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: 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: 2020-05-28T07:27:29Z
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 Tue, May 26, 2020 at 3:04 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Mon, May 25, 2020 at 8:07 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> >
> > On Fri, May 22, 2020 at 11:54 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> > > 4.
> > > + * XXX Do we need to allocate it in TopMemoryContext?
> > > + */
> > > +static void
> > > +subxact_info_add(TransactionId xid)
> > > {
> > > ..
> > >
> > > For this and other places in a patch like in function
> > > stream_open_file(), instead of using TopMemoryContext, can we consider
> > > using a new memory context LogicalStreamingContext or something like
> > > that. We can create LogicalStreamingContext under TopMemoryContext.  I
> > > don't see any need of using TopMemoryContext here.
> >
> > But, when we will delete/reset the LogicalStreamingContext?
> >
>
> Why can't we reset it at each stream stop message?
> >  because
> > we are planning to keep this memory until the worker is alive so that
> > supposed to be the top memory context.
> >
>
> Which part of allocation do we want to keep till the worker is alive?

static TransactionId *xids = NULL; we need to keep till worker life space.

> Why we need memory-related to subxacts till the worker is alive?  As
> we have now, after reading subxact info (subxact_info_read), we need
> to ensure that it is freed after its usage due to which we need to
> remember and perform pfree at various places.
>
> I think we should once see the possibility that such that we could
> switch to this new context in start stream message and reset it in
> stop stream message.  That might help in avoiding
> MemoryContextSwitchTo TopMemoryContext at various places.

Ok, I understand, I think subxacts can be allocated in new
LogicalStreamingContext which we can reset at the stream stop.  How
about xids?
shall we create another context that will stay until the worker lifespan?

> >  If we create any other context
> > with the same life span as TopMemoryContext then what is the point?
>>
>
> It is helpful for debugging.  It is recommended that we don't use the
> top memory context unless it is really required.  Read about it in
> src/backend/utils/mmgr/README.

I see.

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