* @{
*/
/** @defgroup compat Windows Compatibility Macros
+ * A bunch of macros to minimize the amount of platform-specific ifdefs
+ * needed throughout the rest of the code. When the features this library
+ * needs are similar enough to POSIX to be hidden in a one-or-two line
+ * replacement, this macro approach is used.
* @{
*/
#ifdef _WIN32
#define close(fd) CloseHandle(fd)
#define munmap(ptr,len) UnmapViewOfFile(ptr)
#else
+ /** Lock the reader mutex.
+ */
#define LOCK_MUTEX_R(env) pthread_mutex_lock(&env->me_txns->mti_mutex)
+ /** Unlock the reader mutex.
+ */
#define UNLOCK_MUTEX_R(env) pthread_mutex_unlock(&env->me_txns->mti_mutex)
+
+ /** Lock the writer mutex.
+ * Only a single write transaction is allowed at a time. Other writers
+ * will block waiting for this mutex.
+ */
#define LOCK_MUTEX_W(env) pthread_mutex_lock(&env->me_txns->mti_wmutex)
+ /** Unlock the writer mutex.
+ */
#define UNLOCK_MUTEX_W(env) pthread_mutex_unlock(&env->me_txns->mti_wmutex)
+
+ /** Get the error code for the last failed system function.
+ */
#define ErrCode() errno
+
+ /** An abstraction for a file handle.
+ * On POSIX systems file handles are small integers. On Windows
+ * they're opaque pointers.
+ */
#define HANDLE int
+
+ /** A value for an invalid file handle.
+ * Mainly used to initialize file variables and signify that they are
+ * unused.
+ */
#define INVALID_HANDLE_VALUE -1
+
+ /** Get the size of a memory page for the system.
+ * This is the basic size that the platform's memory manager uses, and is
+ * fundamental to the use of memory-mapped files.
+ */
#define GetPageSize(x) (x) = sysconf(_SC_PAGE_SIZE)
#endif
/** @} */
#ifndef _WIN32
-/* Note: If O_DSYNC is undefined but exists in /usr/include,
+/** A flag for opening a file and requesting synchronous data writes.
+ * This is only used when writing a meta page. It's not strictly needed;
+ * we could just do a normal write and then immediately perform a flush.
+ * But if this flag is available it saves us an extra system call.
+ *
+ * @note If O_DSYNC is undefined but exists in /usr/include,
* preferably set some compiler flag to get the definition.
* Otherwise compile with the less efficient -DMDB_DSYNC=O_SYNC.
*/
#endif
#endif
+ /** A page number in the database.
+ * Note that 64 bit page numbers are overkill, since pages themselves
+ * already represent 12-13 bits of addressable memory, and the OS will
+ * always limit applications to a maximum of 63 bits of address space.
+ *
+ * @note In the #MDB_node structure, we only store 48 bits of this value,
+ * which thus limits us to only 60 bits of addressable data.
+ */
typedef ULONG pgno_t;
+/** @defgroup debug Debug Macros
+ * @{
+ */
#ifndef DEBUG
+ /** Enable debug output.
+ * Set this to 1 for copious tracing. Set to 2 to add dumps of all IDLs
+ * read from and written to the database (used for free space management).
+ */
#define DEBUG 0
#endif
#if !(__STDC_VERSION__ >= 199901L || defined(__GNUC__))
# define DPRINTF (void) /* Vararg macros may be unsupported */
#elif DEBUG
-# define DPRINTF(fmt, ...) /* Requires 2 or more args */ \
+ /** Print a debug message with printf formatting. */
+# define DPRINTF(fmt, ...) /**< Requires 2 or more args */ \
fprintf(stderr, "%s:%d:(%p) " fmt "\n", __func__, __LINE__, pthread_self(), __VA_ARGS__)
#else
# define DPRINTF(fmt, ...) ((void) 0)
#endif
+ /** Print a debug string.
+ * The string is printed literally, with no format processing.
+ */
#define DPUTS(arg) DPRINTF("%s", arg)
+/** @} */
+ /** A default memory page size.
+ * The actual size is platform-dependent, but we use this for
+ * boot-strapping. We probably should not be using this any more.
+ * The #GetPageSize() macro is used to get the actual size.
+ *
+ * Note that we don't currently support Huge pages. On Linux,
+ * regular data files cannot use Huge pages, and in general
+ * Huge pages aren't actually pageable. We rely on the OS
+ * demand-pager to read our data and page it out when memory
+ * pressure from other processes is high. So until OSs have
+ * actual paging support for Huge pages, they're not viable.
+ */
#define PAGESIZE 4096
+
+ /** The minimum number of keys required in a database page.
