Horton

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

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Dilip Kumar <dilipbalaut@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: 2020-06-24T11:08:34Z
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 24, 2020 at 4:27 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
>  iOn Wed, Jun 24, 2020 at 4:04 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Tue, Jun 23, 2020 at 7:00 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > >
> > > Here is the POC patch to discuss the idea of a cleanup of shared
> > > fileset on proc exit.  As discussed offlist,  here I am maintaining
> > > the list of shared fileset.  First time when the list is NULL I am
> > > registering the cleanup function with on_proc_exit routine.  After
> > > that for subsequent fileset, I am just appending it to filesetlist.
> > > There is also an interface to unregister the shared file set from the
> > > cleanup list and that is done by the caller whenever we are deleting
> > > the shared fileset manually.  While explaining it here, I think there
> > > could be one issue if we delete all the element from the list will
> > > become NULL and on next SharedFileSetInit we will again register the
> > > function.  Maybe that is not a problem but we can avoid registering
> > > multiple times by using some flag in the file
> > >
> >
> > I don't understand what you mean by "using some flag in the file".
>
> Basically, in POC as shown in below code snippet,  We are checking
> that if the "filesetlist" is NULL then only register the on_proc_exit
> function.  But, as described above if all the items are deleted the
> list will be NULL.  So I told that instead of checking the filesetlist
> is NULL,  we can have just a boolean variable that if we have
> registered the callback then don't do it again.
>

Check if there is any precedent of the same in the code?

>
> >
> > Review comments on various patches.
> >
> > poc_shared_fileset_cleanup_on_procexit
> > =================================
> > 1.
> > - ent->subxact_fileset =
> > - MemoryContextAlloc(ApplyContext, sizeof(SharedFileSet));
> > + MemoryContext oldctx;
> >
> > + /* Shared fileset handle must be allocated in the persistent context */
> > + oldctx = MemoryContextSwitchTo(ApplyContext);
> > + ent->subxact_fileset = palloc(sizeof(SharedFileSet));
> >   SharedFileSetInit(ent->subxact_fileset, NULL);
> > + MemoryContextSwitchTo(oldctx);
> >   fd = BufFileCreateShared(ent->subxact_fileset, path);
> >
> > Why is this change required for this patch and why we only cover
> > SharedFileSetInit in the Apply context and not BufFileCreateShared?
> > The comment is also not very clear on this point.
>
> Because only the sharedfileset and the filesetlist which is allocated
> under SharedFileSetInit, are required in the permanent context.
> BufFileCreateShared, only creates the Buffile and VFD which will be
> required only within the current stream so transaction context is
> enough.
>

Okay, then add some more comments to explain it or if you have
explained it elsewhere, then add a reference for the same.

> > 2.
> > +void
> > +SharedFileSetUnregister(SharedFileSet *input_fileset)
> > +{
> > + bool found = false;
> > + ListCell *l;
> > +
> > + Assert(filesetlist != NULL);
> > +
> > + /* Loop over all the pending shared fileset entry */
> > + foreach (l, filesetlist)
> > + {
> > + SharedFileSet *fileset = (SharedFileSet *) lfirst(l);
> > +
> > + /* remove the entry from the list and delete the underlying files */
> > + if (input_fileset->number == fileset->number)
> > + {
> > + SharedFileSetDeleteAll(fileset);
> > + filesetlist = list_delete_cell(filesetlist, l);
> >
> > Why are we calling SharedFileSetDeleteAll here when in the caller we
> > have already deleted the fileset as per below code?
> > BufFileDeleteShared(ent->stream_fileset, path);
> > + SharedFileSetUnregister(ent->stream_fileset);
> >
> > I think it will be good if somehow we can remove the fileset from
> > filesetlist during BufFileDeleteShared.  If that is possible, then we
> > don't need a separate API for SharedFileSetUnregister.
>
> But the filesetlist is maintained at the sharedfileset level, so even
> if we delete from BufFileDeleteShared, we need to call an API from the
> sharedfileset layer to unregister the fileset.
>

Sure, but isn't it better if we can call such an API from BufFileDeleteShared?


-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com