Re: Proposal: Adding compression of temporary files

Hello!

I tried to review the code. It compiled, the test suite passed.

I noticed two typos:

buffile.c:77 - "Disaled"
buffile.c:133 - "mathods"

And a few other small findings:

buffile.h:35 and buffile.c:63 - same constants defined first as an
Enum and then as #defines - code builds properly without the defines.

buffile.c:121 - compress_tempfile is defined, set to false at :167,
but never used otherwise

guc_tables.c:470 - the comment says that pglz isn't supported yet, but
we have a value for it, and I see support for it in the code

buffile.c:659: (and at other places) if USE_LZ4 is undefined, the
codepath doesn't do anything. I think these ifdefs should follow how
other compression code works, such as wal compression where there's an
#else path with elog(ERROR, ...)
Similarly, maybe there should be an explicit TEMP_NONE_COMPRESSION
branch that does nothing, and the default branch should be an error?

buffile.c:265: If seek isn't supported/limited, shouldn't there be at
least an assertion about it in BufFileSeek? And tell isn't mentioned,
but it seems to me that tell also doesn't work properly.