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 8dbffbf55f1ffd35c3e8a358c2a53ca6fbb0f22f..31bb27172ba1c7dcbd8806ed9f5ff5ff068bb007 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))
                {
                        RecordFreeIndexPage(index, blkno);
                        totFreePages++;