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From: Peter Smith <[email protected]>
To: Amit Kapila <[email protected]>
Cc: vignesh C <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Add macros for ReorderBufferTXN toptxn
Date: Wed, 15 Mar 2023 10:54:26 +1100
Message-ID: <CAHut+PtrD4xU4OPUB64ZK+DPDhfKn3zph=nDpEWUFFzUvMKo2w@mail.gmail.com> (raw)
In-Reply-To: <CAA4eK1LGFhOsqLhZfiHOvgmzzO5MHJ7OgQMnOCbYp6A9Ks92WQ@mail.gmail.com>
References: <CAHut+PuCznOyTqBQwjRUu-ibG-=KHyCv-0FTcWQtZUdR88umfg@mail.gmail.com>
	<CALDaNm1J-V06vNM1JBwP1OJgAQKWntJvfG8gf=3Kfnpm=bE-Yw@mail.gmail.com>
	<CAHut+PuRgxhk4GBK8Fm8hgDH=KLGvCjjOvcNXMapHgyN1bQfDA@mail.gmail.com>
	<CAA4eK1LGFhOsqLhZfiHOvgmzzO5MHJ7OgQMnOCbYp6A9Ks92WQ@mail.gmail.com>

On Tue, Mar 14, 2023 at 10:43 PM Amit Kapila <[email protected]> wrote:
>
> On Tue, Mar 14, 2023 at 12:37 PM Peter Smith <[email protected]> wrote:
> >
> > Thanks for the review!
> >
> > On Mon, Mar 13, 2023 at 6:19 PM vignesh C <[email protected]> wrote:
> > ...
> >
> > > 4) We check if txn->toptxn is not null twice here both in if condition
> > > and in the assignment, we could retain the assignment operation as
> > > earlier to remove the 2nd check:
> > > -       if (txn->toptxn)
> > > -               txn = txn->toptxn;
> > > +       if (isa_subtxn(txn))
> > > +               txn = get_toptxn(txn);
> > >
> > > We could avoid one check again by:
> > > +       if (isa_subtxn(txn))
> > > +               txn = txn->toptxn;
> > >
> >
> > Yeah, that is true, but I chose not to keep the original assignment in
> > this case mainly because then it is consistent with the other changed
> > code ---  e.g. Every other direct member assignment/access of the
> > 'toptxn' member now hides behind the macros so I did not want this
> > single place to be the odd one out. TBH, I don't think 1 extra check
> > is of any significance, but it is not a problem to change like you
> > suggested if other people also want it done that way.
> >
>
> Can't we directly use rbtxn_get_toptxn() for this case? I think that
> way code will look neat. I see that it is not exactly matching the
> existing check so you might be worried but I feel the new code will
> achieve the same purpose and will be easy to follow.
>

OK. Done as suggested.

PSA v3.

------
Kind Regards,
Peter Smith.
Fujitsu Australia


Attachments:

  [application/octet-stream] v3-0001-Add-macros-for-ReorderBufferTXN-toptxn.patch (6.4K, ../CAHut+PtrD4xU4OPUB64ZK+DPDhfKn3zph=nDpEWUFFzUvMKo2w@mail.gmail.com/2-v3-0001-Add-macros-for-ReorderBufferTXN-toptxn.patch)
  download | inline diff:
From 9b660e136afa6f820af3c3d27841ece4e021121e Mon Sep 17 00:00:00 2001
From: Peter Smith <[email protected]>
Date: Wed, 15 Mar 2023 09:37:20 +1100
Subject: [PATCH v3] Add macros for ReorderBufferTXN toptxn.

Make toptxn related code more readable by introducing some simple macros.
---
 contrib/test_decoding/test_decoding.c           |  4 +--
 src/backend/replication/logical/reorderbuffer.c | 40 ++++++++++---------------
 src/backend/replication/pgoutput/pgoutput.c     |  6 ++--
 src/include/replication/reorderbuffer.h         | 18 +++++++++++
 4 files changed, 38 insertions(+), 30 deletions(-)

diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index b7e6048..628c6a2 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -815,11 +815,11 @@ pg_decode_stream_abort(LogicalDecodingContext *ctx,
 	 * maintain the output_plugin_private only under the toptxn so if this is
 	 * not the toptxn then fetch the toptxn.
 	 */
-	ReorderBufferTXN *toptxn = txn->toptxn ? txn->toptxn : txn;
+	ReorderBufferTXN *toptxn = rbtxn_get_toptxn(txn);
 	TestDecodingTxnData *txndata = toptxn->output_plugin_private;
 	bool		xact_wrote_changes = txndata->xact_wrote_changes;
 
-	if (txn->toptxn == NULL)
+	if (rbtxn_is_toptxn(txn))
 	{
 		Assert(txn->output_plugin_private != NULL);
 		pfree(txndata);
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 2d17c55..0f063b0 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -717,10 +717,7 @@ ReorderBufferProcessPartialChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
 		return;
 
 	/* Get the top transaction. */
-	if (txn->toptxn != NULL)
-		toptxn = txn->toptxn;
-	else
-		toptxn = txn;
+	toptxn = rbtxn_get_toptxn(txn);
 
