For consistency with the existing code , how about renaming the macro XLR_BLCK_COMPRESSED_MASK as BKPBLOCK_HAS_COMPRESSED_IMAGE on the lines of BKPBLOCK_HAS_IMAGE.
Here , I think that having the mask as BKPBLOCK_HOLE_OFFSET_MASK will be more indicative of the fact that lower 15 bits of extra_data field comprises of hole_offset value. This suggestion is also just to achieve consistency with the existing BKPBLOCK_FORK_MASK for fork_flags field.
Yeah that seems clearer, let's define it as ~XLR_BLCK_COMPRESSED_MASK though.
And comment typo
+ * First try to compress block, filling in the page hole with zeros
+ * to improve the compression of the whole. If the block is considered
+ * as incompressible, complete the block header information as if
+ * nothing happened.
As hole is no longer being compressed, this needs to be changed.
Fixed. As well as an additional comment block down.
A couple of things noticed on the fly:
- Fixed pg_xlogdump being not completely correct to report the FPW information
- A couple of typos and malformed sentences fixed
- Added an assertion to check that the hole offset value does not the bit used for compression status
- Reworked docs, mentioning as well that wal_compression is off by default.
- Removed stuff in pg_controldata and XLOG_PARAMETER_CHANGE (mentioned by Fujii-san)
