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 eba572b0d8afaff71815b3d9bebdc8ce07f69086..1315762ecf970c257ef35f0787c5a0f1d7bdf039 100644 (file)
--- a/src/backend/access/gin/ginvacuum.c
+++ b/src/backend/access/gin/ginvacuum.c
@@ -710,7 +710,7 @@ 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);