v20-0003-Convert-some-frontend-hash-functions-to-fasthash.patch

From 97c2996c4e081c5612c06da6c80ae87a1d273090 Mon Sep 17 00:00:00 2001
From: John Naylor <john.naylor@postgresql.org>
Date: Tue, 5 Mar 2024 16:59:39 +0700
Subject: [PATCH v20 3/3] Convert some frontend hash functions to fasthash

Also go one step further and remove duplication of
function definitions by creating a new function,
hash_string(), in a new file hashfn_unstable.c.

It's not clear how many of these are perfomance-
sensitive enough to benefit from removing strlen()
calls, but the simplification is worth it on its
own.

WIP: hash_string_with_len() for dynahash/dshash
---
 src/bin/pg_combinebackup/load_manifest.c  | 16 ++---------
 src/bin/pg_dump/pg_dumpall.c              | 17 ++----------
 src/bin/pg_rewind/filemap.c               | 17 ++----------
 src/bin/pg_verifybackup/pg_verifybackup.c | 16 ++---------
 src/common/Makefile                       |  1 +
 src/common/blkreftable.c                  |  4 +--
 src/common/hashfn_unstable.c              | 34 +++++++++++++++++++++++
 src/common/meson.build                    |  1 +
 src/include/common/hashfn_unstable.h      |  3 ++
 9 files changed, 49 insertions(+), 60 deletions(-)
 create mode 100644 src/common/hashfn_unstable.c

diff --git a/src/bin/pg_combinebackup/load_manifest.c b/src/bin/pg_combinebackup/load_manifest.c
index 7bc10fbe10..d9e7f9e1b4 100644
--- a/src/bin/pg_combinebackup/load_manifest.c
+++ b/src/bin/pg_combinebackup/load_manifest.c
@@ -15,7 +15,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
-#include "common/hashfn.h"
+#include "common/hashfn_unstable.h"
 #include "common/logging.h"
 #include "common/parse_manifest.h"
 #include "load_manifest.h"
@@ -38,12 +38,11 @@
  * Define a hash table which we can use to store information about the files
  * mentioned in the backup manifest.
  */
-static uint32 hash_string_pointer(char *s);
 #define SH_PREFIX		manifest_files
 #define SH_ELEMENT_TYPE	manifest_file
 #define SH_KEY_TYPE		char *
 #define	SH_KEY			pathname
-#define SH_HASH_KEY(tb, key)	hash_string_pointer(key)
+#define SH_HASH_KEY(tb, key)	hash_string(key)
 #define SH_EQUAL(tb, a, b)		(strcmp(a, b) == 0)
 #define	SH_SCOPE		extern
 #define SH_RAW_ALLOCATOR	pg_malloc0
@@ -263,14 +262,3 @@ combinebackup_per_wal_range_cb(JsonManifestParseContext *context,
 		manifest->last_wal_range->next = range;
 	manifest->last_wal_range = range;
 }
-
-/*
- * Helper function for manifest_files hash table.
- */
-static uint32
-hash_string_pointer(char *s)
-{
-	unsigned char *ss = (unsigned char *) s;
-
-	return hash_bytes(ss, strlen(s));
-}
diff --git a/src/bin/pg_dump/pg_dumpall.c b/src/bin/pg_dump/pg_dumpall.c
index 046c0dc3b3..73337f3392 100644
--- a/src/bin/pg_dump/pg_dumpall.c
+++ b/src/bin/pg_dump/pg_dumpall.c
@@ -21,7 +21,7 @@
 #include "catalog/pg_authid_d.h"
 #include "common/connect.h"
 #include "common/file_utils.h"
-#include "common/hashfn.h"
+#include "common/hashfn_unstable.h"
 #include "common/logging.h"
 #include "common/string.h"
 #include "dumputils.h"
@@ -33,8 +33,6 @@
 /* version string we expect back from pg_dump */
 #define PGDUMP_VERSIONSTR "pg_dump (PostgreSQL) " PG_VERSION "\n"
 