+ * Setting this to a larger value will place a smaller bound on the
+ * maximum size of a data item. Data items larger than this size will
+ * be pushed into overflow pages instead of being stored directly in
+ * the B-tree node. This value used to default to 4. With a page size
+ * of 4096 bytes that meant that any item larger than 1024 bytes would
+ * go into an overflow page. That also meant that on average 2-3KB of
+ * each overflow page was wasted space. The value cannot be lower than
+ * 2 because then there would no longer be a tree structure. With this
+ * value, items larger than 2KB will go into overflow pages, and on
+ * average only 1KB will be wasted.
+ */
#define MDB_MINKEYS 2
+
+ /** A stamp that identifies a file as an MDB file.
+ * There's nothing special about this value other than that it is easily
+ * recognizable, and it will reflect any byte order mismatches.
+ */
#define MDB_MAGIC 0xBEEFC0DE
+
+ /** The version number for a database's file format. */
#define MDB_VERSION 1
+
+ /** The maximum size of a key in the database.
+ * While data items have essentially unbounded size, we require that
+ * keys all fit onto a regular page. This limit could be raised a bit
+ * further if needed; to something just under #PAGESIZE / #MDB_MINKEYS.
+ */
#define MAXKEYSIZE 511
+
#if DEBUG
-#define KBUF (MAXKEYSIZE*2+1)
-#define DKBUF char kbuf[KBUF]
+ /** A key buffer.
+ * @ingroup debug
+ * This is used for printing a hex dump of a key's contents.
+ */
+#define DKBUF char kbuf[(MAXKEYSIZE*2+1)]
+ /** Display a key in hex.
+ * @ingroup debug
+ * Invoke a function to display a key in hex.
+ */
#define DKEY(x) mdb_dkey(x, kbuf)
#else
#define DKBUF
#define DKEY(x)
#endif
-/* The DB view is always consistent because all writes are wrapped in
- * the wmutex. Finer-grained locks aren't necessary.
+/** @defgroup lazylock Lazy Locking
+ * Macros for locks that are't actually needed.
+ * The DB view is always consistent because all writes are wrapped in
+ * the wmutex. Finer-grained locks aren't necessary.
+ * @{
*/
#ifndef LAZY_LOCKS
+ /** Use lazy locking. I.e., don't lock these accesses at all. */
#define LAZY_LOCKS 1
#endif
#if LAZY_LOCKS
+ /** Grab the reader lock */
#define LAZY_MUTEX_LOCK(x)
+ /** Release the reader lock */
#define LAZY_MUTEX_UNLOCK(x)
+ /** Release the DB table reader/writer lock */
#define LAZY_RWLOCK_UNLOCK(x)
+ /** Grab the DB table write lock */
#define LAZY_RWLOCK_WRLOCK(x)
+ /** Grab the DB table read lock */
#define LAZY_RWLOCK_RDLOCK(x)
+ /** Declare the DB table rwlock */
#define LAZY_RWLOCK_DEF(x)
+ /** Initialize the DB table rwlock */
#define LAZY_RWLOCK_INIT(x,y)
+ /** Destroy the DB table rwlock */
#define LAZY_RWLOCK_DESTROY(x)
#else
#define LAZY_MUTEX_LOCK(x) pthread_mutex_lock(x)
#define LAZY_RWLOCK_INIT(x,y) pthread_rwlock_init(x,y)
#define LAZY_RWLOCK_DESTROY(x) pthread_rwlock_destroy(x)
#endif
+/** @} */
+ /** An invalid page number.
+ * Mainly used to denote an empty tree.
+ */
#define P_INVALID (~0UL)
+ /** Test if a flag \b f is set in a flag word \b w. */
#define F_ISSET(w, f) (((w) & (f)) == (f))
+ /** Used for offsets within a single page.
+ * Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+ * this is plenty.
+ */
typedef uint16_t indx_t;
-#define DEFAULT_READERS 126
+ /** Default size of memory map.
+ * This is certainly too small for any actual applications. Apps should always set
+ * the size explicitly using #mdb_env_set_mapsize().
+ */
#define DEFAULT_MAPSIZE 1048576
-/* Lock descriptor stuff */
+/** @defgroup readers Reader Lock Table
+ * Readers don't acquire any locks for their data access. Instead, they
+ * simply record their transaction ID in the reader table. The reader
+ * mutex is needed just to find an empty slot in the reader table. The
+ * slot's address is saved in thread-specific data so that subsequent read
+ * transactions started by the same thread need no further locking to proceed.
+ *
+ * Since the database uses multi-version concurrency control, readers don't
+ * actually need any locking. This table is used to keep track of which
+ * readers are using data from which old transactions, so that we'll know
+ * when a particular old transaction is no longer in use, Old transactions
+ * that have freed any data pages can then have their freed pages reclaimed
+ * for use by a later write transaction.
+ *
+ * The lock table is constructed such that reader slots are aligned with the
+ * processor's cache line size. Any slot is only ever used by one thread.
