From 80064e90355a443096d16c7310722008315918a2 Mon Sep 17 00:00:00 2001
From: Blake Smith <blakesmith0@gmail.com>
Date: Tue, 20 Aug 2013 19:08:01 -0500
Subject: [PATCH] Use one index entry for a key/value pair

---
 contrib/hstore/hstore_gin.c | 87 ++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 75 insertions(+), 12 deletions(-)

diff --git a/contrib/hstore/hstore_gin.c b/contrib/hstore/hstore_gin.c
index 2007801..e45a244 100644
--- a/contrib/hstore/hstore_gin.c
+++ b/contrib/hstore/hstore_gin.c
@@ -24,7 +24,6 @@
 PG_FUNCTION_INFO_V1(gin_extract_hstore);
 Datum		gin_extract_hstore(PG_FUNCTION_ARGS);
 
-/* Build an indexable text value */
 static text *
 makeitem(char *str, int len, char flag)
 {
@@ -41,6 +40,73 @@ makeitem(char *str, int len, char flag)
 	return item;
 }
 
+/* Build an indexable text value */
+static text *
+makeCombinedItem(HEntry *hsent, char *ptr, int i) {
+	int keylen;
+	int vallen;
+	int len;
+	int valflag;
+	text	   *item;
+
+	keylen = HS_KEYLEN(hsent, i);
+
+	if (HS_VALISNULL(hsent, i)) {
+		valflag = NULLFLAG;
+		vallen = 0;
+	} else {
+		valflag = VALFLAG;
+		vallen = HS_VALLEN(hsent, i);
+	}
+
+	len = keylen + vallen + 2;
+	item = (text *) palloc(len);
+	SET_VARSIZE(item, len);
+
+	*VARDATA(item) = KEYFLAG;
+
+	memcpy(VARDATA(item) + 1,
+		   HS_KEY(hsent, ptr, i), keylen);
+
+	*(VARDATA(item) + 1 + keylen) = valflag;
+
+	memcpy(VARDATA(item) + 2 + keylen,
+		   HS_VAL(hsent, ptr, i), vallen);
+
+	return item;
+}
+
+static Datum
+gin_extract_hstore_contains(PG_FUNCTION_ARGS)
+{
+	HStore	   *hs = PG_GETARG_HS(0);
+	int32	   *nentries = (int32 *) PG_GETARG_POINTER(1);
+	Datum	   *entries = NULL;
+	HEntry	   *hsent = ARRPTR(hs);
+	char	   *ptr = STRPTR(hs);
+	int			count = HS_COUNT(hs);
+	int			i;
+
+	*nentries = count;
+	if (count)
+		entries = (Datum *) palloc(sizeof(Datum) * count);
+
+	for (i = 0; i < count; ++i)
+	{
+		text       *item;
+
+		item = makeCombinedItem(hsent, ptr, i);
+		entries[i] = PointerGetDatum(item);
+	}
+
+	PG_RETURN_POINTER(entries);
+}
+
+/*
+ * Called during indexing. This produces both the combined key/value
+ * index text for contains queries, as well as the key only query for
+ * key contains queries
+ */
 Datum
 gin_extract_hstore(PG_FUNCTION_ARGS)
 {
@@ -58,18 +124,15 @@ gin_extract_hstore(PG_FUNCTION_ARGS)
 
 	for (i = 0; i < count; ++i)
 	{
-		text	   *item;
+		text       *combined;
+		text       *keyonly;
 
-		item = makeitem(HS_KEY(hsent, ptr, i), HS_KEYLEN(hsent, i),
-						KEYFLAG);
-		entries[2 * i] = PointerGetDatum(item);
+		combined = makeCombinedItem(hsent, ptr, i);
+		keyonly = makeitem(HS_KEY(hsent, ptr, i), HS_KEYLEN(hsent, i),
+						   KEYFLAG);
 
-		if (HS_VALISNULL(hsent, i))
-			item = makeitem(NULL, 0, NULLFLAG);
-		else
-			item = makeitem(HS_VAL(hsent, ptr, i), HS_VALLEN(hsent, i),
-							VALFLAG);
-		entries[2 * i + 1] = PointerGetDatum(item);
+		entries[2 * i] = PointerGetDatum(combined);
+		entries[2 * i + 1] = PointerGetDatum(keyonly);
 	}
 
 	PG_RETURN_POINTER(entries);
@@ -90,7 +153,7 @@ gin_extract_hstore_query(PG_FUNCTION_ARGS)
 	{
 		/* Query is an hstore, so just apply gin_extract_hstore... */
 		entries = (Datum *)
-			DatumGetPointer(DirectFunctionCall2(gin_extract_hstore,
+			DatumGetPointer(DirectFunctionCall2(gin_extract_hstore_contains,
 												PG_GETARG_DATUM(0),
 												PointerGetDatum(nentries)));
 		/* ... except that "contains {}" requires a full index scan */
-- 
1.7.12.4 (Apple Git-37)