-static uint32 hash_string_pointer(char *s);
-
 typedef struct
 {
 	uint32		status;
@@ -46,7 +44,7 @@ typedef struct
 #define SH_ELEMENT_TYPE	RoleNameEntry
 #define SH_KEY_TYPE	char *
 #define SH_KEY		rolename
-#define SH_HASH_KEY(tb, key)	hash_string_pointer(key)
+#define SH_HASH_KEY(tb, key)	hash_string(key)
 #define SH_EQUAL(tb, a, b)		(strcmp(a, b) == 0)
 #define SH_STORE_HASH
 #define SH_GET_HASH(tb, a)		(a)->hashval
@@ -1938,17 +1936,6 @@ dumpTimestamp(const char *msg)
 		fprintf(OPF, "-- %s %s\n\n", msg, buf);
 }
 
-/*
- * Helper function for rolename_hash hash table.
- */
-static uint32
-hash_string_pointer(char *s)
-{
-	unsigned char *ss = (unsigned char *) s;
-
-	return hash_bytes(ss, strlen(s));
-}
-
 /*
  * read_dumpall_filters - retrieve database identifier patterns from file
  *
diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c
index 255ddf2ffa..4458324c9d 100644
--- a/src/bin/pg_rewind/filemap.c
+++ b/src/bin/pg_rewind/filemap.c
@@ -28,7 +28,7 @@
 
 #include "catalog/pg_tablespace_d.h"
 #include "common/file_utils.h"
-#include "common/hashfn.h"
+#include "common/hashfn_unstable.h"
 #include "common/string.h"
 #include "datapagemap.h"
 #include "filemap.h"
@@ -38,12 +38,11 @@
  * Define a hash table which we can use to store information about the files
  * appearing in source and target systems.
  */
-static uint32 hash_string_pointer(const char *s);
 #define SH_PREFIX		filehash
 #define SH_ELEMENT_TYPE	file_entry_t
 #define SH_KEY_TYPE		const char *
 #define	SH_KEY			path
-#define SH_HASH_KEY(tb, key)	hash_string_pointer(key)
+#define SH_HASH_KEY(tb, key)	hash_string(key)
 #define SH_EQUAL(tb, a, b)		(strcmp(a, b) == 0)
 #define	SH_SCOPE		static inline
 #define SH_RAW_ALLOCATOR	pg_malloc0
@@ -821,15 +820,3 @@ decide_file_actions(void)
 
 	return filemap;
 }
-
-
-/*
- * Helper function for filemap hash table.
- */
-static uint32
-hash_string_pointer(const char *s)
-{
-	unsigned char *ss = (unsigned char *) s;
-
-	return hash_bytes(ss, strlen(s));
-}
diff --git a/src/bin/pg_verifybackup/pg_verifybackup.c b/src/bin/pg_verifybackup/pg_verifybackup.c
index 0e9b59f2a8..229c642633 100644
--- a/src/bin/pg_verifybackup/pg_verifybackup.c
+++ b/src/bin/pg_verifybackup/pg_verifybackup.c
@@ -19,7 +19,7 @@
 #include <time.h>
 
 #include "common/controldata_utils.h"
-#include "common/hashfn.h"
+#include "common/hashfn_unstable.h"
 #include "common/logging.h"
 #include "common/parse_manifest.h"
 #include "fe_utils/simple_list.h"
@@ -68,12 +68,11 @@ typedef struct manifest_file
  * Define a hash table which we can use to store information about the files
  * mentioned in the backup manifest.
  */
-static uint32 hash_string_pointer(char *s);
 #define SH_PREFIX		manifest_files
 #define SH_ELEMENT_TYPE	manifest_file
 #define SH_KEY_TYPE		char *
 #define	SH_KEY			pathname
-#define SH_HASH_KEY(tb, key)	hash_string_pointer(key)
+#define SH_HASH_KEY(tb, key)	hash_string(key)
 #define SH_EQUAL(tb, a, b)		(strcmp(a, b) == 0)
 #define	SH_SCOPE		static inline
 #define SH_RAW_ALLOCATOR	pg_malloc0
@@ -986,17 +985,6 @@ should_ignore_relpath(verifier_context *context, char *relpath)
 	return false;
 }
 