+ * This alignment guarantees that there will be no contention or cache
+ * thrashing as threads update their own slot info, and also eliminates
+ * any need for locking when accessing a slot.
+ *
+ * A writer thread will scan every slot in the table to determine the oldest
+ * outstanding reader transaction. Any freed pages older than this will be
+ * reclaimed by the writer. The writer doesn't use any locks when scanning
+ * this table. This means that there's no guarantee that the writer will
+ * see the most up-to-date reader info, but that's not required for correct
+ * operation - all we need is to know the upper bound on the oldest reader,
+ * we don't care at all about the newest reader. So the only consequence of
+ * reading stale information here is that old pages might hang around a
+ * while longer before being reclaimed. That's actually good anyway, because
+ * the longer we delay reclaiming old pages, the more likely it is that a
+ * string of contiguous pages can be found after coalescing old pages from
+ * many old transactions together.
+ *
+ * @todo We don't actually do such coalescing yet, we grab pages from one
+ * old transaction at a time.
+ * @{
+ */
+ /** Number of slots in the reader table.
+ * This value was chosen somewhat arbitrarily. 126 readers plus a
+ * couple mutexes fit exactly into 8KB on my development machine.
+ * Applications should set the table size using #mdb_env_set_maxreaders().
+ */
+#define DEFAULT_READERS 126
+
+ /** The size of a CPU cache line in bytes. We want our lock structures
+ * aligned to this size to avoid false cache line sharing in the
+ * lock table.
+ * This value works for most CPUs. For Itanium this should be 128.
+ */
#ifndef CACHELINE
-#define CACHELINE 64 /* most CPUs. Itanium uses 128 */
+#define CACHELINE 64
#endif
+ /** The information we store in a single slot of the reader table.
+ * In addition to a transaction ID, we also record the process and
+ * thread ID that owns a slot, so that we can detect stale information,
+ * e.g. threads or processes that went away without cleaning up.
+ * @note We currently don't check for stale records. We simply re-init
+ * the table when we know that we're the only process opening the
+ * lock file.
+ */
typedef struct MDB_rxbody {
+ /** The current Transaction ID when this transaction began.
+ * Multiple readers that start at the same time will probably have the
+ * same ID here. Again, it's not important to exclude them from
+ * anything; all we need to know is which version of the DB they
+ * started from so we can avoid overwriting any data used in that
+ * particular version.
+ */
ULONG mrb_txnid;
+ /** The process ID of the process owning this reader txn. */
pid_t mrb_pid;
+ /** The thread ID of the thread owning this txn. */
pthread_t mrb_tid;
} MDB_rxbody;
+ /** The actual reader record, with cacheline padding. */
typedef struct MDB_reader {
union {
MDB_rxbody mrx;
+ /** shorthand for mrb_txnid */
#define mr_txnid mru.mrx.mrb_txnid
#define mr_pid mru.mrx.mrb_pid
#define mr_tid mru.mrx.mrb_tid
- /* cache line alignment */
+ /** cache line alignment */
char pad[(sizeof(MDB_rxbody)+CACHELINE-1) & ~(CACHELINE-1)];
} mru;
} MDB_reader;
+ /** The header for the reader table.
+ * The table resides in a memory-mapped file. (This is a different file
+ * than is used for the main database.)
+ *
+ * For POSIX the actual mutexes reside in the shared memory of this
+ * mapped file. On Windows, mutexes are named objects allocated by the
+ * kernel; we store the mutex names in this mapped file so that other
+ * processes can grab them. This same approach will also be used on
+ * MacOSX/Darwin (using named semaphores) since MacOSX doesn't support
+ * process-shared POSIX mutexes.
+ */
typedef struct MDB_txbody {
+ /** Stamp identifying this as an MDB lock file. It must be set
+ * to #MDB_MAGIC. */
uint32_t mtb_magic;
+ /** Version number of this lock file. Must be set to #MDB_VERSION. */
uint32_t mtb_version;
-/* For POSIX the actual mutexes reside in shared memory.
- * On Windows, mutexes are allocated by the kernel; we store
- * the name in shared memory so that other processes can
- * grab them.
- */
#ifdef _WIN32
char mtb_rmname[32];
#else
+ /** Mutex protecting access to this table.
+ * This is the reader lock that #LOCK_MUTEX_R acquires.
+ */
pthread_mutex_t mtb_mutex;
#endif
+ /** The ID of the last transaction committed to the database.
+ * This is recorded here only for convenience; the value can always
+ * be determined by reading the main database meta pages.
+ */
ULONG mtb_txnid;
+ /** The number of slots that have been used in the reader table.
+ * This always records the maximum count, it is not decremented
+ * when readers release their slots.
+ */
uint32_t mtb_numreaders;
+ /** The ID of the most recent meta page in the database.
+ * This is recorded here only for convenience; the value can always
+ * be determined by reading the main database meta pages.
