Repurpose PROC_COPYABLE_FLAGS as PROC_XMIN_FLAGS

alvherre · alvherre · commit 8d061acd12af · 2022-05-19T16:20:32.000+02:00
This is a slight, convenient semantics change from what commit 0f0cfb4 ("Fix parallel operations that prevent oldest xmin from advancing") introduced that lets us simplify the coding in the one place where it is used. Backpatch to 13. This is related to commit 6fea655 ("Tighten ComputeXidHorizons' handling of walsenders") rewriting the code site where this is used, which has not yet been backpatched, but it may well be in the future. Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com> Discussion: https://postgr.es/m/202204191637.eldwa2exvguw@alvherre.pgsql
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
@@ -2685,17 +2685,14 @@ 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;
-
-		/* walsender cheats by passing proc == MyProc, don't check its flags */
-		if (proc != MyProc)
-		{
-			/* Flags being copied must be valid copy-able flags. */
-			Assert((proc->statusFlags & (~PROC_COPYABLE_FLAGS)) == 0);
-			MyProc->statusFlags = proc->statusFlags;
-			ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->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
@@ -69,11 +69,10 @@ 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,
