Modules
	ID List Management

	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.

	Debug Macros

	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.

	Page Flags

	Node Flags

	Transaction DB Flags

	Transaction Flags

	Cursor Flags

Data Structures
struct	MDB_page

struct	MDB_node

struct	MDB_db

struct	MDB_meta

union	MDB_metabuf

struct	MDB_dbx

struct	MDB_txn
	Opaque structure for a transaction handle. More...

struct	MDB_cursor
	Opaque structure for navigating through a database. More...

struct	MDB_xcursor

struct	MDB_pgstate

struct	MDB_env
	Opaque structure for a database environment. More...

struct	MDB_ntxn

struct	MDB_name

struct	mdb_copy

Macros
#define	LOCK_MUTEX(rc, env, mutex) ((rc) = LOCK_MUTEX0(mutex))

#define	mdb_mutex_failed(env, mutex, rc) (rc)

#define	MDB_DSYNC O_SYNC

#define	MDB_FDATASYNC fdatasync

#define	MDB_MSYNC(addr, len, flags) msync(addr,len,flags)

#define	MS_SYNC 1

#define	MS_ASYNC 0

#define	MAX_PAGESIZE (PAGEBASE ? 0x10000 : 0x8000)
	The maximum size of a database page. More...

#define	MDB_MINKEYS 2

#define	MDB_MAGIC 0xBEEFC0DE

#define	MDB_DATA_VERSION ((MDB_DEVEL) ? 999 : 1)

#define	MDB_LOCK_VERSION 1

#define	MDB_MAXKEYSIZE ((MDB_DEVEL) ? 0 : 511)
	The max size of a key we can write, or 0 for computed max. More...

#define	ENV_MAXKEY(env) (MDB_MAXKEYSIZE)

#define	MAXDATASIZE 0xffffffffUL
	The maximum size of a data item. More...

#define	DKBUF

#define	DKEY(x) 0

#define	P_INVALID (~(pgno_t)0)

#define	F_ISSET(w, f) (((w) & (f)) == (f))

#define	EVEN(n) (((n) + 1U) & -2) /* sign-extending -2 to match n+1U */

#define	DEFAULT_MAPSIZE 1048576

#define	PAGEHDRSZ ((unsigned) offsetof(MDB_page, mp_ptrs))

#define	METADATA(p) ((void )((char )(p) + PAGEHDRSZ))

#define	PAGEBASE ((MDB_DEVEL) ? PAGEHDRSZ : 0)

#define	NUMKEYS(p) (((p)->mp_lower - (PAGEHDRSZ-PAGEBASE)) >> 1)

#define	SIZELEFT(p) (indx_t)((p)->mp_upper - (p)->mp_lower)

#define	PAGEFILL(env, p)

#define	FILL_THRESHOLD 250

#define	IS_LEAF(p) F_ISSET((p)->mp_flags, P_LEAF)

#define	IS_LEAF2(p) F_ISSET((p)->mp_flags, P_LEAF2)

#define	IS_BRANCH(p) F_ISSET((p)->mp_flags, P_BRANCH)

#define	IS_OVERFLOW(p) F_ISSET((p)->mp_flags, P_OVERFLOW)

#define	IS_SUBP(p) F_ISSET((p)->mp_flags, P_SUBP)

#define	OVPAGES(size, psize) ((PAGEHDRSZ-1 + (size)) / (psize) + 1)

#define	NEXT_LOOSE_PAGE(p) ((MDB_page *)((p) + 2))

#define	NODESIZE offsetof(MDB_node, mn_data)

#define	PGNO_TOPWORD ((pgno_t)-1 > 0xffffffffu ? 32 : 0)

#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] + PAGEBASE))

#define	NODEKEY(node) (void *)((node)->mn_data)

#define	NODEDATA(node) (void )((char )(node)->mn_data + (node)->mn_ksize)

#define	NODEPGNO(node)

#define	SETPGNO(node, pgno)

#define	NODEDSZ(node) ((node)->mn_lo \| ((unsigned)(node)->mn_hi << 16))

