PostgreSQL 11 introduces configurable WAL segment sizes, from 1MB to 1GB.
There are two areas that needed to be updated to support this: building the archive-get queue and checking that WAL has been archived after a backup. Both operations require the WAL segment size to properly build a list.
Checking the archive after a backup is still implemented in Perl and has an active database connection, so just get the WAL segment size from the database.
The archive-get command does not have a connection to the database, so get the WAL segment size from pg_control instead. This requires a deeper inspection of pg_control than has been done in the past, so it seemed best to copy the relevant data structures from each version of PostgreSQL and build a generic interface layer to address them. While this approach is a bit verbose, it has the advantage of being relatively simple, and can easily be updated for new versions of PostgreSQL.
Since the integration tests generate pg_control files for testing, teach Perl how to generate files with the correct offsets for both 32-bit and 64-bit architectures.
The existing static files would not work with 32-bit or big-endian systems so create functions to generate these files dynamically rather than creating a bunch of new static files.
Refactor storage layer to allow for new repository filesystems using drivers. (Reviewed by Cynthia Shang.)
Refactor IO layer to allow for new compression formats, checksum types, and other capabilities using filters. (Reviewed by Cynthia Shang.)
