>From b82e7a3b936b3950b296514f6ee0542132f11e4a Mon Sep 17 00:00:00 2001
From: Jim Nasby <Jim.Nasby@BlueTreble.com>
Date: Tue, 23 Dec 2014 23:00:20 -0600
Subject: [PATCH] Fugly hack to test out XXHash
 (https://code.google.com/p/xxhash/)

---
 src/backend/storage/buffer/buf_table.c |   5 +-
 src/backend/utils/hash/Makefile        |   2 +-
 src/backend/utils/hash/hashfn.c        |  12 +
 src/backend/utils/hash/xxhash.c        | 928 +++++++++++++++++++++++++++++++++
 src/include/utils/hsearch.h            |   5 +
 src/include/utils/xxhash.h             | 158 ++++++
 6 files changed, 1107 insertions(+), 3 deletions(-)
 create mode 100644 src/backend/utils/hash/xxhash.c
 create mode 100644 src/include/utils/xxhash.h

diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c
index 0750b63..7592bd9 100644
--- a/src/backend/storage/buffer/buf_table.c
+++ b/src/backend/storage/buffer/buf_table.c
@@ -23,7 +23,7 @@
 
 #include "storage/bufmgr.h"
 #include "storage/buf_internals.h"
-
+#include "utils/hsearch.h" /* For XXHash stuff */
 
 /* entry for buffer lookup hashtable */
 typedef struct
@@ -60,11 +60,12 @@ InitBufTable(int size)
 	info.keysize = sizeof(BufferTag);
 	info.entrysize = sizeof(BufferLookupEnt);
 	info.num_partitions = NUM_BUFFER_PARTITIONS;
+	info.hash = PGH32;
 
 	SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table",
 								  size, size,
 								  &info,
-								  HASH_ELEM | HASH_BLOBS | HASH_PARTITION);
+								  HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
 }
 
 /*
diff --git a/src/backend/utils/hash/Makefile b/src/backend/utils/hash/Makefile
index 05d347c..c04f971 100644
--- a/src/backend/utils/hash/Makefile
+++ b/src/backend/utils/hash/Makefile
@@ -12,6 +12,6 @@ subdir = src/backend/utils/hash
 top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
-OBJS = dynahash.o hashfn.o
+OBJS = dynahash.o hashfn.o xxhash.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/hash/hashfn.c b/src/backend/utils/hash/hashfn.c
index adb0bd9..0bdc23b 100644
--- a/src/backend/utils/hash/hashfn.c
+++ b/src/backend/utils/hash/hashfn.c
@@ -22,6 +22,7 @@
 #include "postgres.h"
 
 #include "access/hash.h"
+#include "utils/xxhash.h"
 
 
 /*
@@ -67,6 +68,17 @@ uint32_hash(const void *key, Size keysize)
 }
 
 /*
+ * XXhash hackery
+ */
+// #define PGH32(input, length) ((uint32 *) XXH32_no_seed(input, (size_t) length));
+uint32
+PGH32(const void *key, Size keysize)
+{
+	return (uint32) XXH32_no_seed(key, (size_t) keysize);
+}
+
+
+/*
  * bitmap_hash: hash function for keys that are (pointers to) Bitmapsets
  *
  * Note: don't forget to specify bitmap_match as the match function!
diff --git a/src/include/utils/hsearch.h b/src/include/utils/hsearch.h
index dfdf658..bc531c7 100644
--- a/src/include/utils/hsearch.h
+++ b/src/include/utils/hsearch.h
@@ -157,4 +157,9 @@ extern int	bitmap_match(const void *key1, const void *key2, Size keysize);
 
 #define oid_hash uint32_hash	/* Remove me eventually */
 
+/*
+ * XXHash hackery
+ */
+extern uint32 PGH32(const void *key, Size keysize);
+
 #endif   /* HSEARCH_H */
-- 
2.1.2