#define	SETDSZ(node, size)

#define	NODEKSZ(node) ((node)->mn_ksize)

#define	COPY_PGNO(dst, src)

#define	LEAF2KEY(p, i, ks) ((char )(p) + PAGEHDRSZ + ((i)(ks)))

#define	MDB_GET_KEY(node, keyptr)

#define	MDB_GET_KEY2(node, key) { key.mv_size = NODEKSZ(node); key.mv_data = NODEKEY(node); }

#define	MDB_VALID 0x8000

#define	PERSISTENT_FLAGS (0xffff & ~(MDB_VALID))

#define	VALID_FLAGS

#define	FREE_DBI 0

#define	MAIN_DBI 1

#define	CORE_DBS 2

#define	NUM_METAS 2

#define	CURSOR_STACK 32

#define	XCURSOR_INITED(mc) ((mc)->mc_xcursor && ((mc)->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED))

#define	XCURSOR_REFRESH(mc, top, mp)

#define	MDB_COMMIT_PAGES 64

#define	MAX_WRITE (0x40000000U >> (sizeof(ssize_t) == 4))

#define	TXN_DBI_EXIST(txn, dbi, validity) ((txn) && (dbi)<(txn)->mt_numdbs && ((txn)->mt_dbflags[dbi] & (validity)))

#define	TXN_DBI_CHANGED(txn, dbi) ((txn)->mt_dbiseqs[dbi] != (txn)->mt_env->me_dbiseqs[dbi])

#define	MDB_END_NAMES

#define	MDB_END_OPMASK 0x0F

#define	MDB_END_UPDATE 0x10

#define	MDB_END_FREE 0x20

#define	MDB_END_SLOT MDB_NOTLS

#define	MDB_PS_MODIFY 1

#define	MDB_PS_ROOTONLY 2

#define	MDB_PS_FIRST 4

#define	MDB_PS_LAST 8

#define	MDB_SPLIT_REPLACE MDB_APPENDDUP

#define	mdb_env_close0(env, excl) mdb_env_close1(env)

#define	mdb_cmp_clong mdb_cmp_cint

#define	mdb_cassert(mc, expr) mdb_assert0((mc)->mc_txn->mt_env, expr, #expr)

#define	mdb_tassert(txn, expr) mdb_assert0((txn)->mt_env, expr, #expr)

#define	mdb_eassert(env, expr) mdb_assert0(env, expr, #expr)

#define	mdb_assert0(env, expr, expr_txt)

#define	MDB_NAME(str) str

#define	mdb_name_cpy strcpy

#define	MDB_SUFFLEN 9

#define	mdb_fname_destroy(fname) do { if ((fname).mn_alloced) free((fname).mn_val); } while (0)

#define	MDB_CLOEXEC 0

#define	CHANGEABLE (MDB_NOSYNC\|MDB_NOMETASYNC\|MDB_MAPASYNC\|MDB_NOMEMINIT)

#define	CHANGELESS

#define	MDB_NOSPILL 0x8000

#define	WITH_CURSOR_TRACKING(mn, act)

#define	MDB_WBUF (1024*1024)

#define	MDB_EOF 0x10

Typedefs
typedef MDB_ID	pgno_t

typedef MDB_ID	txnid_t

typedef uint16_t	indx_t

typedef char	mdb_nchar_t

Enumerations
enum	{ MDB_END_COMMITTED, MDB_END_EMPTY_COMMIT, MDB_END_ABORT, MDB_END_RESET, MDB_END_RESET_TMP, MDB_END_FAIL_BEGIN, MDB_END_FAIL_BEGINCHILD }

enum	Pidlock_op { Pidset = F_SETLK, Pidcheck = F_GETLK }

enum	mdb_fopen_type { MDB_O_RDONLY = O_RDONLY, MDB_O_RDWR = O_RDWR \|O_CREAT, MDB_O_META = O_WRONLY\|MDB_DSYNC \|MDB_CLOEXEC, MDB_O_COPY = O_WRONLY\|O_CREAT\|O_EXCL\|MDB_CLOEXEC, MDB_O_MASK = MDB_O_RDWR\|MDB_CLOEXEC \| MDB_O_RDONLY\|MDB_O_META\|MDB_O_COPY, MDB_O_LOCKS = MDB_O_RDWR\|MDB_CLOEXEC \| ((MDB_O_MASK+1) & ~MDB_O_MASK) }

