Reuse all-zero pages in GIN.

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
index 3308bb2e6298ee996f81c3f34309f547c629e526..98535833d2eaca149e3241d16cad741a3ccecd57 100644 (file)
--- a/src/backend/access/gin/ginvacuum.c
+++ b/src/backend/access/gin/ginvacuum.c
@@ -762,7 +762,7 @@ 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);