Re: [PATCH] add concurrent_abort callback for output plugin

[Markus Wanner]

On 30.03.21 11:12, Ajin Cherian wrote:
I found some documentation that already was talking about concurrent 
aborts and updated that.

Thanks.

I just noticed as of PG13, concurrent_abort is part of ReorderBufferTXN, 
so it seems the prepare_cb (or stream_prepare_cb) can actually figure a 
concurrent abort happened (and the transaction may be incomplete). 
That's good and indeed makes an additional callback unnecessary.

I recommend giving a hint to that field in the documentation as well.

diff --git a/doc/src/sgml/logicaldecoding.sgml 
b/doc/src/sgml/logicaldecoding.sgml
index 80eb96d..d2f8d39 100644
--- a/doc/src/sgml/logicaldecoding.sgml
+++ b/doc/src/sgml/logicaldecoding.sgml
@@ -545,12 +545,14 @@ CREATE TABLE another_catalog_table(data text) WITH 
(user_catalog_table = true);
      executed within that transaction. A transaction that is prepared for
      a two-phase commit using <command>PREPARE TRANSACTION</command> will
      also be decoded if the output plugin callbacks needed for decoding
-     them are provided. It is possible that the current transaction which
+     them are provided. It is possible that the current prepared transaction 
which
      is being decoded is aborted concurrently via a <command>ROLLBACK 
PREPARED</command>
      command. In that case, the logical decoding of this transaction will
-     be aborted too. We will skip all the changes of such a transaction once
-     the abort is detected and abort the transaction when we read WAL for
-     <command>ROLLBACK PREPARED</command>.
+     be aborted too. All the changes of such a transaction is skipped once

typo: changes [..] *are* skipped, plural.

+     the abort is detected and the <function>prepare_cb</function> callback is 
invoked.
+     This could result in a prepared transaction with incomplete changes.

... "in which case the <literal>concurrent_abort</literal> field of the 
passed <literal>ReorderBufferTXN</literal> struct is set.", as a proposal?

+     This is done so that eventually when the <command>ROLLBACK 
PREPARED</command>
+     is decoded, there is a corresponding prepared transaction with a matching 
gid.
     </para>
 
     <note>

Everything else sounds good to me.

Regards

Markus