Functions
static int	mdb_page_alloc (MDB_cursor mc, int num, MDB_page *mp)

static int	mdb_page_new (MDB_cursor mc, uint32_t flags, int num, MDB_page *mp)

static int	mdb_page_touch (MDB_cursor *mc)

static void	mdb_txn_end (MDB_txn *txn, unsigned mode)

static int	mdb_page_get (MDB_cursor mc, pgno_t pgno, MDB_page mp, int lvl)

static int	mdb_page_search_root (MDB_cursor mc, MDB_val key, int modify)

static int	mdb_page_search (MDB_cursor mc, MDB_val key, int flags)

static int	mdb_page_merge (MDB_cursor csrc, MDB_cursor cdst)

static int	mdb_page_split (MDB_cursor mc, MDB_val newkey, MDB_val *newdata, pgno_t newpgno, unsigned int nflags)

static int	mdb_env_read_header (MDB_env env, MDB_meta meta)

static MDB_meta *	mdb_env_pick_meta (const MDB_env *env)

static int	mdb_env_write_meta (MDB_txn *txn)

static void	mdb_env_close0 (MDB_env *env, int excl)

static MDB_node *	mdb_node_search (MDB_cursor mc, MDB_val key, int *exactp)

static int	mdb_node_add (MDB_cursor mc, indx_t indx, MDB_val key, MDB_val *data, pgno_t pgno, unsigned int flags)

static void	mdb_node_del (MDB_cursor *mc, int ksize)

static void	mdb_node_shrink (MDB_page *mp, indx_t indx)

static int	mdb_node_move (MDB_cursor csrc, MDB_cursor cdst, int fromleft)

static int	mdb_node_read (MDB_cursor mc, MDB_node leaf, MDB_val *data)

static size_t	mdb_leaf_size (MDB_env env, MDB_val key, MDB_val *data)

static size_t	mdb_branch_size (MDB_env env, MDB_val key)

static int	mdb_rebalance (MDB_cursor *mc)

static int	mdb_update_key (MDB_cursor mc, MDB_val key)

static void	mdb_cursor_pop (MDB_cursor *mc)

static int	mdb_cursor_push (MDB_cursor mc, MDB_page mp)

static int	mdb_cursor_del0 (MDB_cursor *mc)

static int	mdb_del0 (MDB_txn txn, MDB_dbi dbi, MDB_val key, MDB_val *data, unsigned flags)

static int	mdb_cursor_sibling (MDB_cursor *mc, int move_right)

static int	mdb_cursor_next (MDB_cursor mc, MDB_val key, MDB_val *data, MDB_cursor_op op)

static int	mdb_cursor_prev (MDB_cursor mc, MDB_val key, MDB_val *data, MDB_cursor_op op)

static int	mdb_cursor_set (MDB_cursor mc, MDB_val key, MDB_val data, MDB_cursor_op op, int exactp)

static int	mdb_cursor_first (MDB_cursor mc, MDB_val key, MDB_val *data)

static int	mdb_cursor_last (MDB_cursor mc, MDB_val key, MDB_val *data)

static void	mdb_cursor_init (MDB_cursor mc, MDB_txn txn, MDB_dbi dbi, MDB_xcursor *mx)

static void	mdb_xcursor_init0 (MDB_cursor *mc)

static void	mdb_xcursor_init1 (MDB_cursor mc, MDB_node node)

static void	mdb_xcursor_init2 (MDB_cursor mc, MDB_xcursor src_mx, int force)

static int	mdb_drop0 (MDB_cursor *mc, int subs)

static void	mdb_default_cmp (MDB_txn *txn, MDB_dbi dbi)

static int	mdb_reader_check0 (MDB_env env, int rlocked, int dead)

char *ESECT	mdb_version (int major, int minor, int *patch)
	Return the LMDB library version information. More...

