From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 19 Feb 2014 22:54:35 +0000 (-0500)
Subject: More hacking.
X-Git-Url: http://git.postgresql.org/gitweb/static/developers.postgresql.org?a=commitdiff_plain;h=7364518dcba965fe32eb032ffa305e2dc7f9b287;p=users%2Frhaas%2Fpostgres.git

More hacking.
---

diff --git a/src/backend/utils/mmgr/freepage.c b/src/backend/utils/mmgr/freepage.c
index cb6c8690f5..2e4dda83fc 100644
--- a/src/backend/utils/mmgr/freepage.c
+++ b/src/backend/utils/mmgr/freepage.c
@@ -90,6 +90,8 @@ static bool FreePageManagerGetInternal(FreePageManager *fpm, Size npages,
 static void FreePageBtreeRecycle(FreePageManager *fpm, Size pageno);
 static void FreePageBtreeRemove(FreePageManager *fpm, FreePageBtree *btp,
 					Size index);
+static void FreePagePushSpanLeader(FreePageManager *fpm, Size first_page,
+					   Size npages);
 static bool FreePageManagerPutInternal(FreePageManager *fpm, Size first_page,
 						   Size npages, bool soft);
 static void FreePageBtreeRemove(FreePageManager *fpm, FreePageBtree *btp,
@@ -365,14 +367,35 @@ FreePageManagerGetInternal(FreePageManager *fpm, Size npages, Size *first_page)
 	if (next != NULL)
 		relptr_copy(next->prev, victim->prev);
 
-	/* Remove span from btree. */
+	/*
+	 * If the span we found is exactly the right size, remove it from the
+	 * btree completely.  Otherwise, adjust the btree entry to reflect the
+	 * still-unallocated portion of the span, and put that portion on the
+	 * appropriate free list.
+	 */
 	FreePageBtreeSearch(fpm, victim_page, &result);
 	Assert(result.page_exact != NULL);
-	FreePageBtreeRemove(fpm, result.page_exact, result.index_exact);
-
-	/* XXX.  But the span we found might have been oversized ... we 
-	 * need to put the rest back! */
+	if (victim->npages == npages)
+		FreePageBtreeRemove(fpm, result.page_exact, result.index_exact);
+	else
+	{
+		FreePageBtreeLeafKey *key;
+
+		/* Adjust btree to reflect remaining pages. */
+		Assert(victim->npages > npages);
+		key = &result.page_exact->u.leaf_key[result.index_exact];
+		Assert(key->npages == victim->npages);
+		key->first_page += npages;
+		key->npages -= npages;
+		if (result.index_exact == 0)
+			FreePageBtreeAdjustAncestorKeys(fpm, result.page_exact);
+
+		/* Put the unallocated pages back on the appropriate free list. */
+		FreePagePushSpanLeader(fpm, victim_page + npages,
+							   victim->npages - npages);
+	}
 
+	/* Return results to caller. */
 	*first_page = fpm_pointer_to_page(base, victim);
 	return true;
 }