Re: trying again to get incremental backup

0001 looks OK to push, and since it stands on its own I would get it out
of the way soon rather than waiting for the rest of the series to be
further reviewed.

0002:
This moves bin/pg_verifybackup/parse_manifest.c to
common/parse_manifest.c, where it's not clear that it's for backup
manifests (wasn't a problem in the previous location). I wonder if
we're going to have anything else called "manifest", in which case I
propose to rename the file to make it clear that this is about backup
manifests -- maybe parse_bkp_manifest.c.

This patch looks pretty uncontroversial, but there's no point in going
further with this one until followup patches are closer to commit.

0003:
AmWalSummarizerProcess() is unused. Remove?

MaybeWalSummarizer() is called on each ServerLoop() in postmaster.c?
This causes a function call to be emitted every time through. That
looks odd. All other process starts have some triggering condition.

GetOldestUnsummarizedLSN uses while(true), but WaitForWalSummarization
and SummarizeWAL use while(1). Maybe settle on one style?

Still reading this one.

0004:
in PrepareForIncrementalBackup(), the logic that determines
earliest_wal_range_tli and latest_wal_range_tli looks pretty weird. I
think it works fine if there's a single timeline, but not otherwise.
Or maybe the trick is that it relies on timelines returned by
readTimeLineHistory being sorted backwards? If so, maybe add a comment
about that somewhere; I don't think other callers of readTimeLineHistory
make that assumption.

--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"Postgres is bloatware by design: it was built to house
PhD theses." (Joey Hellerstein, SIGMOD annual conference 2002)