char *	mdb_strerror (int err)
	Return a string describing a given error code. More...

static void ESECT	mdb_assert_fail (MDB_env env, const char expr_txt, const char func, const char file, int line)

int	mdb_cmp (MDB_txn txn, MDB_dbi dbi, const MDB_val a, const MDB_val *b)
	Compare two data items according to a particular database. More...

int	mdb_dcmp (MDB_txn txn, MDB_dbi dbi, const MDB_val a, const MDB_val *b)
	Compare two data items according to a particular database. More...

static MDB_page *	mdb_page_malloc (MDB_txn *txn, unsigned num)

static void	mdb_page_free (MDB_env env, MDB_page mp)

static void	mdb_dpage_free (MDB_env env, MDB_page dp)

static void	mdb_dlist_free (MDB_txn *txn)

static int	mdb_page_loose (MDB_cursor mc, MDB_page mp)

static int	mdb_pages_xkeep (MDB_cursor *mc, unsigned pflags, int all)

static int	mdb_page_flush (MDB_txn *txn, int keep)

static int	mdb_page_spill (MDB_cursor m0, MDB_val key, MDB_val *data)

static txnid_t	mdb_find_oldest (MDB_txn *txn)

static void	mdb_page_dirty (MDB_txn txn, MDB_page mp)

static void	mdb_page_copy (MDB_page dst, MDB_page src, unsigned int psize)

static int	mdb_page_unspill (MDB_txn txn, MDB_page mp, MDB_page **ret)

int	mdb_env_sync (MDB_env *env, int force)
	Flush the data buffers to disk. More...

static int	mdb_cursor_shadow (MDB_txn src, MDB_txn dst)

static void	mdb_cursors_close (MDB_txn *txn, unsigned merge)

static int	mdb_reader_pid (MDB_env *env, enum Pidlock_op op, MDB_PID_T pid)

static int	mdb_txn_renew0 (MDB_txn *txn)

int	mdb_txn_renew (MDB_txn *txn)
	Renew a read-only transaction. More...

int	mdb_txn_begin (MDB_env env, MDB_txn parent, unsigned int flags, MDB_txn **ret)
	Create a transaction for use with the environment. More...

MDB_env *	mdb_txn_env (MDB_txn *txn)
	Returns the transaction's MDB_env. More...

size_t	mdb_txn_id (MDB_txn *txn)
	Return the transaction's ID. More...

static void	mdb_dbis_update (MDB_txn *txn, int keep)

void	mdb_txn_reset (MDB_txn *txn)
	Reset a read-only transaction. More...

void	mdb_txn_abort (MDB_txn *txn)
	Abandon all the operations of the transaction instead of saving them. More...

static int	mdb_freelist_save (MDB_txn *txn)

int	mdb_txn_commit (MDB_txn *txn)
	Commit all the operations of a transaction into the database. More...

static void ESECT	mdb_env_init_meta0 (MDB_env env, MDB_meta meta)

static int ESECT	mdb_env_init_meta (MDB_env env, MDB_meta meta)

int ESECT	mdb_env_create (MDB_env **env)
	Create an LMDB environment handle. More...

static int ESECT	mdb_env_map (MDB_env env, void addr)

int ESECT	mdb_env_set_mapsize (MDB_env *env, size_t size)
	Set the size of the memory map to use for this environment. More...

int ESECT	mdb_env_set_maxdbs (MDB_env *env, MDB_dbi dbs)
	Set the maximum number of named databases for the environment. More...

int ESECT	mdb_env_set_maxreaders (MDB_env *env, unsigned int readers)
	Set the maximum number of threads/reader slots for the environment. More...

int ESECT	mdb_env_get_maxreaders (MDB_env env, unsigned int readers)
	Get the maximum number of threads/reader slots for the environment. More...

