Horton

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

Kuntal Ghosh <kuntalghosh.2007@gmail.com>

View thread
From: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Amit Kapila <amit.kapila16@gmail.com>, Michael Paquier <michael@paquier.xyz>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-04-13T12:41:56Z
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 Mon, Apr 13, 2020 at 5:20 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> On Mon, Apr 13, 2020 at 4:14 PM Kuntal Ghosh <kuntalghosh.2007@gmail.com> wrote:
> >
> > +#define SizeOfTransactionId (sizeof(TransactionId) + sizeof(char))
> > This looks wrong. We should change the name of this Macro or we can
> > add the 1 byte directly in HEADER_SCRATCH_SIZE and some comments.
>
> I think this is in sync with below code (SizeOfXlogOrigin),  SO doen't
> make much sense to add different terminology no?
> #define SizeOfXlogOrigin (sizeof(RepOriginId) + sizeof(char))
> +#define SizeOfTransactionId (sizeof(TransactionId) + sizeof(char))
>
In that case, we can rename this, for example, SizeOfXLogTransactionId.

Some review comments from 0002-Issue-individual-*.path,

+void
+ReorderBufferAddInvalidation(ReorderBuffer *rb, TransactionId xid,
+ XLogRecPtr lsn, int nmsgs,
+ SharedInvalidationMessage *msgs)
+{
+ MemoryContext oldcontext;
+ ReorderBufferChange *change;
+
+ /* XXX Should we even write invalidations without valid XID? */
+ if (xid == InvalidTransactionId)
+ return;
+
+ Assert(xid != InvalidTransactionId);

It seems we don't call the function if xid is not valid. In fact,

@@ -281,6 +281,24 @@ DecodeXactOp(LogicalDecodingContext *ctx,
XLogRecordBuffer *buf)
  }
  case XLOG_XACT_ASSIGNMENT:
  break;
+ case XLOG_XACT_INVALIDATIONS:
+ {
+ TransactionId xid;
+ xl_xact_invalidations *invals;
+
+ xid = XLogRecGetXid(r);
+ invals = (xl_xact_invalidations *) XLogRecGetData(r);
+
+ if (!TransactionIdIsValid(xid))
+ break;
+
+ ReorderBufferAddInvalidation(reorder, xid, buf->origptr,
+ invals->nmsgs, invals->msgs);

Why should we insert an WAL record for such cases?

+ * When wal_level=logical, write invalidations into WAL at each command end to
+ *  support the decoding of the in-progress transaction.  As of now it was
+ *  enough to log invalidation only at commit because we are only decoding the
+ *  transaction at the commit time.   We only need to log the catalog cache and
+ *  relcache invalidation.  There can not be any active MVCC scan in logical
+ *  decoding so we don't need to log the snapshot invalidation.
The alignment is not right.

 /*
  * CommandEndInvalidationMessages
- * Process queued-up invalidation messages at end of one command
- * in a transaction.
+ *              Process queued-up invalidation messages at end of one command
+ *              in a transaction.
Looks unnecessary changes.

  * Note:
- * This should be called during CommandCounterIncrement(),
- * after we have advanced the command ID.
+ *              This should be called during CommandCounterIncrement(),
+ *              after we have advanced the command ID.
  */
Looks unnecessary changes.

  if (transInvalInfo == NULL)
- return;
+ return;
Looks unnecessary changes.

+ /* prepare record */
+ memset(&xlrec, 0, sizeof(xlrec));
We should use MinSizeOfXactInvalidations, no?

-- 
Thanks & Regards,
Kuntal Ghosh
EnterpriseDB: http://www.enterprisedb.com