Horton

Re: Make relfile tombstone files conditional on WAL level

Dilip Kumar <dilipbalaut@gmail.com>

View thread View on postgr.es
From: Dilip Kumar <dilipbalaut@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Heikki Linnakangas <hlinnaka@iki.fi>, Thomas Munro <thomas.munro@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-01-06T08:13:27Z
Lists: pgsql-hackers 
On Thu, Jan 6, 2022 at 1:12 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> >
> > I think this idea is worth more consideration. It seems like 2^56
> > relfilenodes ought to be enough for anyone, recalling that you can
> > only ever have 2^64 bytes of WAL. So if we do this, we can eliminate a
> > bunch of code that is there to guard against relfilenodes being
> > reused. In particular, we can remove the code that leaves a 0-length
> > tombstone file around until the next checkpoint to guard against
> > relfilenode reuse.
>
> +1
>

I IMHO a few top level point for implementing this idea would be as listed here,

1) the "relfilenode" member inside the RelFileNode will be now 64
bytes and remove the "forkNum" all together from the BufferTag.  So
now whenever we want to use the relfilenode or fork number we can use
the respective mask and fetch their values.
2) GetNewRelFileNode() will not loop for checking the file existence
and retry with other relfilenode.
3) Modify mdunlinkfork() so that we immediately perform the unlink
request, make sure to register_forget_request() before unlink.
4) In checkpointer, now we don't need any handling for pendingUnlinks.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Fix typos in comments, code and documentation

  2. Increase width of RelFileNumbers from 32 bits to 56 bits.

  3. Move RelFileNumber declarations to common/relpath.h.

  4. Include RelFileLocator fields individually in BufferTag.

  5. Convert macros to static inline functions (buf_internals.h)

  6. Remove the restriction that the relmap must be 512 bytes.

  7. Change internal RelFileNode references to RelFileNumber or RelFileLocator.

  8. Reorder subskiplsn in pg_subscription to avoid alignment issues.

  9. Fix DROP {DATABASE,TABLESPACE} on Windows.

  10. Restructure smgr API as per recent proposal. smgr no longer depends on