static int ESECT	mdb_fsize (HANDLE fd, size_t *size)

static int ESECT	mdb_fname_init (const char path, unsigned envflags, MDB_name fname)

static int ESECT	mdb_fopen (const MDB_env env, MDB_name fname, enum mdb_fopen_type which, mdb_mode_t mode, HANDLE *res)

static int ESECT	mdb_env_open2 (MDB_env *env)

static void	mdb_env_reader_dest (void *ptr)

static int ESECT	mdb_env_share_locks (MDB_env env, int excl)

static int ESECT	mdb_env_excl_lock (MDB_env env, int excl)

static int ESECT	mdb_env_setup_locks (MDB_env env, MDB_name fname, int mode, int *excl)

int ESECT	mdb_env_open (MDB_env env, const char path, unsigned int flags, mdb_mode_t mode)
	Open an environment handle. More...

void ESECT	mdb_env_close (MDB_env *env)
	Close the environment and release the memory map. More...

static int	mdb_cmp_long (const MDB_val a, const MDB_val b)

static int	mdb_cmp_int (const MDB_val a, const MDB_val b)

static int	mdb_cmp_cint (const MDB_val a, const MDB_val b)

static int	mdb_cmp_memn (const MDB_val a, const MDB_val b)

static int	mdb_cmp_memnr (const MDB_val a, const MDB_val b)

static int	mdb_page_search_lowest (MDB_cursor *mc)

static int	mdb_ovpage_free (MDB_cursor mc, MDB_page mp)

int	mdb_get (MDB_txn txn, MDB_dbi dbi, MDB_val key, MDB_val *data)
	Get items from a database. More...

int	mdb_cursor_get (MDB_cursor mc, MDB_val key, MDB_val *data, MDB_cursor_op op)
	Retrieve by cursor. More...

static int	mdb_cursor_touch (MDB_cursor *mc)

int	mdb_cursor_put (MDB_cursor mc, MDB_val key, MDB_val *data, unsigned int flags)
	Store by cursor. More...

int	mdb_cursor_del (MDB_cursor *mc, unsigned int flags)
	Delete current key/data pair. More...

int	mdb_cursor_open (MDB_txn txn, MDB_dbi dbi, MDB_cursor *ret)
	Create a cursor handle. More...

int	mdb_cursor_renew (MDB_txn txn, MDB_cursor mc)
	Renew a cursor handle. More...

int	mdb_cursor_count (MDB_cursor mc, size_t countp)
	Return count of duplicates for current key. More...

void	mdb_cursor_close (MDB_cursor *mc)
	Close a cursor handle. More...

MDB_txn *	mdb_cursor_txn (MDB_cursor *mc)
	Return the cursor's transaction handle. More...

MDB_dbi	mdb_cursor_dbi (MDB_cursor *mc)
	Return the cursor's database handle. More...

static void	mdb_cursor_copy (const MDB_cursor csrc, MDB_cursor cdst)

int	mdb_del (MDB_txn txn, MDB_dbi dbi, MDB_val key, MDB_val *data)
	Delete items from a database. More...

int	mdb_put (MDB_txn txn, MDB_dbi dbi, MDB_val key, MDB_val *data, unsigned int flags)
	Store items into a database. More...

static THREAD_RET ESECT CALL_CONV	mdb_env_copythr (void *arg)

static int ESECT	mdb_env_cthr_toggle (mdb_copy *my, int adjust)

static int ESECT	mdb_env_cwalk (mdb_copy my, pgno_t pg, int flags)

static int ESECT	mdb_env_copyfd1 (MDB_env *env, HANDLE fd)

static int ESECT	mdb_env_copyfd0 (MDB_env *env, HANDLE fd)

int ESECT	mdb_env_copyfd2 (MDB_env *env, HANDLE fd, unsigned int flags)

int ESECT	mdb_env_copyfd (MDB_env *env, HANDLE fd)

int ESECT	mdb_env_copy2 (MDB_env env, const char path, unsigned int flags)
	Copy an LMDB environment to the specified path, with options. More...

