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Consolidate the function pointer types used by dshash.c.

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Commit 8c0d7bafad36434cb08ac2c78e69ae72c194ca20 introduced dshash with hash
and compare functions like DynaHash's, and also variants that take a user
data pointer instead of size.  Simplify the interface by merging them into
a single pair of function pointer types that take both size and a user data
pointer.

Since it is anticipated that memcmp and tag_hash behavior will be a common
requirement, provide wrapper functions dshash_memcmp and dshash_memhash that
conform to the new function types.

Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/20170823054644.efuzftxjpfi6wwqs%40alap3.anarazel.de
This commit is contained in:
Andres Freund 2017-08-24 17:01:36 -07:00
parent 4569715bd6
commit d7694fc148
2 changed files with 39 additions and 63 deletions
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65
src/backend/lib/dshash.c
View File

@ -35,6 +35,7 @@
#include "storage/ipc.h"
#include "storage/lwlock.h"
#include "utils/dsa.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
/*
@ -188,9 +189,8 @@ static inline bool equal_keys(dshash_table *hash_table,
/*
* Create a new hash table backed by the given dynamic shared area, with the
* given parameters. The returned object is allocated in backend-local memory
* using the current MemoryContext. If 'arg' is non-null, the arg variants of
* hash and compare functions must be provided in 'params' and 'arg' will be
* passed down to them.
* using the current MemoryContext. 'arg' will be passed through to the
* compare and hash functions.
*/
dshash_table *
dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
@ -198,14 +198,6 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
dshash_table *hash_table;
dsa_pointer control;
/* Sanity checks on the set of supplied functions. */
Assert((params->compare_function != NULL) ^
(params->compare_arg_function != NULL));
Assert((params->hash_function != NULL) ^
(params->hash_arg_function != NULL));
Assert(arg == NULL || (params->compare_arg_function != NULL));
Assert(arg == NULL || (params->hash_arg_function != NULL));
/* Allocate the backend-local object representing the hash table. */
hash_table = palloc(sizeof(dshash_table));
@ -263,9 +255,8 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
/*
* Attach to an existing hash table using a handle. The returned object is
* allocated in backend-local memory using the current MemoryContext. If
* 'arg' is non-null, the arg variants of hash and compare functions must be
* provided in 'params' and 'arg' will be passed down to them.
* allocated in backend-local memory using the current MemoryContext. 'arg'
* will be passed through to the compare and hash functions.
*/
dshash_table *
dshash_attach(dsa_area *area, const dshash_parameters *params,
@ -274,14 +265,6 @@ dshash_attach(dsa_area *area, const dshash_parameters *params,
dshash_table *hash_table;
dsa_pointer control;
/* Sanity checks on the set of supplied functions. */
Assert((params->compare_function != NULL) ^
(params->compare_arg_function != NULL));
Assert((params->hash_function != NULL) ^
(params->hash_arg_function != NULL));
Assert(arg == NULL || (params->compare_arg_function != NULL));
Assert(arg == NULL || (params->hash_arg_function != NULL));
/* Allocate the backend-local object representing the hash table. */
hash_table = palloc(sizeof(dshash_table));
@ -582,6 +565,24 @@ dshash_release_lock(dshash_table *hash_table, void *entry)
LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
}
/*
* A compare function that forwards to memcmp.
*/
int
dshash_memcmp(const void *a, const void *b, size_t size, void *arg)
{
return memcmp(a, b, size);
}
/*
* A hash function that forwards to tag_hash.
*/
dshash_hash
dshash_memhash(const void *v, size_t size, void *arg)
{
return tag_hash(v, size);
}
/*
* Print debugging information about the internal state of the hash table to
* stderr. The caller must hold no partition locks.
@ -874,11 +875,9 @@ delete_item_from_bucket(dshash_table *hash_table,
static inline dshash_hash
hash_key(dshash_table *hash_table, const void *key)
{
if (hash_table->params.hash_arg_function != NULL)
return hash_table->params.hash_arg_function(key, hash_table->arg);
else
return hash_table->params.hash_function(key,
hash_table->params.key_size);
return hash_table->params.hash_function(key,
hash_table->params.key_size,
hash_table->arg);
}
/*
@ -887,13 +886,7 @@ hash_key(dshash_table *hash_table, const void *key)
static inline bool
equal_keys(dshash_table *hash_table, const void *a, const void *b)
{
int r;
if (hash_table->params.compare_arg_function != NULL)
r = hash_table->params.compare_arg_function(a, b, hash_table->arg);
else
r = hash_table->params.compare_function(a, b,
hash_table->params.key_size);
return r == 0;
return hash_table->params.compare_function(a, b,
hash_table->params.key_size,
hash_table->arg) == 0;
}

37
src/include/lib/dshash.h
View File

@ -26,32 +26,13 @@ typedef dsa_pointer dshash_table_handle;
/* The type for hash values. */
typedef uint32 dshash_hash;
/*
* A function used for comparing keys. This version is compatible with
* HashCompareFunction in hsearch.h and memcmp.
*/
typedef int (*dshash_compare_function) (const void *a, const void *b, size_t size);
/* A function type for comparing keys. */
typedef int (*dshash_compare_function) (const void *a, const void *b,
size_t size, void *arg);
/*
* A function type used for comparing keys. This version allows compare
* functions to receive a pointer to arbitrary user data that was given to the
* create or attach function. Similar to qsort_arg_comparator.
*/
typedef int (*dshash_compare_arg_function) (const void *a, const void *b, void *arg);
/*
* A function type for computing hash values for keys. This version is
* compatible with HashValueFunc in hsearch.h and hash functions like
* tag_hash.
*/
typedef dshash_hash (*dshash_hash_function) (const void *v, size_t size);
/*
* A function type for computing hash values for keys. This version allows
* hash functions to receive a pointer to arbitrary user data that was given
* to the create or attach function.
*/
typedef dshash_hash (*dshash_hash_arg_function) (const void *v, void *arg);
/* A function type for computing hash values for keys. */
typedef dshash_hash (*dshash_hash_function) (const void *v, size_t size,
void *arg);
/*
* The set of parameters needed to create or attach to a hash table. The
@ -70,9 +51,7 @@ typedef struct dshash_parameters
size_t key_size; /* Size of the key (initial bytes of entry) */
size_t entry_size; /* Total size of entry */
dshash_compare_function compare_function; /* Compare function */
dshash_compare_arg_function compare_arg_function; /* Arg version */
dshash_hash_function hash_function; /* Hash function */
dshash_hash_arg_function hash_arg_function; /* Arg version */
int tranche_id; /* The tranche ID to use for locks */
} dshash_parameters;
@ -101,6 +80,10 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
extern void dshash_release_lock(dshash_table *hash_table, void *entry);
/* Convenience hash and compare functions wrapping memcmp and tag_hash. */
extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg);
extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg);
/* Debugging support. */
extern void dshash_dump(dshash_table *hash_table);