Horton

Re: row filtering for logical replication

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Ajin Cherian <itsajin@gmail.com>
Cc: Euler Taveira <euler@eulerto.com>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Greg Nancarrow <gregn4422@gmail.com>, vignesh C <vignesh21@gmail.com>, Peter Smith <smithpb2250@gmail.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, Dilip Kumar <dilipbalaut@gmail.com>, Rahila Syed <rahilasyed90@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Önder Kalacı <onderkalaci@gmail.com>, japin <japinli@hotmail.com>, Michael Paquier <michael@paquier.xyz>, David Steele <david@pgmasters.net>, Craig Ringer <craig@2ndquadrant.com>, Amit Langote <amitlangote09@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-12-21T06:19:17Z
Lists: pgsql-hackers

Commits

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  1. Release cache tuple when no longer needed

  2. Add some additional tests for row filters in logical replication.

  3. Fix one of the tests introduced in commit 52e4f0cd47.

  4. Allow specifying row filters for logical replication of tables.

  5. Move scanint8() to numutils.c

  6. Replace Test::More plans with done_testing

  7. Reduce relcache access in WAL sender streaming logical changes

  8. Small cleanups related to PUBLICATION framework code

  9. Add a view to show the stats of subscription workers.

  10. Allow publishing the tables of schema.

  11. Doc: improve documentation of CREATE/ALTER SUBSCRIPTION.

  12. Add PublicationTable and PublicationRelInfo structs

  13. Remove unused argument "txn" in maybe_send_schema().

  14. Add prepare API support for streaming transactions in logical replication.

  15. Unify PostgresNode's new() and get_new_node() methods

  16. Use l*_node() family of functions where appropriate

  17. Add support for prepared transactions to built-in logical replication.

  18. Restore the portal-level snapshot after procedure COMMIT/ROLLBACK.

  19. Rename a parse node to be more general

  20. Remove unused column atttypmod from initial tablesync query

  21. SEARCH and CYCLE clauses

On Tue, Dec 21, 2021 at 6:17 AM Ajin Cherian <itsajin@gmail.com> wrote:
>
> On Tue, Dec 21, 2021 at 5:58 AM Euler Taveira <euler@eulerto.com> wrote:
> >
> >In pgoutput_row_filter_update(), first, we are deforming the tuple in
> >local datum, then modifying the tuple, and then reforming the tuple.
> >I think we can surely do better here. Currently, you are reforming
> >the tuple so that you can store it in the scan slot by calling
> >ExecStoreHeapTuple which will be used for expression evaluation.
> >Instead of that what you need to do is to deform the tuple using
> >tts_values of the scan slot and later call ExecStoreVirtualTuple(), so
> >advantages are 1) you don't need to reform the tuple 2) the expression
> >evaluation machinery doesn't need to deform again for fetching the
> >value of the attribute, instead it can directly get from the value
> >from the virtual tuple.
>
> Storing the old tuple/new tuple in a slot and re-using the slot avoids
> the overhead of
> continuous deforming of tuple at multiple levels in the code.
>

Yeah, deforming tuples again can have a significant cost but what is
the need to maintain tmp_new_tuple in relsyncentry. I think that is
required in rare cases, so we can probably allocate/deallocate when
required.

Few other comments:
==================
1.
  TupleTableSlot *scantuple; /* tuple table slot for row filter */
+ TupleTableSlot *new_tuple; /* slot for storing deformed new tuple
during updates */
+ TupleTableSlot *old_tuple; /* slot for storing deformed old tuple
during updates */

I think it is better to name these as scan_slot, new_slot, old_slot to
avoid confusion with tuples.

2.
+++ b/src/backend/replication/logical/proto.c
@@ -19,6 +19,7 @@
 #include "replication/logicalproto.h"
 #include "utils/lsyscache.h"
 #include "utils/syscache.h"
+#include "executor/executor.h"

The include is in wrong order. We keep includes in alphabatic order.

3.
@@ -832,6 +847,7 @@ logicalrep_write_tuple(StringInfo out, Relation
rel, HeapTuple tuple, bool binar

  ReleaseSysCache(typtup);
  }
+
 }

Spurious addition.

4.
-logicalrep_write_tuple(StringInfo out, Relation rel, HeapTuple tuple,
bool binary)
+logicalrep_write_tuple(StringInfo out, Relation rel, HeapTuple tuple,
TupleTableSlot *slot,
+bool binary)

The formatting is quite off. Please run pgindent.

5. If we decide to go with this approach then I feel let's merge the
required comments from Euler's version.



-- 
With Regards,
Amit Kapila.