diff options
Diffstat (limited to 'source4/lib/tdb/docs/README')
| -rw-r--r-- | source4/lib/tdb/docs/README | 238 |
1 files changed, 0 insertions, 238 deletions
diff --git a/source4/lib/tdb/docs/README b/source4/lib/tdb/docs/README deleted file mode 100644 index 63fcf5e049..0000000000 --- a/source4/lib/tdb/docs/README +++ /dev/null @@ -1,238 +0,0 @@ -tdb - a trivial database system -tridge@linuxcare.com December 1999 -================================== - -This is a simple database API. It was inspired by the realisation that -in Samba we have several ad-hoc bits of code that essentially -implement small databases for sharing structures between parts of -Samba. As I was about to add another I realised that a generic -database module was called for to replace all the ad-hoc bits. - -I based the interface on gdbm. I couldn't use gdbm as we need to be -able to have multiple writers to the databases at one time. - -Compilation ------------ - -add HAVE_MMAP=1 to use mmap instead of read/write -add NOLOCK=1 to disable locking code - -Testing -------- - -Compile tdbtest.c and link with gdbm for testing. tdbtest will perform -identical operations via tdb and gdbm then make sure the result is the -same - -Also included is tdbtool, which allows simple database manipulation -on the commandline. - -tdbtest and tdbtool are not built as part of Samba, but are included -for completeness. - -Interface ---------- - -The interface is very similar to gdbm except for the following: - -- different open interface. The tdb_open call is more similar to a - traditional open() -- no tdbm_reorganise() function -- no tdbm_sync() function. No operations are cached in the library anyway -- added a tdb_traverse() function for traversing the whole database -- added transactions support - -A general rule for using tdb is that the caller frees any returned -TDB_DATA structures. Just call free(p.dptr) to free a TDB_DATA -return value called p. This is the same as gdbm. - -here is a full list of tdb functions with brief descriptions. - - ----------------------------------------------------------------------- -TDB_CONTEXT *tdb_open(char *name, int hash_size, int tdb_flags, - int open_flags, mode_t mode) - - open the database, creating it if necessary - - The open_flags and mode are passed straight to the open call on the database - file. A flags value of O_WRONLY is invalid - - The hash size is advisory, use zero for a default value. - - return is NULL on error - - possible tdb_flags are: - TDB_CLEAR_IF_FIRST - clear database if we are the only one with it open - TDB_INTERNAL - don't use a file, instaed store the data in - memory. The filename is ignored in this case. - TDB_NOLOCK - don't do any locking - TDB_NOMMAP - don't use mmap - TDB_NOSYNC - don't synchronise transactions to disk - ----------------------------------------------------------------------- -TDB_CONTEXT *tdb_open_ex(char *name, int hash_size, int tdb_flags, - int open_flags, mode_t mode, - tdb_log_func log_fn, - tdb_hash_func hash_fn) - -This is like tdb_open(), but allows you to pass an initial logging and -hash function. Be careful when passing a hash function - all users of -the database must use the same hash function or you will get data -corruption. - - ----------------------------------------------------------------------- -char *tdb_error(TDB_CONTEXT *tdb); - - return a error string for the last tdb error - ----------------------------------------------------------------------- -int tdb_close(TDB_CONTEXT *tdb); - - close a database - ----------------------------------------------------------------------- -int tdb_update(TDB_CONTEXT *tdb, TDB_DATA key, TDB_DATA dbuf); - - update an entry in place - this only works if the new data size - is <= the old data size and the key exists. - on failure return -1 - ----------------------------------------------------------------------- -TDB_DATA tdb_fetch(TDB_CONTEXT *tdb, TDB_DATA key); - - fetch an entry in the database given a key - if the return value has a null dptr then a error occurred - - caller must free the resulting data - ----------------------------------------------------------------------- -int tdb_exists(TDB_CONTEXT *tdb, TDB_DATA key); - - check if an entry in the database exists - - note that 1 is returned if the key is found and 0 is returned if not found - this doesn't match the conventions in the rest of this module, but is - compatible with gdbm - ----------------------------------------------------------------------- -int tdb_traverse(TDB_CONTEXT *tdb, int (*fn)(TDB_CONTEXT *tdb, - TDB_DATA key, TDB_DATA dbuf, void *state), void *state); - - traverse the entire database - calling fn(tdb, key, data, state) on each - element. - - return -1 on error or the record count traversed - - if fn is NULL then it is not called - - a non-zero return value from fn() indicates that the traversal - should stop. Traversal callbacks may not start transactions. - - WARNING: The data buffer given to the callback fn does NOT meet the - alignment restrictions malloc gives you. - ----------------------------------------------------------------------- -int tdb_traverse_read(TDB_CONTEXT *tdb, int (*fn)(TDB_CONTEXT *tdb, - TDB_DATA key, TDB_DATA dbuf, void *state), void *state); - - traverse the entire database - calling fn(tdb, key, data, state) on - each element, but marking the database read only during the - traversal, so any write operations will fail. This allows tdb to - use read locks, which increases the parallelism possible during the - traversal. - - return -1 on error or the record count traversed - - if fn is NULL then it is not called - - a non-zero return value from fn() indicates that the traversal - should stop. Traversal callbacks may not start transactions. - ----------------------------------------------------------------------- -TDB_DATA tdb_firstkey(TDB_CONTEXT *tdb); - - find the first entry in the database and return its key - - the caller must free the returned data - ----------------------------------------------------------------------- -TDB_DATA tdb_nextkey(TDB_CONTEXT *tdb, TDB_DATA key); - - find the next entry in the database, returning its key - - the caller must free the returned data - ----------------------------------------------------------------------- -int tdb_delete(TDB_CONTEXT *tdb, TDB_DATA key); - - delete an entry in the database given a key - ----------------------------------------------------------------------- -int tdb_store(TDB_CONTEXT *tdb, TDB_DATA key, TDB_DATA dbuf, int flag); - - store an element in the database, replacing any existing element - with the same key - - If flag==TDB_INSERT then don't overwrite an existing entry - If flag==TDB_MODIFY then don't create a new entry - - return 0 on success, -1 on failure - ----------------------------------------------------------------------- -int tdb_writelock(TDB_CONTEXT *tdb); - - lock the database. If we already have it locked then don't do anything - ----------------------------------------------------------------------- -int tdb_writeunlock(TDB_CONTEXT *tdb); - unlock the database - ----------------------------------------------------------------------- -int tdb_lockchain(TDB_CONTEXT *tdb, TDB_DATA key); - - lock one hash chain. This is meant to be used to reduce locking - contention - it cannot guarantee how many records will be locked - ----------------------------------------------------------------------- -int tdb_unlockchain(TDB_CONTEXT *tdb, TDB_DATA key); - - unlock one hash chain - ----------------------------------------------------------------------- -int tdb_transaction_start(TDB_CONTEXT *tdb) - - start a transaction. All operations after the transaction start can - either be committed with tdb_transaction_commit() or cancelled with - tdb_transaction_cancel(). - - If you call tdb_transaction_start() again on the same tdb context - while a transaction is in progress, then the same transaction - buffer is re-used. The number of tdb_transaction_{commit,cancel} - operations must match the number of successful - tdb_transaction_start() calls. - - Note that transactions are by default disk synchronous, and use a - recover area in the database to automatically recover the database - on the next open if the system crashes during a transaction. You - can disable the synchronous transaction recovery setup using the - TDB_NOSYNC flag, which will greatly speed up operations at the risk - of corrupting your database if the system crashes. - - Operations made within a transaction are not visible to other users - of the database until a successful commit. - ----------------------------------------------------------------------- -int tdb_transaction_cancel(TDB_CONTEXT *tdb) - - cancel a current transaction, discarding all write and lock - operations that have been made since the transaction started. - - ----------------------------------------------------------------------- -int tdb_transaction_commit(TDB_CONTEXT *tdb) - - commit a current transaction, updating the database and releasing - the transaction locks. - |