Add more temporary debug logging, in 9.4 branch only.

tglsfdc · tglsfdc · commit eef1a609adfd · 2018-04-17T11:26:37.000-04:00
Last night's results were inconclusive, but after more staring at the code I've thought of some more data to gather. Discussion: https://postgr.es/m/6744.1523833660@sss.pgh.pa.us
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
@@ -773,6 +773,8 @@ DefineIndex(Oid relationId,
 
 	PopActiveSnapshot();
 	PrintSnapMgrStatus("concurrent index build, after PopActiveSnapshot");
+	elog(LOG, "concurrent index build: releasing snap %p with regd_count %d, active_count %d",
+		 snapshot, snapshot->regd_count, snapshot->active_count);
 	UnregisterSnapshot(snapshot);
 	PrintSnapMgrStatus("concurrent index build, after UnregisterSnapshot");
 	InvalidateCatalogSnapshot();
diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
@@ -1411,7 +1411,7 @@ PrintSnapMgrStatus(const char *context)
 	for (active = ActiveSnapshot; active != NULL; active = active->as_next)
 		asdepth++;
 
-	elog(LOG, "%s: %d reg snaps, %d active snaps, cat snap %p, xmin %u",
+	elog(LOG, "%s: %d reg snaps, %d active snaps, first snap %p, cat snap %p, xmin %u",
 		 context, RegisteredSnapshots, asdepth,
-		 CatalogSnapshot, MyPgXact->xmin);
+		 FirstXactSnapshot, CatalogSnapshot, MyPgXact->xmin);
 }

Original file line number	Diff line number	Diff line change
`@@ -1411,7 +1411,7 @@ PrintSnapMgrStatus(const char *context)`
`1411`	`1411`	`for (active = ActiveSnapshot; active != NULL; active = active->as_next)`
`1412`	`1412`	`asdepth++;`
`1413`	`1413`
`1414`		`- elog(LOG, "%s: %d reg snaps, %d active snaps, cat snap %p, xmin %u",`
	`1414`	`+ elog(LOG, "%s: %d reg snaps, %d active snaps, first snap %p, cat snap %p, xmin %u",`
`1415`	`1415`	`context, RegisteredSnapshots, asdepth,`
`1416`		`- CatalogSnapshot, MyPgXact->xmin);`
	`1416`	`+ FirstXactSnapshot, CatalogSnapshot, MyPgXact->xmin);`
`1417`	`1417`	`}`