int ESECT	mdb_env_copy (MDB_env env, const char path)
	Copy an LMDB environment to the specified path. More...

int ESECT	mdb_env_set_flags (MDB_env *env, unsigned int flag, int onoff)
	Set environment flags. More...

int ESECT	mdb_env_get_flags (MDB_env env, unsigned int arg)
	Get environment flags. More...

int ESECT	mdb_env_set_userctx (MDB_env env, void ctx)
	Set application information associated with the MDB_env. More...

void *ESECT	mdb_env_get_userctx (MDB_env *env)
	Get the application information associated with the MDB_env. More...

int ESECT	mdb_env_set_assert (MDB_env env, MDB_assert_func func)

int ESECT	mdb_env_get_path (MDB_env env, const char *arg)
	Return the path that was used in mdb_env_open(). More...

int ESECT	mdb_env_get_fd (MDB_env env, mdb_filehandle_t arg)
	Return the filedescriptor for the given environment. More...

static int ESECT	mdb_stat0 (MDB_env env, MDB_db db, MDB_stat *arg)

int ESECT	mdb_env_stat (MDB_env env, MDB_stat arg)
	Return statistics about the LMDB environment. More...

int ESECT	mdb_env_info (MDB_env env, MDB_envinfo arg)
	Return information about the LMDB environment. More...

int	mdb_dbi_open (MDB_txn txn, const char name, unsigned int flags, MDB_dbi *dbi)
	Open a database in the environment. More...

int ESECT	mdb_stat (MDB_txn txn, MDB_dbi dbi, MDB_stat arg)
	Retrieve statistics for a database. More...

void	mdb_dbi_close (MDB_env *env, MDB_dbi dbi)
	Close a database handle. Normally unnecessary. Use with care: More...

int	mdb_dbi_flags (MDB_txn txn, MDB_dbi dbi, unsigned int flags)
	Retrieve the DB flags for a database handle. More...

int	mdb_drop (MDB_txn *txn, MDB_dbi dbi, int del)
	Empty or delete+close a database. More...

int	mdb_set_compare (MDB_txn txn, MDB_dbi dbi, MDB_cmp_func cmp)
	Set a custom key comparison function for a database. More...

int	mdb_set_dupsort (MDB_txn txn, MDB_dbi dbi, MDB_cmp_func cmp)
	Set a custom data comparison function for a MDB_DUPSORT database. More...

int	mdb_set_relfunc (MDB_txn txn, MDB_dbi dbi, MDB_rel_func rel)
	Set a relocation function for a MDB_FIXEDMAP database. More...

int	mdb_set_relctx (MDB_txn txn, MDB_dbi dbi, void ctx)
	Set a context pointer for a MDB_FIXEDMAP database's relocation function. More...

int ESECT	mdb_env_get_maxkeysize (MDB_env *env)
	Get the maximum size of keys and MDB_DUPSORT data we can write. More...

int ESECT	mdb_reader_list (MDB_env env, MDB_msg_func func, void *ctx)
	Dump the entries in the reader lock table. More...

static int ESECT	mdb_pid_insert (MDB_PID_T *ids, MDB_PID_T pid)

int ESECT	mdb_reader_check (MDB_env env, int dead)
	Check for stale entries in the reader lock table. More...

Variables
static char *const	mdb_errstr []

static const mdb_nchar_t *const	mdb_suffixes [2][2]

Detailed Description

Data Structure Documentation

◆ MDB_page

struct MDB_page

Common header for all page types. The page type depends on mp_flags.

P_BRANCH and P_LEAF pages have unsorted 'MDB_node's at the end, with sorted mp_ptrs[] entries referring to them. Exception: P_LEAF2 pages omit mp_ptrs and pack sorted MDB_DUPFIXED values after the page header.

P_OVERFLOW records occupy one or more contiguous pages where only the first has a page header. They hold the real data of F_BIGDATA nodes.

P_SUBP sub-pages are small leaf "pages" with duplicate data. A node with flag F_DUPDATA but not F_SUBDATA contains a sub-page. (Duplicate data can also go in sub-databases, which use normal pages.)

