Attempt to consolidate reading of XLOG page

Antonin Houska <ah@cybertec.at>

From: Antonin Houska <ah@cybertec.at>

To: pgsql-hackers@postgresql.org

Date: 2019-04-11T16:05:42Z

Lists: pgsql-hackers

Attachments

reuse_xlogread.patch (text/x-diff) patch

While working on the instance encryption I found it annoying to apply
decyption of XLOG page to three different functions. Attached is a patch that
tries to merge them all into one function, XLogRead(). The existing
implementations differ in the way new segment is opened. So I added a pointer
to callback function as a new argument. This callback handles the specific
ways to determine segment file name and to open the file.

I can split the patch into multiple diffs to make detailed review easier, but
first I'd like to hear if anything is seriously wrong about this
design. Thanks.

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com

Commits

Remove logical_read_local_xlog_page
- 5d0c2d5eba6b 13.0 landed
Refactor WAL file-reading code into WALRead()
- 0dc8ead46363 13.0 landed
Rework WAL-reading supporting structs
- 709d003fbd98 13.0 landed
Make XLogReaderInvalReadState static
- 25dcc9d35dfe 13.0 landed
Use pg_pread() and pg_pwrite() for data files and WAL.
- c24dcd0cfd94 12.0 cited