From: Andres Freund <andres@anarazel.de>
Date: Wed, 24 Jan 2018 07:20:02 +0000 (-0800)
Subject: WIP: Faster order.
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=7648b52925d54f88e55d7969ed1f50be1cc3ea0d;p=users%2Fandresfreund%2Fpostgres.git

WIP: Faster order.

This breaks regression tests, but yields quite impressive speedups.
---

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index c08ab14c02..af4275461b 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -421,9 +421,16 @@ heapgetpage(HeapScanDesc scan, BlockNumber page)
 	 */
 	all_visible = PageIsAllVisible(dp) && !snapshot->takenDuringRecovery;
 
+//#define FASTORDER
+#ifdef FASTORDER
+	for (lineoff = lines, lpp = PageGetItemId(dp, lineoff);
+		 lineoff >= FirstOffsetNumber;
+		 lineoff--, lpp--)
+#else
 	for (lineoff = FirstOffsetNumber, lpp = PageGetItemId(dp, lineoff);
 		 lineoff <= lines;
 		 lineoff++, lpp++)
+#endif
 	{
 		if (ItemIdIsNormal(lpp))
 		{
@@ -2089,8 +2096,9 @@ heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer,
 		/*
 		 * Shouldn't see a HEAP_ONLY tuple at chain start.
 		 */
-		if (at_chain_start && HeapTupleIsHeapOnly(heapTuple))
-			break;
+		Assert(!(at_chain_start && HeapTupleIsHeapOnly(heapTuple)));
+		//if (at_chain_start && HeapTupleIsHeapOnly(heapTuple))
+		//	break;
 
 		/*
 		 * The xmin should match the previous xmax value, else chain is