set-gin-metapage-pd_lower-v1.patch

diff --git a/src/backend/access/gin/ginutil.c b/src/backend/access/gin/ginutil.c
index d03d59da6a..b1755c6f1c 100644
--- a/src/backend/access/gin/ginutil.c
+++ b/src/backend/access/gin/ginutil.c
@@ -372,6 +372,13 @@ GinInitMetabuffer(Buffer b)
 	metadata->nDataPages = 0;
 	metadata->nEntries = 0;
 	metadata->ginVersion = GIN_CURRENT_VERSION;
+
+	/*
+	 * Set pd_lower just past the end of the metadata.  This is not essential
+	 * but it makes the page look compressible to xlog.c.
+	 */
+	((PageHeader) page)->pd_lower =
+			((char *) metadata + sizeof(GinMetaPageData)) - (char *) page;
 }
 
 /*
diff --git a/src/backend/access/gin/ginxlog.c b/src/backend/access/gin/ginxlog.c
index 7ba04e324f..95b842bef0 100644
--- a/src/backend/access/gin/ginxlog.c
+++ b/src/backend/access/gin/ginxlog.c
@@ -776,18 +776,11 @@ gin_mask(char *pagedata, BlockNumber blkno)
 	mask_page_hint_bits(page);
 
 	/*
-	 * GIN metapage doesn't use pd_lower/pd_upper. Other page types do. Hence,
-	 * we need to apply masking for those pages.
+	 * For GIN_DELETED page, the page is initialized to empty. Hence, mask
+	 * the page content.
 	 */
-	if (opaque->flags != GIN_META)
-	{
-		/*
-		 * For GIN_DELETED page, the page is initialized to empty. Hence, mask
-		 * the page content.
-		 */
-		if (opaque->flags & GIN_DELETED)
-			mask_page_content(page);
-		else
-			mask_unused_space(page);
-	}
+	if (opaque->flags & GIN_DELETED)
+		mask_page_content(page);
+	else
+		mask_unused_space(page);
 }