P_META pages contain MDB_meta, the start point of an LMDB snapshot.

Each non-metapage up to MDB_meta.mm_last_pg is reachable exactly once in the snapshot: Either used by a database or listed in a freeDB record.

Data Fields
union {
pgno_t p_pgno

struct MDB_page * p_next

}	mp_p

uint16_t	mp_pad

uint16_t	mp_flags

union {
struct {
indx_t pb_lower

indx_t pb_upper

} pb

uint32_t pb_pages

}	mp_pb

indx_t	mp_ptrs [1]

Field Documentation

◆ p_pgno

pgno_t MDB_page::p_pgno

page number

◆ p_next

struct MDB_page* MDB_page::p_next

for in-memory list of freed pages

◆ mp_pad

uint16_t MDB_page::mp_pad

key size if this is a LEAF2 page

◆ mp_flags

uint16_t MDB_page::mp_flags

Page Flags

◆ pb_lower

indx_t MDB_page::pb_lower

lower bound of free space

◆ pb_upper

indx_t MDB_page::pb_upper

upper bound of free space

◆ pb_pages

uint32_t MDB_page::pb_pages

number of overflow pages

◆ mp_ptrs

indx_t MDB_page::mp_ptrs[1]

dynamic size

◆ MDB_node

struct MDB_node

Header for a single key/data pair within a page. Used in pages of type P_BRANCH and P_LEAF without P_LEAF2. We guarantee 2-byte alignment for 'MDB_node's.

mn_lo and mn_hi are used for data size on leaf nodes, and for child pgno on branch nodes. On 64 bit platforms, mn_flags is also used for pgno. (Branch nodes have no flags). Lo and hi are in host byte order in case some accesses can be optimized to 32-bit word access.

Leaf node flags describe node contents. F_BIGDATA says the node's data part is the page number of an overflow page with actual data. F_DUPDATA and F_SUBDATA can be combined giving duplicate data in a sub-page/sub-database, and named databases (just F_SUBDATA).

Data Fields
unsigned short	mn_flags

unsigned short	mn_ksize

char	mn_data [1]


unsigned short	mn_lo

unsigned short	mn_hi

Field Documentation

◆ mn_lo

unsigned short MDB_node::mn_lo

part of data size or pgno

◆ mn_hi

unsigned short MDB_node::mn_hi

part of data size or pgno

◆ mn_flags

unsigned short MDB_node::mn_flags

Node Flags

◆ mn_ksize

unsigned short MDB_node::mn_ksize

key size

◆ mn_data

char MDB_node::mn_data[1]

key and data are appended here

◆ MDB_db

struct MDB_db

Information about a single database in the environment.

Data Fields
uint32_t	md_pad

uint16_t	md_flags

uint16_t	md_depth

pgno_t	md_branch_pages

pgno_t	md_leaf_pages

pgno_t	md_overflow_pages

size_t	md_entries

pgno_t	md_root

Field Documentation

◆ md_pad

uint32_t MDB_db::md_pad

also ksize for LEAF2 pages

◆ md_flags

uint16_t MDB_db::md_flags

Database Flags

◆ md_depth

uint16_t MDB_db::md_depth

depth of this tree

◆ md_branch_pages

pgno_t MDB_db::md_branch_pages

number of internal pages

◆ md_leaf_pages

pgno_t MDB_db::md_leaf_pages

number of leaf pages

◆ md_overflow_pages

pgno_t MDB_db::md_overflow_pages

number of overflow pages

◆ md_entries

size_t MDB_db::md_entries

number of data items

◆ md_root

pgno_t MDB_db::md_root

the root page of this tree

◆ MDB_meta

struct MDB_meta

Meta page content. A meta page is the start point for accessing a database snapshot. Pages 0-1 are meta pages. Transaction N writes meta page #(N % 2).

