* cause further writes to grow the database quickly, and
* stale locks can block further operation.
*
- * Fix: Terminate all programs using the database, or make
- * them close it. Next database user will reset the lockfile.
+ * Fix: Check for stale readers periodically, using the
+ * #mdb_reader_check function or the mdb_stat tool. Or just
+ * make all programs using the database close it; the lockfile
+ * is always reset on first open of the environment.
*
* - On BSD systems or others configured with MDB_USE_POSIX_SEM,
* startup can fail due to semaphores owned by another userid.
* ...when several processes can use a database concurrently:
*
* - Avoid aborting a process with an active transaction.
- * The transaction becomes "long-lived" as above until the lockfile
- * is reset, since the process may not remove it from the lockfile.
+ * The transaction becomes "long-lived" as above until a check
+ * for stale readers is performed or the lockfile is reset,
+ * since the process may not remove it from the lockfile.
*
- * - If you do that anyway, close the environment once in a while,
- * so the lockfile can get reset.
+ * - If you do that anyway, do a periodic check for stale readers. Or
+ * close the environment once in a while, so the lockfile can get reset.
*
* - Do not use MDB databases on remote filesystems, even between
* processes on the same host. This breaks flock() on some OSes,
extern "C" {
#endif
+/** Unix permissions for creating files, or dummy definition for Windows */
#ifdef _MSC_VER
typedef int mdb_mode_t;
#else
/** Library minor version */
#define MDB_VERSION_MINOR 9
/** Library patch version */
-#define MDB_VERSION_PATCH 6
+#define MDB_VERSION_PATCH 7
/** Combine args a,b,c into a single integer for easy version comparisons */
#define MDB_VERINT(a,b,c) (((a) << 24) | ((b) << 16) | (c))
#define MDB_APPEND 0x20000
/** Duplicate data is being appended, don't split full pages. */
#define MDB_APPENDDUP 0x40000
-/** Store multiple data items in one call. */
+/** Store multiple data items in one call. Only for #MDB_DUPFIXED. */
#define MDB_MULTIPLE 0x80000
/* @} */
#define MDB_PAGE_FULL (-30786)
/** Database contents grew beyond environment mapsize */
#define MDB_MAP_RESIZED (-30785)
- /** Database flags changed or would change */
+ /** MDB_INCOMPATIBLE: Operation and DB incompatible, or DB flags changed */
#define MDB_INCOMPATIBLE (-30784)
/** Invalid reuse of reader locktable slot */
#define MDB_BAD_RSLOT (-30783)
-#define MDB_LAST_ERRCODE MDB_BAD_RSLOT
+ /** Transaction cannot recover - it must be aborted */
+#define MDB_BAD_TXN (-30782)
+ /** Too big key/data, key is empty, or wrong DUPFIXED size */
+#define MDB_BAD_VALSIZE (-30781)
+#define MDB_LAST_ERRCODE MDB_BAD_VALSIZE
/** @} */
/** @brief Statistics for a database in the environment */
/** @brief Copy an MDB environment to the specified path.
*
* This function may be used to make a backup of an existing environment.
+ * No lockfile is created, since it gets recreated at need.
+ * @note This call can trigger significant file size growth if run in
+ * parallel with write transactions, because it employs a read-only
+ * transaction. See long-lived transactions under @ref caveats_sec.
* @param[in] env An environment handle returned by #mdb_env_create(). It
* must have already been opened successfully.
* @param[in] path The directory in which the copy will reside. This
/** @brief Copy an MDB environment to the specified file descriptor.
*
* This function may be used to make a backup of an existing environment.
+ * No lockfile is created, since it gets recreated at need.
+ * @note This call can trigger significant file size growth if run in
+ * parallel with write transactions, because it employs a read-only
+ * transaction. See long-lived transactions under @ref caveats_sec.
* @param[in] env An environment handle returned by #mdb_env_create(). It
* must have already been opened successfully.
* @param[in] fd The filedescriptor to write the copy to. It must
*/
int mdb_env_set_maxdbs(MDB_env *env, MDB_dbi dbs);
+ /** @brief Get the maximum size of a key for the environment.
+ *
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @return The maximum size of a key. (#MDB_MAXKEYSIZE)
+ */
+int mdb_env_get_maxkeysize(MDB_env *env);
+
/** @brief Create a transaction for use with the environment.
