ctdb is a simple & lightweight key-value database, based on "copy-on-write"(Append-only) Compressed Trie.
- Add a new key/value pair to the database.
- Delete an existing key from the database.
- Querying the database by a specific key.
- Traverse the database by a specific prefix.
- Support for transactions.
make iter; ./iter
make simple; ./simple
make trans; rm ./test.db; ./trans
make vacuum; rm ./*.db; ./vacuum
put & del:
struct ctdb *db = ctdb_open("./test.db");
struct ctdb_transaction *trans = ctdb_transaction_begin(db);
ctdb_put(trans, "apple", 5, "apple_value", 11);
ctdb_put(trans, "app", 3, "app_value", 9);
ctdb_put(trans, "application", 11, "application_value", 17);
ctdb_del(trans, "app", 3);
ctdb_transaction_commit(trans);
//ctdb_transaction_rollback(trans);
ctdb_transaction_free(trans);
ctdb_close(db);get:
struct ctdb *db = ctdb_open("./test.db");
struct ctdb_transaction *trans = ctdb_transaction_begin(db);
struct ctdb_leaf leaf = ctdb_get(trans, "app", 3);
//seek(db->fd, leaf.value_pos, SEEK_SET)
//read(db->fd, buffer, leaf.value_len)) or sendfile(client_fd, db->fd, &off, leaf.value_len)
ctdb_transaction_free(trans);
ctdb_close(db);traverse:
struct ctdb *db = ctdb_open("./test.db");
struct ctdb_transaction *trans = ctdb_transaction_begin(db);
//traversing data starting with "app"
int res = CTDB_FOREACH(trans, "app", 3,
(int fd, char *key, uint8_t key_len, struct ctdb_leaf leaf){
printf("key:%.*s value_len:%u\n", key_len, key, leaf.value_len);
//return CTDB_ERR; //stop traversal
return CTDB_OK; //continue
}
);
ctdb_transaction_free(trans);
ctdb_close(db);vacuum:
struct ctdb *db = ctdb_open("./test.db");
struct ctdb_transaction *trans = ctdb_transaction_begin(db);
//...
//copy the data to a new file and compress it
struct ctdb *new_db = ctdb_open("./test_tmp.db");
assert(CTDB_OK == ctdb_vacuum(trans, new_db));
ctdb_transaction_free(&trans);
ctdb_close(&new_db);
ctdb_close(&db);