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Interface differences between TDB and NTDB.
- ntdb shares 'struct TDB_DATA' with tdb, but TDB defines the TDB_DATA
typedef, whereas ntdb defines NTDB_DATA (ie. both are compatible).
If you include both ntdb.h and tdb.h, #include tdb.h first,
otherwise you'll get a compile error when tdb.h re-defined struct
TDB_DATA.
- ntdb functions return NTDB_SUCCESS (ie 0) on success, and a negative
error on failure, whereas tdb functions returned 0 on success, and
-1 on failure. tdb then used tdb_error() to determine the error;
this is also supported in ntdb to ease backwards compatibility,
though the other form is preferred.
- ntdb's ntdb_fetch() returns an error, tdb's returned the data directly
(or tdb_null, and you were supposed to check tdb_error() to find out why).
- ntdb's ntdb_nextkey() frees the old key's dptr, in tdb you needed to do
this manually.
- tdb's tdb_open/tdb_open_ex took an explicit hash size. ntdb's hash table
resizes as required.
- ntdb uses a linked list of attribute structures to implement logging and
alternate hashes. tdb used tdb_open_ex, which was not extensible.
- ntdb does locking on read-only databases (ie. O_RDONLY passed to ntdb_open).
tdb did not: use the NTDB_NOLOCK flag if you want to suppress locking.
- ntdb's log function is simpler than tdb's log function. The string is
already formatted, and it takes an enum ntdb_log_level not a tdb_debug_level,
and which has only three values: NTDB_LOG_ERROR, NTDB_LOG_USE_ERROR and
NTDB_LOG_WARNING.
- ntdb provides ntdb_deq() for comparing two NTDB_DATA, and ntdb_mkdata() for
creating an NTDB_DATA.
- ntdb's ntdb_name() returns a copy of the name even for NTDB_INTERNAL dbs.
- ntdb does not need tdb_reopen() or tdb_reopen_all(). If you call
fork() after during certain operations the child should close the
tdb, or complete the operations before continuing to use the tdb:
ntdb_transaction_start(): child must ntdb_transaction_cancel()
ntdb_lockall(): child must call ntdb_unlockall()
ntdb_lockall_read(): child must call ntdb_unlockall_read()
ntdb_chainlock(): child must call ntdb_chainunlock()
ntdb_parse() callback: child must return from ntdb_parse()
- ntdb will not open a non-tdb file, even if O_CREAT is specified.
- There is no ntdb_traverse_read. For operating on TDB files, you can
simulate it by ntdb_add_flag(tdb, NTDB_RDONLY); ntdb_traverse();
ntdb_remove_flag(tdb, NTDB_RDONLY). This may be desirable because
traverse on TDB files use a write lock on the entire database
unless it's read-only.
- Failure inside a transaction (such as a lock function failing) does
not implicitly cancel the transaction; you still need to call
ntdb_transaction_cancel().
- There is no NTDB_CLEAR_IF_FIRST flag; it has severe scalability and
API problems. If necessary, you can emulate this by using the open
hook and placing a 1-byte lock at offset 4. If your program forks,
you will need to place this lock again in the child.
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