+ */
uint32_t mtb_me_toggle;
} MDB_txbody;
+ /** The actual reader table definition. */
typedef struct MDB_txninfo {
union {
MDB_txbody mtb;
} mt2;
MDB_reader mti_readers[1];
} MDB_txninfo;
+/** @} */
-/* Common header for all page types. Overflow pages
- * occupy a number of contiguous pages with no
+/** Common header for all page types.
+ * Overflow pages occupy a number of contiguous pages with no
* headers on any page after the first.
*/
-typedef struct MDB_page { /* represents a page of storage */
-#define mp_pgno mp_p.p_pgno
-#define mp_next mp_p.p_align
- union padded {
- pgno_t p_pgno; /* page number */
- void * p_align; /* for IL32P64 */
- } mp_p;
-#define P_BRANCH 0x01 /* branch page */
-#define P_LEAF 0x02 /* leaf page */
-#define P_OVERFLOW 0x04 /* overflow page */
-#define P_META 0x08 /* meta page */
-#define P_DIRTY 0x10 /* dirty page */
-#define P_LEAF2 0x20 /* DB with small, fixed size keys and no data */
+typedef struct MDB_page {
+ union {
+ pgno_t mp_pgno; /**< page number */
+ void * mp_next; /**< for in-memory list of freed structs */
+ };
+#define P_BRANCH 0x01 /**< branch page */
+#define P_LEAF 0x02 /**< leaf page */
+#define P_OVERFLOW 0x04 /**< overflow page */
+#define P_META 0x08 /**< meta page */
+#define P_DIRTY 0x10 /**< dirty page */
+#define P_LEAF2 0x20 /**< for #MDB_DUPFIXED records */
uint32_t mp_flags;
-#define mp_lower mp_pb.pb.pb_lower
-#define mp_upper mp_pb.pb.pb_upper
-#define mp_pages mp_pb.pb_pages
- union page_bounds {
+ union {
struct {
- indx_t pb_lower; /* lower bound of free space */
- indx_t pb_upper; /* upper bound of free space */
- } pb;
- uint32_t pb_pages; /* number of overflow pages */
- } mp_pb;
- indx_t mp_ptrs[1]; /* dynamic size */
+ indx_t mp_lower; /**< lower bound of free space */
+ indx_t mp_upper; /**< upper bound of free space */
+ };
+ uint32_t mp_pages; /**< number of overflow pages */
+ };
+ indx_t mp_ptrs[1]; /**< dynamic size */
} MDB_page;
+ /** Size of the page header, excluding dynamic data at the end */
#define PAGEHDRSZ ((unsigned) offsetof(MDB_page, mp_ptrs))
+ /** Address of first usable data byte in a page, after the header */
+#define METADATA(p) ((void *)((char *)(p) + PAGEHDRSZ))
+
+ /** Number of nodes on a page */
#define NUMKEYS(p) (((p)->mp_lower - PAGEHDRSZ) >> 1)
+
+ /** The amount of space remaining in the page */
#define SIZELEFT(p) (indx_t)((p)->mp_upper - (p)->mp_lower)
+
+ /** The percentage of space used in the page, in tenths of a percent. */
#define PAGEFILL(env, p) (1000L * ((env)->me_psize - PAGEHDRSZ - SIZELEFT(p)) / \
((env)->me_psize - PAGEHDRSZ))
+ /** The minimum page fill factor, in tenths of a percent.
+ * Pages emptier than this are candidates for merging.
+ */
+#define FILL_THRESHOLD 250
+
+ /** Test if a page is a leaf page */
#define IS_LEAF(p) F_ISSET((p)->mp_flags, P_LEAF)
+ /** Test if a page is a LEAF2 page */
#define IS_LEAF2(p) F_ISSET((p)->mp_flags, P_LEAF2)
+ /** Test if a page is a branch page */
#define IS_BRANCH(p) F_ISSET((p)->mp_flags, P_BRANCH)
+ /** Test if a page is an overflow page */
#define IS_OVERFLOW(p) F_ISSET((p)->mp_flags, P_OVERFLOW)
+ /** The number of overflow pages needed to store the given size. */
#define OVPAGES(size, psize) ((PAGEHDRSZ-1 + (size)) / (psize) + 1)
+ /** Header for a single key/data pair within a page.
+ * We guarantee 2-byte alignment for nodes.
