pgsql: Prevent archive recovery from scanning non-existent WAL files.

Prevent archive recovery from scanning non-existent WAL files.

Previously when there were multiple timelines listed in the history file
of the recovery target timeline, archive recovery searched all of them,
starting from the newest timeline to the oldest one, to find the segment
to read. That is, archive recovery had to continuously fail scanning
the segment until it reached the timeline that the segment belonged to.
These scans for non-existent segment could be harmful on the recovery
performance especially when archival area was located on the remote
storage and each scan could take a long time.

To address the issue, this commit changes archive recovery so that
it skips scanning the timeline that the segment to read doesn't belong to.

Author: Kyotaro Horiguchi, tweaked a bit by Fujii Masao
Reviewed-by: David Steele, Pavel Suderevsky, Grigory Smolkin
Discussion: https://postgr.es/m/16159-f5a34a3a04dc67e0@postgresql.org
Discussion: https://postgr.es/m/20200129.120222.1476610231001551715.horikyota.ntt@gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4bd0ad9e44be9fbc3ad77747d7672dab1c3df7d9

Modified Files
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src/backend/access/transam/xlog.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)