 	/*
 	 * Indicate a partial change for toast inserts.  The change will be
@@ -809,13 +806,7 @@ ReorderBufferQueueChange(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn,
 		change->action == REORDER_BUFFER_CHANGE_TRUNCATE ||
 		change->action == REORDER_BUFFER_CHANGE_MESSAGE)
 	{
-		ReorderBufferTXN *toptxn;
-
-		/* get the top transaction */
-		if (txn->toptxn != NULL)
-			toptxn = txn->toptxn;
-		else
-			toptxn = txn;
+		ReorderBufferTXN *toptxn = rbtxn_get_toptxn(txn);
 
 		toptxn->txn_flags |= RBTXN_HAS_STREAMABLE_CHANGE;
 	}
@@ -1667,7 +1658,7 @@ ReorderBufferTruncateTXN(ReorderBuffer *rb, ReorderBufferTXN *txn, bool txn_prep
 	 * about the toplevel xact (we send the XID in all messages), but we never
 	 * stream XIDs of empty subxacts.
 	 */
-	if ((!txn_prepared) && ((!txn->toptxn) || (txn->nentries_mem != 0)))
+	if ((!txn_prepared) && (rbtxn_is_toptxn(txn) || (txn->nentries_mem != 0)))
 		txn->txn_flags |= RBTXN_IS_STREAMED;
 
 	if (txn_prepared)
@@ -3207,10 +3198,7 @@ ReorderBufferChangeMemoryUpdate(ReorderBuffer *rb,
 	 * Update the total size in top level as well. This is later used to
 	 * compute the decoding stats.
 	 */
-	if (txn->toptxn != NULL)
-		toptxn = txn->toptxn;
-	else
-		toptxn = txn;
+	toptxn = rbtxn_get_toptxn(txn);
 
 	if (addition)
 	{
@@ -3295,8 +3283,7 @@ ReorderBufferAddInvalidations(ReorderBuffer *rb, TransactionId xid,
 	 * so that we can execute them all together.  See comments atop this
 	 * function.
 	 */
-	if (txn->toptxn)
-		txn = txn->toptxn;
+	txn = rbtxn_get_toptxn(txn);
 
 	Assert(nmsgs > 0);
 
@@ -3354,7 +3341,6 @@ ReorderBufferXidSetCatalogChanges(ReorderBuffer *rb, TransactionId xid,
 								  XLogRecPtr lsn)
 {
 	ReorderBufferTXN *txn;
-	ReorderBufferTXN *toptxn;
 
 	txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
 
@@ -3370,11 +3356,15 @@ ReorderBufferXidSetCatalogChanges(ReorderBuffer *rb, TransactionId xid,
 	 * conveniently check just top-level transaction and decide whether to
 	 * build the hash table or not.
 	 */
-	toptxn = txn->toptxn;
-	if (toptxn != NULL && !rbtxn_has_catalog_changes(toptxn))
+	if (rbtxn_is_subtxn(txn))
 	{
-		toptxn->txn_flags |= RBTXN_HAS_CATALOG_CHANGES;
-		dclist_push_tail(&rb->catchange_txns, &toptxn->catchange_node);
+		ReorderBufferTXN *toptxn = rbtxn_get_toptxn(txn);
+
+		if (!rbtxn_has_catalog_changes(toptxn))
+		{
+			toptxn->txn_flags |= RBTXN_HAS_CATALOG_CHANGES;
+			dclist_push_tail(&rb->catchange_txns, &toptxn->catchange_node);
+		}
 	}
 }
 
@@ -3619,7 +3609,7 @@ ReorderBufferCheckMemoryLimit(ReorderBuffer *rb)
 			(txn = ReorderBufferLargestStreamableTopTXN(rb)) != NULL)
 		{
 			/* we know there has to be one, because the size is not zero */
-			Assert(txn && !txn->toptxn);
+			Assert(txn && rbtxn_is_toptxn(txn));
 			Assert(txn->total_size > 0);
 			Assert(rb->size >= txn->total_size);
 
@@ -4007,7 +3997,7 @@ ReorderBufferStreamTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
 	bool		txn_is_streamed;
 
 	/* We can never reach here for a subtransaction. */
-	Assert(txn->toptxn == NULL);
+	Assert(rbtxn_is_toptxn(txn));
 
 	/*
 	 * We can't make any assumptions about base snapshot here, similar to what
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index 00a2d73..3a2d2e3 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -694,8 +694,8 @@ maybe_send_schema(LogicalDecodingContext *ctx,
 	if (in_streaming)
 		xid = change->txn->xid;
 
-	if (change->txn->toptxn)
-		topxid = change->txn->toptxn->xid;
+	if (rbtxn_is_subtxn(change->txn))
+		topxid = rbtxn_get_toptxn(change->txn)->xid;
 	else
 		topxid = xid;
 
@@ -1879,7 +1879,7 @@ pgoutput_stream_abort(struct LogicalDecodingContext *ctx,
 	Assert(!in_streaming);
 
 	/* determine the toplevel transaction */
-	toptxn = (txn->toptxn) ? txn->toptxn : txn;
+	toptxn = rbtxn_get_toptxn(txn);
 
 	Assert(rbtxn_is_streamed(toptxn));
 
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index 215d149..08dc9ee 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -249,6 +249,24 @@ typedef struct ReorderBufferChange
 	((txn)->txn_flags & RBTXN_SKIPPED_PREPARE) != 0 \
 )
 
+/* Is this a top-level transaction? */
+#define rbtxn_is_toptxn(txn)\
+(\
+	(txn)->toptxn == NULL\
+)
+
+/* Is this a subtransaction? */
+#define rbtxn_is_subtxn(txn)\
+(\
+	(txn)->toptxn != NULL\
+)
+
+/* Get the top-level transaction of this (sub)transaction. */
+#define rbtxn_get_toptxn(txn)\
+(\
+	rbtxn_is_subtxn(txn) ? (txn)->toptxn : (txn)\
+)
+
 typedef struct ReorderBufferTXN
 {
 	/* See above */
-- 
1.8.3.1



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  Cc: [email protected], [email protected], [email protected], [email protected]
  Subject: Re: Add macros for ReorderBufferTXN toptxn
  In-Reply-To: <CAHut+PtrD4xU4OPUB64ZK+DPDhfKn3zph=nDpEWUFFzUvMKo2w@mail.gmail.com>

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