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: 2020-05-22T12:51:36Z
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.

Attachments

On Mon, May 18, 2020 at 5:57 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Mon, May 18, 2020 at 4:10 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Sun, May 17, 2020 at 12:41 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > >
>
> Few comments on v20-0010-Bugfix-handling-of-incomplete-toast-tuple
> 1.
> + /*
> + * If this is a toast insert then set the corresponding bit.  Otherwise, if
> + * we have toast insert bit set and this is insert/update then clear the
> + * bit.
> + */
> + if (toast_insert)
> + toptxn->txn_flags |= RBTXN_HAS_TOAST_INSERT;
> + else if (rbtxn_has_toast_insert(txn) &&
> + ChangeIsInsertOrUpdate(change->action))
> + {
>
> Here, it might better to add a comment on why we expect only
> Insert/Update?  Also, it might be better that we add an assert for
> other operations.

I have added comments that why on Insert/Update we clean the flag.
But I don't think we only expect insert/update,  we might get the
toast delete right? because in toast update we will do toast delete +
toast insert.  So when we get toast delete we just don't want to do
anything.

>
> 2.
> @@ -1865,8 +1920,8 @@ ReorderBufferProcessTXN(ReorderBuffer *rb,
> ReorderBufferTXN *txn,
>   * disk.
>   */
>   dlist_delete(&change->node);
> - ReorderBufferToastAppendChunk(rb, txn, relation,
> -   change);
> + ReorderBufferToastAppendChunk(rb, txn, relation,
> +   change);
>   }
>
> This seems to be a spurious change.

Done

> 3.
> + /*
> + * If streaming is enable and we have serialized this transaction because
> + * it had incomplete tuple.  So if now we have got the complete tuple we
> + * can stream it.
> + */
> + if (ReorderBufferCanStream(rb) && can_stream && rbtxn_is_serialized(toptxn)
> + && !(rbtxn_has_toast_insert(txn)) && !(rbtxn_has_spec_insert(txn)))
> + {
>
> This comment is just saying what you are doing in the if-check.  I
> think you need to explain the rationale behind it. I don't like the
> variable name 'can_stream' because it matches ReorderBufferCanStream
> whereas it is for a different purpose, how about naming it as
> 'change_complete' or something like that.  The check has many
> conditions, can we move it to a separate function to make the code
> here look clean?

As per the other comments we have removed this part in the latest patch set.

Apart from these comments fixes, there are 2 more changes
1.  Handling of the toast tuple is changed as per the offlist
discussion with you
Basically, now, instead of not streaming the txn with the incomplete
tuple, we are streaming it up to the last complete lsn.  So of the txn
has incomplete changes but its complete size is largest then we will
stream this.  And, after streaming we will truncate the transaction up
to the last complete lsn.

2. There is a bug fix in handling the stream abort in 0008 (earlier it
was 0006).

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