+ */
+typedef struct MDB_node {
+ /** lo and hi are used for data size on leaf nodes and for
+ * child pgno on branch nodes. On 64 bit platforms, flags
+ * is also used for pgno. (branch nodes ignore flags)
+ */
+ unsigned short mn_lo;
+ unsigned short mn_hi; /**< part of dsize or pgno */
+ unsigned short mn_flags; /**< flags for special node types */
+#define F_BIGDATA 0x01 /**< data put on overflow page */
+#define F_SUBDATA 0x02 /**< data is a sub-database */
+#define F_DUPDATA 0x04 /**< data has duplicates */
+ unsigned short mn_ksize; /**< key size */
+ char mn_data[1]; /**< key and data are appended here */
+} MDB_node;
+
+ /** Size of the node header, excluding dynamic data at the end */
+#define NODESIZE offsetof(MDB_node, mn_data)
+
+ /** Size of a node in a branch page.
+ * This is just the node header plus the key, there is no data.
+ */
+#define INDXSIZE(k) (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))
+
+ /** Size of a node in a leaf page.
+ * This is node header plus key plus data size.
+ */
+#define LEAFSIZE(k, d) (NODESIZE + (k)->mv_size + (d)->mv_size)
+
+ /** Address of node \i in page \p */
+#define NODEPTR(p, i) ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i]))
+
+ /** Address of the key for the node */
+#define NODEKEY(node) (void *)((node)->mn_data)
+
+ /** Address of the data for a node */
+#define NODEDATA(node) (void *)((char *)(node)->mn_data + (node)->mn_ksize)
+
+ /** Get the page number pointed to by a branch node */
+#if LONG_MAX == 0x7fffffff
+#define NODEPGNO(node) ((node)->mn_lo | ((node)->mn_hi << 16))
+ /** Set the page number in a branch node */
+#define SETPGNO(node,pgno) do { \
+ (node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16;} while(0)
+#else
+#define NODEPGNO(node) ((node)->mn_lo | ((node)->mn_hi << 16) | ((unsigned long)(node)->mn_flags << 32))
+ /** Set the page number in a branch node */
+#define SETPGNO(node,pgno) do { \
+ (node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
+ (node)->mn_flags = (pgno) >> 32; } while(0)
+#endif
+
+ /** Get the size of the data in a leaf node */
+#define NODEDSZ(node) ((node)->mn_lo | ((unsigned)(node)->mn_hi << 16))
+ /** Set the size of the data for a leaf node */
+#define SETDSZ(node,size) do { \
+ (node)->mn_lo = (size) & 0xffff; (node)->mn_hi = (size) >> 16;} while(0)
+ /** The size of a key in a node */
+#define NODEKSZ(node) ((node)->mn_ksize)
+
+ /** The address of a key in a LEAF2 page.
+ * LEAF2 pages are used for #MDB_DUPFIXED sorted-duplicate sub-DBs.
+ * There are no node headers, keys are stored contiguously.
+ */
+#define LEAF2KEY(p, i, ks) ((char *)(p) + PAGEHDRSZ + ((i)*(ks)))
+
+ /** Set the \b node's key into \b key, if requested. */
+#define MDB_SET_KEY(node, key) if (key!=NULL) {(key)->mv_size = NODEKSZ(node); (key)->mv_data = NODEKEY(node);}
+
+ /** Information about a single database in the environment. */
typedef struct MDB_db {
- uint32_t md_pad; /* also ksize for LEAF2 pages */
- uint16_t md_flags;
- uint16_t md_depth;
- ULONG md_branch_pages;
- ULONG md_leaf_pages;
- ULONG md_overflow_pages;
- ULONG md_entries;
- pgno_t md_root;
+ uint32_t md_pad; /**< also ksize for LEAF2 pages */
+ uint16_t md_flags; /**< @ref mdb_open */
+ uint16_t md_depth; /**< depth of this tree */
+ ULONG md_branch_pages; /**< number of internal pages */
+ ULONG md_leaf_pages; /**< number of leaf pages */
+ ULONG md_overflow_pages; /**< number of overflow pages */
+ ULONG md_entries; /**< number of data items */
+ pgno_t md_root; /**< the root page of this tree */
} MDB_db;
+ /** Handle for the DB used to track free pages. */
#define FREE_DBI 0
+ /** Handle for the default DB. */
#define MAIN_DBI 1
-typedef struct MDB_meta { /* meta (footer) page content */
+ /** Meta page content. */
+typedef struct MDB_meta {
+ /** Stamp identifying this as an MDB data file. It must be set
+ * to #MDB_MAGIC. */
uint32_t mm_magic;
+ /** Version number of this lock file. Must be set to #MDB_VERSION. */
uint32_t mm_version;
- void *mm_address; /* address for fixed mapping */
- size_t mm_mapsize; /* size of mmap region */
- MDB_db mm_dbs[2]; /* first is free space, 2nd is main db */
+ void *mm_address; /**< address for fixed mapping */
+ size_t mm_mapsize; /**< size of mmap region */
+ MDB_db mm_dbs[2]; /**< first is free space, 2nd is main db */
+ /** The size of pages used in this DB */
#define mm_psize mm_dbs[0].md_pad
+ /** Any persistent environment flags. @ref mdb_env */
#define mm_flags mm_dbs[0].md_flags
- pgno_t mm_last_pg; /* last used page in file */
- ULONG mm_txnid; /* txnid that committed this page */
+ pgno_t mm_last_pg; /**< last used page in file */
+ ULONG mm_txnid; /**< txnid that committed this page */
} MDB_meta;
-typedef struct MDB_oldpages {
- struct MDB_oldpages *mo_next;
- ULONG mo_txnid;
- pgno_t mo_pages[1]; /* dynamic */
-} MDB_oldpages;
+ /** Auxiliary DB info.