*
* The transaction handle may be discarded using #mdb_txn_abort() or #mdb_txn_commit().
* @param[in] parent If this parameter is non-NULL, the new transaction
* will be a nested transaction, with the transaction indicated by \b parent
* as its parent. Transactions may be nested to any level. A parent
- * transaction may not issue any other operations besides mdb_txn_begin,
- * mdb_txn_abort, or mdb_txn_commit while it has active child transactions.
+ * transaction and its cursors may not issue any other operations than
+ * mdb_txn_commit and mdb_txn_abort while it has active child transactions.
* @param[in] flags Special options for this transaction. This parameter
* must be set to 0 or by bitwise OR'ing together one or more of the
* values described here.
*/
int mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **txn);
+ /** @brief Returns the transaction's #MDB_env
+ *
+ * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+ */
+MDB_env *mdb_txn_env(MDB_txn *txn);
+
/** @brief Commit all the operations of a transaction into the database.
*
* The transaction handle is freed. It and its cursors must not be used
*/
int mdb_stat(MDB_txn *txn, MDB_dbi dbi, MDB_stat *stat);
+ /** @brief Retrieve the DB flags for a database handle.
+ *
+ * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+ * @param[in] dbi A database handle returned by #mdb_dbi_open()
+ * @param[out] flags Address where the flags will be returned.
+ * @return A non-zero error value on failure and 0 on success.
+ */
+int mdb_dbi_flags(MDB_txn *txn, MDB_dbi dbi, unsigned int *flags);
+
/** @brief Close a database handle.
*
* This call is not mutex protected. Handles should only be closed by
*/
void mdb_dbi_close(MDB_env *env, MDB_dbi dbi);
- /** @brief Delete a database and/or free all its pages.
+ /** @brief Empty or delete+close a database.
*
- * If the \b del parameter is 1, the DB handle will be closed
- * and the DB will be deleted.
* @param[in] txn A transaction handle returned by #mdb_txn_begin()
* @param[in] dbi A database handle returned by #mdb_dbi_open()
- * @param[in] del 1 to delete the DB from the environment,
- * 0 to just free its pages.
+ * @param[in] del 0 to empty the DB, 1 to delete it from the
+ * environment and close the DB handle.
* @return A non-zero error value on failure and 0 on success.
*/
int mdb_drop(MDB_txn *txn, MDB_dbi dbi, int del);
* correct order. Loading unsorted keys with this flag will cause
* data corruption.
* <li>#MDB_APPENDDUP - as above, but for sorted dup data.
+ * <li>#MDB_MULTIPLE - store multiple contiguous data elements in a
+ * single request. This flag may only be specified if the database
+ * was opened with #MDB_DUPFIXED. The \b data argument must be an
+ * array of two MDB_vals. The mv_size of the first MDB_val must be
+ * the size of a single data element. The mv_data of the first MDB_val
+ * must point to the beginning of the array of contiguous data elements.
+ * The mv_size of the second MDB_val must be the count of the number
+ * of data elements to store. On return this field will be set to
+ * the count of the number of elements actually written. The mv_data
+ * of the second MDB_val is unused.
* </ul>
* @return A non-zero error value on failure and 0 on success. Some possible
* errors are:
* @return < 0 if a < b, 0 if a == b, > 0 if a > b
*/
int mdb_dcmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b);
+
+ /** @brief A callback function used to print a message from the library.
+ *
+ * @param[in] msg The string to be printed.
+ * @param[in] ctx An arbitrary context pointer for the callback.
+ * @return < 0 on failure, 0 on success.
+ */
+typedef int (MDB_msg_func)(const char *msg, void *ctx);
+
+ /** @brief Dump the entries in the reader lock table.
+ *
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @param[in] func A #MDB_msg_func function
+ * @param[in] ctx Anything the message function needs
+ * @return < 0 on failure, 0 on success.
+ */
+int mdb_reader_list(MDB_env *env, MDB_msg_func *func, void *ctx);
+
+ /** @brief Check for stale entries in the reader lock table.
+ *
+ * @param[in] env An environment handle returned by #mdb_env_create()
+ * @param[out] dead Number of stale slots that were cleared
+ * @return 0 on success, non-zero on failure.
+ */
+int mdb_reader_check(MDB_env *env, int *dead);
/** @} */
#ifdef __cplusplus
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