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Diffstat (limited to 'src/include/lib/dshash.h')
| -rw-r--r-- | src/include/lib/dshash.h | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/src/include/lib/dshash.h b/src/include/lib/dshash.h new file mode 100644 index 0000000..28f8db2 --- /dev/null +++ b/src/include/lib/dshash.h @@ -0,0 +1,112 @@ +/*------------------------------------------------------------------------- + * + * dshash.h + * Concurrent hash tables backed by dynamic shared memory areas. + * + * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * IDENTIFICATION + * src/include/lib/dshash.h + * + *------------------------------------------------------------------------- + */ +#ifndef DSHASH_H +#define DSHASH_H + +#include "utils/dsa.h" + +/* The opaque type representing a hash table. */ +struct dshash_table; +typedef struct dshash_table dshash_table; + +/* A handle for a dshash_table which can be shared with other processes. */ +typedef dsa_pointer dshash_table_handle; + +/* The type for hash values. */ +typedef uint32 dshash_hash; + +/* 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 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 + * members tranche_id and tranche_name do not need to be initialized when + * attaching to an existing hash table. + * + * Compare and hash functions must be supplied even when attaching, because we + * can't safely share function pointers between backends in general. Either + * the arg variants or the non-arg variants should be supplied; the other + * function pointers should be NULL. If the arg variants are supplied then the + * user data pointer supplied to the create and attach functions will be + * passed to the hash and compare functions. + */ +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_hash_function hash_function; /* Hash function */ + int tranche_id; /* The tranche ID to use for locks */ +} dshash_parameters; + +/* Forward declaration of private types for use only by dshash.c. */ +struct dshash_table_item; +typedef struct dshash_table_item dshash_table_item; + +/* + * Sequential scan state. The detail is exposed to let users know the storage + * size but it should be considered as an opaque type by callers. + */ +typedef struct dshash_seq_status +{ + dshash_table *hash_table; /* dshash table working on */ + int curbucket; /* bucket number we are at */ + int nbuckets; /* total number of buckets in the dshash */ + dshash_table_item *curitem; /* item we are currently at */ + dsa_pointer pnextitem; /* dsa-pointer to the next item */ + int curpartition; /* partition number we are at */ + bool exclusive; /* locking mode */ +} dshash_seq_status; + +/* Creating, sharing and destroying from hash tables. */ +extern dshash_table *dshash_create(dsa_area *area, + const dshash_parameters *params, + void *arg); +extern dshash_table *dshash_attach(dsa_area *area, + const dshash_parameters *params, + dshash_table_handle handle, + void *arg); +extern void dshash_detach(dshash_table *hash_table); +extern dshash_table_handle dshash_get_hash_table_handle(dshash_table *hash_table); +extern void dshash_destroy(dshash_table *hash_table); + +/* Finding, creating, deleting entries. */ +extern void *dshash_find(dshash_table *hash_table, + const void *key, bool exclusive); +extern void *dshash_find_or_insert(dshash_table *hash_table, + const void *key, bool *found); +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); + +/* seq scan support */ +extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, + bool exclusive); +extern void *dshash_seq_next(dshash_seq_status *status); +extern void dshash_seq_term(dshash_seq_status *status); +extern void dshash_delete_current(dshash_seq_status *status); + +/* 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); + +#endif /* DSHASH_H */ |