From 8f55bcedaa9c109543627e9c785dab0ffb0e5c75 Mon Sep 17 00:00:00 2001
From: Peter Geoghegan <pg@bowt.ie>
Date: Wed, 22 Jan 2020 20:59:57 -0800
Subject: [PATCH v2 3/3] Remove "negative infinity" check from _bt_compare().

---
 src/backend/access/nbtree/nbtsearch.c | 32 ++++++++++++++++++---------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c
index dd56fdaaea..b2a2605c47 100644
--- a/src/backend/access/nbtree/nbtsearch.c
+++ b/src/backend/access/nbtree/nbtsearch.c
@@ -348,6 +348,8 @@ _bt_binsrch(Relation rel,
 				high;
 	int32		result,
 				cmpval;
+	bool		isleaf;
+	OffsetNumber noff;
 
 	page = BufferGetPage(buf);
 	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
@@ -359,6 +361,7 @@ _bt_binsrch(Relation rel,
 
 	low = P_FIRSTDATAKEY(opaque);
 	high = PageGetMaxOffsetNumber(page);
+	isleaf = P_ISLEAF(opaque);
 
 	/*
 	 * If there are no keys on the page, return the first available slot. Note
@@ -386,13 +389,20 @@ _bt_binsrch(Relation rel,
 
 	cmpval = key->nextkey ? 0 : 1;	/* select comparison value */
 
+	if (isleaf)
+		noff = InvalidOffsetNumber;
+	else
+		noff = P_FIRSTDATAKEY(opaque);
 	while (high > low)
 	{
 		OffsetNumber mid = low + ((high - low) / 2);
 
 		/* We have low <= mid < high, so mid points at a real slot */
 
-		result = _bt_compare_inl(rel, key, page, mid);
+		if (mid == noff)
+			result = 1;
+		else
+			result = _bt_compare_inl(rel, key, page, mid);
 
 		if (result >= cmpval)
 			low = mid + 1;
@@ -407,7 +417,7 @@ _bt_binsrch(Relation rel,
 	 * On a leaf page, we always return the first key >= scan key (resp. >
 	 * scan key), which could be the last slot + 1.
 	 */
-	if (P_ISLEAF(opaque))
+	if (isleaf)
 		return low;
 
 	/*
@@ -536,6 +546,16 @@ _bt_compare(Relation rel,
 			Page page,
 			OffsetNumber offnum)
 {
+	BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
+
+	/*
+	 * Force result ">" if target item is first data item on an internal page
+	 * --- see NOTE above.
+	 */
+	if (!P_ISLEAF(opaque) && offnum == P_FIRSTDATAKEY(opaque))
+		return 1;
+
+
 	return _bt_compare_inl(rel, key, page, offnum);
 }
 
@@ -568,7 +588,6 @@ _bt_compare_inl(Relation rel,
 				OffsetNumber offnum)
 {
 	TupleDesc	itupdesc = RelationGetDescr(rel);
-	BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
 	IndexTuple	itup;
 	ItemPointer heapTid;
 	int			ski;
@@ -580,13 +599,6 @@ _bt_compare_inl(Relation rel,
 	Assert(key->keysz <= IndexRelationGetNumberOfKeyAttributes(rel));
 	Assert(key->heapkeyspace || key->scantid == NULL);
 
-	/*
-	 * Force result ">" if target item is first data item on an internal page
-	 * --- see NOTE above.
-	 */
-	if (!P_ISLEAF(opaque) && offnum == P_FIRSTDATAKEY(opaque))
-		return 1;
-
 	itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
 	ntupatts = BTreeTupleGetNAtts(itup, rel);
 
-- 
2.17.1