Feedback-ID: ia2694551:Fastmail
Date: Thu, 19 May 2022 12:21:58 +0200
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org,
	Noah Misch <noah@leadboat.com>, Peter Geoghegan <pg@bowt.ie>,
	David Rowley <dgrowleyml@gmail.com>,
	Amit Kapila <amit.kapila16@gmail.com>,
	Masahiko Sawada <sawada.mshk@gmail.com>
Subject: Re: Intermittent buildfarm failures on wrasse
Message-ID: <202205191021.fvy2wgxpxaak@alvherre.pgsql>
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I was looking at backpatching this to pg13.  That made me realize that
commit dc7420c2c927 changed things in 14; and before that commit, the
bitmask that is checked is PROCARRAY_FLAGS_VACUUM, which has a
definition independently from whatever proc.h says.  As far as I can
tell, there's no problem with the patches I post here (the backpatched
version for pg13 and p14).  But's it's something to be aware of; and if
we do want to add the additional bits to the bitmask, we should do that
in a separate master-only commit.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/

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	filename="v13-0001-Repurpose-PROC_COPYABLE_FLAGS-as-PROC_XMIN_FLAGS.patch"

From 6595af9af208de33ab431b502e2f178f7d0f8007 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Sat, 14 May 2022 16:51:23 +0200
Subject: [PATCH] Repurpose PROC_COPYABLE_FLAGS as PROC_XMIN_FLAGS

This is a slight, convenient semantics change from what commit
0f0cfb494004 introduced that lets us simplify the coding in the one
place where it is used.
---
 src/backend/storage/ipc/procarray.c | 11 ++++++-----
 src/include/storage/proc.h          |  7 +++----
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 6ff8d8699b..447b6e3de7 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -1916,12 +1916,13 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc)
 		TransactionIdIsNormal(xid) &&
 		TransactionIdPrecedesOrEquals(xid, xmin))
 	{
-		/* Install xmin */
+		/*
+		 * Install xmin and propagate the vacuumFlags that affect how the
+		 * value is interpreted by vacuum.
+		 */
 		MyPgXact->xmin = TransactionXmin = xmin;
-
-		/* Flags being copied must be valid copy-able flags. */
-		Assert((pgxact->vacuumFlags & (~PROC_COPYABLE_FLAGS)) == 0);
-		MyPgXact->vacuumFlags = pgxact->vacuumFlags;
+		MyPgXact->vacuumFlags = (MyPgXact->vacuumFlags & ~PROC_XMIN_FLAGS) |
+			(pgxact->vacuumFlags & PROC_XMIN_FLAGS);
 
 		result = true;
 	}
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 9cf9684b41..7c85b5645b 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -63,11 +63,10 @@ struct XidCache
 	(PROC_IN_VACUUM | PROC_IN_ANALYZE | PROC_VACUUM_FOR_WRAPAROUND)
 
 /*
- * Flags that are valid to copy from another proc, the parallel leader
- * process in practice.  Currently, a flag that is set during parallel
- * vacuum is allowed.
+ * Xmin-related flags. Make sure any flags that affect how the process' Xmin
+ * value is interpreted by VACUUM are included here.
  */
-#define		PROC_COPYABLE_FLAGS (PROC_IN_VACUUM)
+#define		PROC_XMIN_FLAGS (PROC_IN_VACUUM)
 
 /*
  * We allow a small number of "weak" relation locks (AccessShareLock,
-- 
2.30.2


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	filename="v14-0001-Repurpose-PROC_COPYABLE_FLAGS-as-PROC_XMIN_FLAGS.patch"

From 35197d187fe3e7c9e4bd563396c9c7459e39a7ff Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Sat, 14 May 2022 16:51:23 +0200
Subject: [PATCH] Repurpose PROC_COPYABLE_FLAGS as PROC_XMIN_FLAGS

This is a slight, convenient semantics change from what commit
0f0cfb494004 introduced that lets us simplify the coding in the one
place where it is used.
---
 src/backend/storage/ipc/procarray.c | 11 ++++++-----
 src/include/storage/proc.h          |  7 +++----
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 127be9c017..08053a7e8f 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -2686,12 +2686,13 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc)
 		TransactionIdIsNormal(xid) &&
 		TransactionIdPrecedesOrEquals(xid, xmin))
 	{
-		/* Install xmin */
+		/*
+		 * Install xmin and propagate the statusFlags that affect how the
+		 * value is interpreted by vacuum.
+		 */
 		MyProc->xmin = TransactionXmin = xmin;
-
-		/* Flags being copied must be valid copy-able flags. */
-		Assert((proc->statusFlags & (~PROC_COPYABLE_FLAGS)) == 0);
-		MyProc->statusFlags = proc->statusFlags;
+		MyProc->statusFlags = (MyProc->statusFlags & ~PROC_XMIN_FLAGS) |
+			(proc->statusFlags & PROC_XMIN_FLAGS);
 		ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
 
 		result = true;
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 11b514c9ae..1464fad9b9 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -66,11 +66,10 @@ struct XidCache
 	(PROC_IN_VACUUM | PROC_IN_SAFE_IC | PROC_VACUUM_FOR_WRAPAROUND)
 
 /*
- * Flags that are valid to copy from another proc, the parallel leader
- * process in practice.  Currently, flags that are set during parallel
- * vacuum and parallel index creation are allowed.
+ * Xmin-related flags. Make sure any flags that affect how the process' Xmin
+ * value is interpreted by VACUUM are included here.
  */
-#define		PROC_COPYABLE_FLAGS (PROC_IN_VACUUM | PROC_IN_SAFE_IC)
+#define		PROC_XMIN_FLAGS (PROC_IN_VACUUM | PROC_IN_SAFE_IC)
 
 /*
  * We allow a small number of "weak" relation locks (AccessShareLock,
-- 
2.30.2


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