-/*
- * Helper function for manifest_files hash table.
- */
-static uint32
-hash_string_pointer(char *s)
-{
-	unsigned char *ss = (unsigned char *) s;
-
-	return hash_bytes(ss, strlen(s));
-}
-
 /*
  * Print a progress report based on the global variables.
  *
diff --git a/src/common/Makefile b/src/common/Makefile
index 3d83299432..43a53e6d9d 100644
--- a/src/common/Makefile
+++ b/src/common/Makefile
@@ -59,6 +59,7 @@ OBJS_COMMON = \
 	file_perm.o \
 	file_utils.o \
 	hashfn.o \
+	hashfn_unstable.o \
 	ip.o \
 	jsonapi.o \
 	keywords.o \
diff --git a/src/common/blkreftable.c b/src/common/blkreftable.c
index bfa6f7ab5d..980f44c9df 100644
--- a/src/common/blkreftable.c
+++ b/src/common/blkreftable.c
@@ -37,7 +37,7 @@
 #endif
 
 #include "common/blkreftable.h"
-#include "common/hashfn.h"
+#include "common/hashfn_unstable.h"
 #include "port/pg_crc32c.h"
 
 /*
@@ -124,7 +124,7 @@ struct BlockRefTableEntry
 #define SH_KEY_TYPE BlockRefTableKey
 #define SH_KEY key
 #define SH_HASH_KEY(tb, key) \
-	hash_bytes((const unsigned char *) &key, sizeof(BlockRefTableKey))
+	fasthash32((const char *) &key, sizeof(BlockRefTableKey), 0)
 #define SH_EQUAL(tb, a, b) (memcmp(&a, &b, sizeof(BlockRefTableKey)) == 0)
 #define SH_SCOPE static inline
 #ifdef FRONTEND
diff --git a/src/common/hashfn_unstable.c b/src/common/hashfn_unstable.c
new file mode 100644
index 0000000000..8a2fbd0c3e
--- /dev/null
+++ b/src/common/hashfn_unstable.c
@@ -0,0 +1,34 @@
+/*-------------------------------------------------------------------------
+ *
+ * hashfn_unstable.c
+ *		Convenience hashing functions based on hashfn_unstable.h.
+ *		As described in that header, they must not be used in indexes
+ *		or other on-disk structures.
+ *
+ *
+ * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/common/hashfn_unstable.c
+ *-------------------------------------------------------------------------
+ */
+#include "c.h"
+
+#include "common/hashfn_unstable.h"
+
+
+uint32
+hash_string(const char *s)
+{
+	fasthash_state hs;
+	size_t		s_len;
+
+	fasthash_init(&hs, 0);
+
+	/* Hash string and save the length for tweaking the final mix. */
+	s_len = fasthash_accum_cstring(&hs, s);
+
+	return fasthash_final32(&hs, s_len);
+}
diff --git a/src/common/meson.build b/src/common/meson.build
index de68e408fa..f5bf755b89 100644
--- a/src/common/meson.build
+++ b/src/common/meson.build
@@ -13,6 +13,7 @@ common_sources = files(
   'file_perm.c',
   'file_utils.c',
   'hashfn.c',
+  'hashfn_unstable.c',
   'ip.c',
   'jsonapi.c',
   'keywords.c',
diff --git a/src/include/common/hashfn_unstable.h b/src/include/common/hashfn_unstable.h
index 8998475ccf..3b1e6bf2b5 100644
--- a/src/include/common/hashfn_unstable.h
+++ b/src/include/common/hashfn_unstable.h
@@ -394,4 +394,7 @@ fasthash32(const char *k, size_t len, uint64 seed)
 	return fasthash_reduce32(fasthash64(k, len, seed));
 }
 
+
+extern uint32 hash_string(const char *s);
+
 #endif							/* HASHFN_UNSTABLE_H */
-- 
2.44.0