+ * The information here is mostly static/read-only. There is
+ * only a single copy of this record in the environment.
+ * The \b md_dirty flag is not read-only, but only a write
+ * transaction can ever update it, and only write transactions
+ * need to worry about it.
+ */
+typedef struct MDB_dbx {
+ MDB_val md_name; /**< name of the database */
+ MDB_cmp_func *md_cmp; /**< function for comparing keys */
+ MDB_cmp_func *md_dcmp; /**< function for comparing data items */
+ MDB_rel_func *md_rel; /**< user relocate function */
+ MDB_dbi md_parent; /**< parent DB of a sub-DB */
+ unsigned int md_dirty; /**< TRUE if DB was written in this txn */
+} MDB_dbx;
-static MDB_page *mdb_alloc_page(MDB_cursor *mc, int num);
-static int mdb_touch(MDB_cursor *mc);
+ /** A database transaction.
+ * Every operation requires a transaction handle.
+ */
+struct MDB_txn {
+ pgno_t mt_next_pgno; /**< next unallocated page */
+ /** The ID of this transaction. IDs are integers incrementing from 1.
+ * Only committed write transactions increment the ID. If a transaction
+ * aborts, the ID may be re-used by the next writer.
+ */
+ ULONG mt_txnid;
+ MDB_env *mt_env; /**< the DB environment */
+ /** The list of pages that became unused during this transaction.
+ * This is an #IDL.
+ */
+ pgno_t *mt_free_pgs;
+ union {
+ ID2L dirty_list; /**< modified pages */
+ MDB_reader *reader; /**< this thread's slot in the reader table */
+ } mt_u;
+ /** Array of records for each DB known in the environment. */
+ MDB_dbx *mt_dbxs;
+ /** Array of MDB_db records for each known DB */
+ MDB_db *mt_dbs;
+ /** Number of DB records in use. This number only ever increments;
+ * we don't decrement it when individual DB handles are closed.
+ */
+ unsigned int mt_numdbs;
+
+#define MDB_TXN_RDONLY 0x01 /**< read-only transaction */
+#define MDB_TXN_ERROR 0x02 /**< an error has occurred */
+ unsigned int mt_flags;
+ /** Tracks which of the two meta pages was used at the start
+ * of this transaction.
+ */
+ unsigned int mt_toggle;
+};
-/* Enough space for 2^32 nodes with minimum of 2 keys per node. I.e., plenty.
+/** Enough space for 2^32 nodes with minimum of 2 keys per node. I.e., plenty.
* At 4 keys per node, enough for 2^64 nodes, so there's probably no need to
* raise this on a 64 bit machine.
*/
struct MDB_xcursor;
+ /** Cursors are used for all DB operations */
struct MDB_cursor {
+ /** Context used for databases with #MDB_DUPSORT, otherwise NULL */
struct MDB_xcursor *mc_xcursor;
+ /** The transaction that owns this cursor */
MDB_txn *mc_txn;
+ /** The database handle this cursor operates on */
MDB_dbi mc_dbi;
- unsigned short mc_snum; /* number of pushed pages */
- unsigned short mc_top; /* index of top page, mc_snum-1 */
+ unsigned short mc_snum; /**< number of pushed pages */
+ unsigned short mc_top; /**< index of top page, mc_snum-1 */
unsigned int mc_flags;
-#define C_INITIALIZED 0x01
-#define C_EOF 0x02
-#define C_XDIRTY 0x04
- MDB_page *mc_pg[CURSOR_STACK]; /* stack of pushed pages */
- indx_t mc_ki[CURSOR_STACK]; /* stack of page indices */
+#define C_INITIALIZED 0x01 /**< cursor has been initialized and is valid */
+#define C_EOF 0x02 /**< No more data */
+#define C_XDIRTY 0x04 /**< @deprecated mc_xcursor needs to be flushed */
+ MDB_page *mc_pg[CURSOR_STACK]; /**< stack of pushed pages */
+ indx_t mc_ki[CURSOR_STACK]; /**< stack of page indices */
};
-#define METADATA(p) ((void *)((char *)(p) + PAGEHDRSZ))
-
-/* We guarantee 2-byte alignment for nodes */
-typedef struct MDB_node {
- /* lo and hi are used for data size on leaf nodes and for
- * child pgno on branch nodes. On 64 bit platforms, flags
- * is also used for pgno. (branch nodes ignore flags)
+ /** Context for sorted-dup records.
