* BSD systems or when otherwise configured with MDB_USE_POSIX_SEM.
* Multiple users can cause startup to fail later, as noted above.
*
+ * - There is normally no pure read-only mode, since readers need write
+ * access to locks and lock file. Exceptions: On read-only filesystems
+ * or with the #MDB_NOLOCK flag described under #mdb_env_open().
+ *
+ * - By default, in versions before 0.9.10, unused portions of the data
+ * file might receive garbage data from memory freed by other code.
+ * (This does not happen when using the #MDB_WRITEMAP flag.) As of
+ * 0.9.10 the default behavior is to initialize such memory before
+ * writing to the data file. Since there may be a slight performance
+ * cost due to this initialization, applications may disable it using
+ * the #MDB_NOMEMINIT flag. Applications handling sensitive data
+ * which must not be written should not use this flag. This flag is
+ * irrelevant when using #MDB_WRITEMAP.
+ *
* - A thread can only use one transaction at a time, plus any child
* transactions. Each transaction belongs to one thread. See below.
* The #MDB_NOTLS flag changes this for read-only transactions.
/** Library minor version */
#define MDB_VERSION_MINOR 9
/** Library patch version */
-#define MDB_VERSION_PATCH 8
+#define MDB_VERSION_PATCH 10
/** Combine args a,b,c into a single integer for easy version comparisons */
#define MDB_VERINT(a,b,c) (((a) << 24) | ((b) << 16) | (c))
MDB_VERINT(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH)
/** The release date of this library version */
-#define MDB_VERSION_DATE "September 9, 2013"
+#define MDB_VERSION_DATE "November 11, 2013"
/** A stringifier for the version info */
#define MDB_VERSTR(a,b,c,d) "MDB " #a "." #b "." #c ": (" d ")"
#define MDB_NOTLS 0x200000
/** don't do any locking, caller must manage their own locks */
#define MDB_NOLOCK 0x400000
+ /** don't do readahead (no effect on Windows) */
+#define MDB_NORDAHEAD 0x800000
+ /** don't initialize malloc'd memory before writing to datafile */
+#define MDB_NOMEMINIT 0x1000000
/** @} */
/** @defgroup mdb_dbi_open Database Flags
* like wild pointer writes and other bad updates into the database.
* Incompatible with nested transactions.
* Processes with and without MDB_WRITEMAP on the same environment do
- * not cooperate well.
+ * not cooperate well.
* <li>#MDB_NOMETASYNC
* Flush system buffers to disk only once per transaction, omit the
* metadata flush. Defer that until the system flushes files to disk,
* that no readers are using old transactions while a writer is
* active. The simplest approach is to use an exclusive lock so that
* no readers may be active at all when a writer begins.
+ * <li>#MDB_NORDAHEAD
+ * Turn off readahead. Most operating systems perform readahead on
+ * read requests by default. This option turns it off if the OS
+ * supports it. Turning it off may help random read performance
+ * when the DB is larger than RAM and system RAM is full.
+ * The option is not implemented on Windows.
+ * <li>#MDB_NOMEMINIT
+ * Don't initialize malloc'd memory before writing to unused spaces
+ * in the data file. By default, memory for pages written to the data
+ * file is obtained using malloc. While these pages may be reused in
+ * subsequent transactions, freshly malloc'd pages will be initialized
+ * to zeroes before use. This avoids persisting leftover data from other
+ * code (that used the heap and subsequently freed the memory) into the
+ * data file. Note that many other system libraries may allocate
+ * and free memory from the heap for arbitrary uses. E.g., stdio may
+ * use the heap for file I/O buffers. This initialization step has a
+ * modest performance cost so some applications may want to disable
+ * it using this flag. This option can be a problem for applications
+ * which handle sensitive data like passwords, and it makes memory
+ * checkers like Valgrind noisy. This flag is not needed with #MDB_WRITEMAP,
+ * which writes directly to the mmap instead of using malloc for pages. The
+ * initialization is also skipped if #MDB_RESERVE is used; the
+ * caller is expected to overwrite all of the memory that was
+ * reserved in that case.
+ * This flag may be changed at any time using #mdb_env_set_flags().
* </ul>
* @param[in] mode The UNIX permissions to set on created files. This parameter
* is ignored on Windows.
*/
int mdb_env_get_path(MDB_env *env, const char **path);
+ /** @brief Return the filedescriptor for the given environment.
+ *
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @param[out] fd Address of a mdb_filehandle_t to contain the descriptor.
+ * @return A non-zero error value on failure and 0 on success. Some possible
+ * errors are:
+ * <ul>
+ * <li>EINVAL - an invalid parameter was specified.
+ * </ul>
+ */
+int mdb_env_get_fd(MDB_env *env, mdb_filehandle_t *fd);
+
/** @brief Set the size of the memory map to use for this environment.
*
* The size should be a multiple of the OS page size. The default is
* reserved space, which the caller can fill in later - before
* the next update operation or the transaction ends. This saves
* an extra memcpy if the data is being generated later.
+ * MDB does nothing else with this memory, the caller is expected
+ * to modify all of the space requested.
* <li>#MDB_APPEND - append the given key/data pair to the end of the
* database. No key comparisons are performed. This option allows
* fast bulk loading when keys are already known to be in the
projects / openldap / blobdiff