Reuse all-zero pages in GIN.

hlinnaka · hlinnaka · commit 746e7f1c187b · 2015-07-27T12:32:08.000+03:00
In GIN, an all-zeros page would be leaked forever, and never reused. Just
add them to the FSM in vacuum, and they will be reinitialized when grabbed
from the FSM. On master and 9.5, attempting to access the page's opaque
struct also caused an assertion failure, although that was otherwise
harmless.

Reported by Jeff Janes. Backpatch to all supported versions.
diff --git a/src/backend/access/gin/ginvacuum.c b/src/backend/access/gin/ginvacuum.c
@@ -777,7 +777,7 @@ ginvacuumcleanup(PG_FUNCTION_ARGS)
 		LockBuffer(buffer, GIN_SHARE);
 		page = (Page) BufferGetPage(buffer);
 
-		if (GinPageIsDeleted(page))
+		if (PageIsNew(page) || GinPageIsDeleted(page))
 		{
 			Assert(blkno != GIN_ROOT_BLKNO);
 			RecordFreeIndexPage(index, blkno);

Original file line number	Diff line number	Diff line change
`@@ -777,7 +777,7 @@ ginvacuumcleanup(PG_FUNCTION_ARGS)`
`777`	`777`	`LockBuffer(buffer, GIN_SHARE);`
`778`	`778`	`page = (Page) BufferGetPage(buffer);`
`779`	`779`
`780`		`- if (GinPageIsDeleted(page))`
	`780`	`+ if (PageIsNew(page) \|\| GinPageIsDeleted(page))`
`781`	`781`	`{`
`782`	`782`	`Assert(blkno != GIN_ROOT_BLKNO);`
`783`	`783`	`RecordFreeIndexPage(index, blkno);`