+ * We could have gone to a fully recursive design, with arbitrarily
+ * deep nesting of sub-databases. But for now we only handle these
+ * levels - main DB, optional sub-DB, sorted-duplicate DB.
*/
- unsigned short mn_lo;
- unsigned short mn_hi;
- unsigned short mn_flags;
-#define F_BIGDATA 0x01 /* data put on overflow page */
-#define F_SUBDATA 0x02 /* data is a sub-database */
-#define F_DUPDATA 0x04 /* data has duplicates */
- unsigned short mn_ksize; /* key size */
- char mn_data[1];
-} MDB_node;
-
-typedef struct MDB_dbx {
- MDB_val md_name;
- MDB_cmp_func *md_cmp; /* user compare function */
- MDB_cmp_func *md_dcmp; /* user dupsort function */
- MDB_rel_func *md_rel; /* user relocate function */
- MDB_dbi md_parent;
- unsigned int md_dirty;
-} MDB_dbx;
-
-struct MDB_txn {
- pgno_t mt_next_pgno; /* next unallocated page */
- ULONG mt_txnid;
- MDB_env *mt_env;
- pgno_t *mt_free_pgs; /* this is an IDL */
- union {
- ID2L dirty_list; /* modified pages */
- MDB_reader *reader;
- } mt_u;
- MDB_dbx *mt_dbxs; /* array */
- MDB_db *mt_dbs;
- unsigned int mt_numdbs;
-
-#define MDB_TXN_RDONLY 0x01 /* read-only transaction */
-#define MDB_TXN_ERROR 0x02 /* an error has occurred */
- unsigned int mt_flags;
- unsigned int mt_toggle;
-};
-
-/* Context for sorted-dup records */
typedef struct MDB_xcursor {
+ /** A sub-cursor for traversing the Dup DB */
MDB_cursor mx_cursor;
+ /** A fake transaction struct for pointing to our own table
+ * of DB info.
+ */
MDB_txn mx_txn;
+ /** Our private DB information tables. Slots 0 and 1 are always
+ * copies of the corresponding slots in the main transaction. These
+ * hold the FREEDB and MAINDB, respectively. If the main cursor is
+ * on a sub-database, that will be copied to slot 2, and the duplicate
+ * database info will be in slot 3. If the main cursor is on the MAINDB
+ * then the duplicate DB info will be in slot 2 and slot 3 will be unused.
+ */
MDB_dbx mx_dbxs[4];
+ /** MDB_db table */
MDB_db mx_dbs[4];
} MDB_xcursor;
+ /** A set of pages freed by an earlier transaction. */
+typedef struct MDB_oldpages {
+ /** Usually we only read one record from the FREEDB at a time, but
+ * in case we read more, this will chain them together.
+ */
+ struct MDB_oldpages *mo_next;
+ /** The ID of the transaction in which these pages were freed. */
+ ULONG mo_txnid;
+ /** An #IDL of the pages */
+ pgno_t mo_pages[1]; /* dynamic */
+} MDB_oldpages;
+
+ /** The database environment. */
struct MDB_env {
- HANDLE me_fd;
- HANDLE me_lfd;
- HANDLE me_mfd; /* just for writing the meta pages */
+ HANDLE me_fd; /**< The main data file */
+ HANDLE me_lfd; /**< The lock file */
+ HANDLE me_mfd; /**< just for writing the meta pages */
#define MDB_FATAL_ERROR 0x80000000U
uint32_t me_flags;
- uint32_t me_extrapad; /* unused for now */
- unsigned int me_maxreaders;
- unsigned int me_numdbs;
- unsigned int me_maxdbs;
- char *me_path;
- char *me_map;
- MDB_txninfo *me_txns;
- MDB_meta *me_metas[2];
- MDB_txn *me_txn; /* current write transaction */
- size_t me_mapsize;
- off_t me_size; /* current file size */
- pgno_t me_maxpg; /* me_mapsize / me_psize */
- unsigned int me_psize;
- unsigned int me_db_toggle;
- MDB_dbx *me_dbxs; /* array */
- MDB_db *me_dbs[2];
- MDB_oldpages *me_pghead;
- pthread_key_t me_txkey; /* thread-key for readers */
- MDB_page *me_dpages;
+ uint32_t me_extrapad; /**< unused for now */
+ unsigned int me_maxreaders; /**< size of the reader table */
+ unsigned int me_numdbs; /**< number of DBs opened */
+ unsigned int me_maxdbs; /**< size of the DB table */
+ char *me_path; /**< path to the DB files */
+ char *me_map; /**< the memory map of the data file */
+ MDB_txninfo *me_txns; /**< the memory map of the lock file */
+ MDB_meta *me_metas[2]; /**< pointers to the two meta pages */
