Avoid copying WAL segments before divergence to speed up pg_rewind #8
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This optimization adds a conditional check to avoid unnecessarily copying WAL segment files from source to target if they are common between both servers, before the point of WAL divergence during pg_rewind. On the source server, each WAL file's corresponding segment number is computed and compared against the segment number of the first diverged LSN. All WAL files which fall before the segment of the first diverged LSN can safely be skipped from copying to the target. The reduction in WAL segment files transmitted over the network from source to target server massively reduces overall pg_rewind execution time when a large amount of WAL segment files are retained. Regression tests are included to verify that WAL segment files prior to WAL divergence are not copied. Authors: Justin Kwan, Vignesh Ravichandran
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This optimization adds a conditional check to avoid unnecessarily copying WAL segment files from source to target if they are common between both servers, before the point of WAL divergence during pg_rewind.
On the source server, each WAL file's corresponding segment number is computed and compared against the segment number of the first diverged LSN. All WAL files which fall before the segment of the first diverged LSN can safely be skipped from copying to the target.
The reduction in WAL segment files transmitted over the network from source to target server massively reduces overall pg_rewind execution time when a large amount of WAL segment files are retained.
Regression tests are included to verify that WAL segment files prior to WAL divergence are not copied.
Authors: Justin Kwan, Vignesh Ravichandran