Horton

Re: PATCH: logical_work_mem and logical streaming of large in-progress transactions

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Erik Rijkers <er@xs4all.nl>, Kuntal Ghosh <kuntalghosh.2007@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Michael Paquier <michael@paquier.xyz>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-06-04T08:35:09Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Tighten the concurrent abort check during decoding.

  2. Improve hash_create()'s API for some added robustness.

  3. Use HASH_BLOBS for xidhash.

  4. Fix initialization of RelationSyncEntry for streaming transactions.

  5. Remove unused function declaration in logicalproto.h.

  6. Add additional tests to test streaming of in-progress transactions.

  7. Fix inline marking introduced in commit 464824323e.

  8. Add support for streaming to built-in logical replication.

  9. Fix the SharedFileSetUnregister API.

  10. Fix comment in procarray.c

  11. Suppress compiler warning in non-cassert builds.

  12. Extend the BufFile interface.

  13. Mark a few logical decoding related variables with PGDLLIMPORT.

  14. Implement streaming mode in ReorderBuffer.

  15. Extend the logical decoding output plugin API with stream methods.

  16. WAL Log invalidations at command end with wal_level=logical.

  17. Immediately WAL-log subtransaction and top-level XID association.

  18. Allow logical replication to transfer data in binary format.

  19. Only superuser can set sslcert/sslkey in postgres_fdw user mappings

  20. Track statistics for spilling of changes from ReorderBuffer.

  21. Add logical_decoding_work_mem to limit ReorderBuffer memory usage.

  22. logical decoding: process ASSIGNMENT during snapshot build

  23. Emit invalidations to standby for transactions without xid.

On Wed, Jun 3, 2020 at 2:43 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Tue, Jun 2, 2020 at 7:53 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> >
> > On Tue, Jun 2, 2020 at 4:56 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> > > On Tue, Jun 2, 2020 at 3:59 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > > >
> > > > I thin for our use case BufFileCreateShared is more suitable.  I think
> > > > we need to do some modifications so that we can use these apps without
> > > > SharedFileSet. Otherwise, we need to unnecessarily need to create
> > > > SharedFileSet for each transaction and also need to maintain it in xid
> > > > array or xid hash until transaction commit/abort.  So I suggest
> > > > following modifications in shared files set so that we can
> > > > conveniently use it.
> > > > 1. ChooseTablespace(const SharedFileSet fileset, const char name)
> > > >   if fileset is NULL then select the DEFAULTTABLESPACEOID
> > > > 2. SharedFileSetPath(char path, SharedFileSet fileset, Oid tablespace)
> > > > If fileset is NULL then in directory path we can use MyProcPID or
> > > > something instead of fileset->creator_pid.
> > > >
> > >
> > > Hmm, I find these modifications a bit ad-hoc.  So, not sure if it is
> > > better than the patch maintains sharedfileset information.
> >
> > I think we might do something better here, maybe by supplying function
> > pointer or so,  but maintaining sharedfileset which contains different
> > tablespace/mutext which we don't need at all for our purpose also
> > doesn't sound very appealing.
> >
>
> I think we can say something similar for Relation (rel cache entry as
> well) maintained in LogicalRepRelMapEntry.  I think we only need a
> pointer to that information.

Yeah, I see.

> >  Let me see if I can not come up with
> > some clean way of avoiding the need to shared-fileset then maybe we
> > can go with the shared fileset idea.
> >
>
> Fair enough.

While evaluating it further I feel there are a few more problems to
solve if we are using BufFile,  First thing is that in subxact file we
maintain the information of xid and its offset in the changes file.
So now, we will also have to store 'fileno' but that we can find using
BufFileTell.  Yet another problem is that currently, we don't
have the truncate option in the BufFile,  but we need it if the
sub-transaction gets aborted.  I think we can implement an extra
interface with the BufFile and should not be very hard as we already
know the fileno and the offset.  I will evaluate this part further and
let you know about the same.

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