated the page number into the checksum calculation, to
detect pages that are transposed.

I'll do another pass to make sure I update all of the comments, and try
to self review it. So, slightly rough in some places.

Regards,
    Jeff Davis