+ MDB_txn *me_txn; /**< current write transaction */
+ size_t me_mapsize; /**< size of the data memory map */
+ off_t me_size; /**< current file size */
+ pgno_t me_maxpg; /**< me_mapsize / me_psize */
+ unsigned int me_psize; /**< size of a page, from #GetPageSize */
+ unsigned int me_db_toggle; /**< which DB table is current */
+ MDB_dbx *me_dbxs; /**< array of static DB info */
+ MDB_db *me_dbs[2]; /**< two arrays of MDB_db info */
+ MDB_oldpages *me_pghead; /**< list of old page records */
+ pthread_key_t me_txkey; /**< thread-key for readers */
+ MDB_page *me_dpages; /**< list of malloc'd blocks for re-use */
+ /** IDL of pages that became unused in a write txn */
pgno_t me_free_pgs[MDB_IDL_UM_SIZE];
+ /** ID2L of pages that were written during a write txn */
ID2 me_dirty_list[MDB_IDL_UM_SIZE];
+ /** rwlock for the DB tables, if #LAZY_LOCKS is false */
LAZY_RWLOCK_DEF(me_dblock);
#ifdef _WIN32
HANDLE me_rmutex; /* Windows mutexes don't reside in shared mem */
HANDLE me_wmutex;
#endif
};
+ /** max number of pages to commit in one writev() call */
+#define MDB_COMMIT_PAGES 64
-#define NODESIZE offsetof(MDB_node, mn_data)
-
-#define INDXSIZE(k) (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))
-#define LEAFSIZE(k, d) (NODESIZE + (k)->mv_size + (d)->mv_size)
-#define NODEPTR(p, i) ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i]))
-#define NODEKEY(node) (void *)((node)->mn_data)
-#define NODEDATA(node) (void *)((char *)(node)->mn_data + (node)->mn_ksize)
-#if LONG_MAX == 0x7fffffff
-#define NODEPGNO(node) ((node)->mn_lo | ((node)->mn_hi << 16))
-#define SETPGNO(node,pgno) do { \
- (node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16;} while(0)
-#else
-#define NODEPGNO(node) ((node)->mn_lo | ((node)->mn_hi << 16) | ((unsigned long)(node)->mn_flags << 32))
-#define SETPGNO(node,pgno) do { \
- (node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
- (node)->mn_flags = (pgno) >> 32; } while(0)
-#endif
-#define NODEDSZ(node) ((node)->mn_lo | ((unsigned)(node)->mn_hi << 16))
-#define SETDSZ(node,size) do { \
- (node)->mn_lo = (size) & 0xffff; (node)->mn_hi = (size) >> 16;} while(0)
-#define NODEKSZ(node) ((node)->mn_ksize)
-#define LEAF2KEY(p, i, ks) ((char *)(p) + PAGEHDRSZ + ((i)*(ks)))
-
-#define MDB_SET_KEY(node, key) if (key!=NULL) {(key)->mv_size = NODEKSZ(node); (key)->mv_data = NODEKEY(node);}
-
-#define MDB_COMMIT_PAGES 64 /* max number of pages to write in one commit */
+static MDB_page *mdb_alloc_page(MDB_cursor *mc, int num);
+static int mdb_touch(MDB_cursor *mc);
static int mdb_search_page_root(MDB_cursor *mc,
MDB_val *key, int modify);
static void mdb_default_cmp(MDB_txn *txn, MDB_dbi dbi);
+/** @cond */
static MDB_cmp_func memncmp, memnrcmp, intcmp, cintcmp;
+/** @endcond */
#ifdef _WIN32
static SECURITY_DESCRIPTOR mdb_null_sd;
#endif
char *
-mdb_version(int *maj, int *min, int *pat)
+mdb_version(int *major, int *minor, int *patch)
{
- if (maj) *maj = MDB_VERSION_MAJOR;
- if (min) *min = MDB_VERSION_MINOR;
- if (pat) *pat = MDB_VERSION_PATCH;
+ if (major) *major = MDB_VERSION_MAJOR;
+ if (minor) *minor = MDB_VERSION_MINOR;
+ if (patch) *patch = MDB_VERSION_PATCH;
return MDB_VERSION_STRING;
}
+ /** Table of descriptions for MDB @ref error codes */
static char *const mdb_errstr[] = {
"MDB_KEYEXIST: Key/data pair already exists",
"MDB_NOTFOUND: No matching key/data pair found",
}
+ /** The name of the lock file in the DB environment */
#define LOCKNAME "/lock.mdb"
+ /** The name of the data file in the DB environment */
#define DATANAME "/data.mdb"
int
mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode)
}
}
-#define FILL_THRESHOLD 250
-
static int
mdb_rebalance(MDB_cursor *mc)
{
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