Data Fields
uint32_t	mm_magic

uint32_t	mm_version

void *	mm_address

size_t	mm_mapsize

MDB_db	mm_dbs [CORE_DBS]

pgno_t	mm_last_pg

volatile txnid_t	mm_txnid

Field Documentation

◆ mm_magic

uint32_t MDB_meta::mm_magic

Stamp identifying this as an LMDB file. It must be set to MDB_MAGIC.

◆ mm_version

uint32_t MDB_meta::mm_version

Version number of this file. Must be set to MDB_DATA_VERSION.

◆ mm_address

void* MDB_meta::mm_address

address for fixed mapping

◆ mm_mapsize

size_t MDB_meta::mm_mapsize

size of mmap region

◆ mm_dbs

MDB_db MDB_meta::mm_dbs[CORE_DBS]

first is free space, 2nd is main db

◆ mm_last_pg

pgno_t MDB_meta::mm_last_pg

Last used page in the datafile. Actually the file may be shorter if the freeDB lists the final pages.

◆ mm_txnid

volatile txnid_t MDB_meta::mm_txnid

txnid that committed this page

◆ MDB_metabuf

union MDB_metabuf

Buffer for a stack-allocated meta page. The members define size and alignment, and silence type aliasing warnings. They are not used directly; that could mean incorrectly using several union members in parallel.

Data Fields
MDB_page	mb_page

struct {
char mm_pad [PAGEHDRSZ]

MDB_meta mm_meta

}	mb_metabuf

◆ MDB_dbx

struct MDB_dbx

Auxiliary DB info. The information here is mostly static/read-only. There is only a single copy of this record in the environment.

Data Fields
MDB_val	md_name

MDB_cmp_func *	md_cmp

MDB_cmp_func *	md_dcmp

MDB_rel_func *	md_rel

void *	md_relctx

Field Documentation

◆ md_name

MDB_val MDB_dbx::md_name

name of the database

◆ md_cmp

MDB_cmp_func* MDB_dbx::md_cmp

function for comparing keys

◆ md_dcmp

MDB_cmp_func* MDB_dbx::md_dcmp

function for comparing data items

◆ md_rel

MDB_rel_func* MDB_dbx::md_rel

user relocate function

◆ md_relctx

void* MDB_dbx::md_relctx

user-provided context for md_rel

◆ MDB_txn

struct MDB_txn

Opaque structure for a transaction handle.

A database transaction. Every operation requires a transaction handle.

All database operations require a transaction handle. Transactions may be read-only or read-write.

Data Fields
MDB_txn *	mt_parent

MDB_txn *	mt_child

pgno_t	mt_next_pgno

txnid_t	mt_txnid

MDB_env *	mt_env

MDB_IDL	mt_free_pgs

MDB_page *	mt_loose_pgs

int	mt_loose_count

MDB_IDL	mt_spill_pgs

union {
MDB_ID2L dirty_list

MDB_reader * reader

}	mt_u

MDB_dbx *	mt_dbxs

MDB_db *	mt_dbs

unsigned int *	mt_dbiseqs

MDB_cursor **	mt_cursors

unsigned char *	mt_dbflags

MDB_dbi	mt_numdbs

unsigned int	mt_flags

unsigned int	mt_dirty_room

Modules

Data Structures

Macros

Typedefs

Enumerations

Functions

Variables

Detailed Description

Data Structure Documentation

◆ MDB_page

Data Fields

Field Documentation

◆ p_pgno

◆ p_next

◆ mp_pad

◆ mp_flags

◆ pb_lower

◆ pb_upper

◆ pb_pages

◆ mp_ptrs

◆ MDB_node

Data Fields

Field Documentation

◆ mn_lo

◆ mn_hi

◆ mn_flags

◆ mn_ksize

◆ mn_data

◆ MDB_db

Data Fields

Field Documentation

◆ md_pad

◆ md_flags

◆ md_depth

◆ md_branch_pages

◆ md_leaf_pages

◆ md_overflow_pages

◆ md_entries

◆ md_root

◆ MDB_meta

Data Fields

Field Documentation

◆ mm_magic

◆ mm_version

◆ mm_address

◆ mm_mapsize

◆ mm_dbs

◆ mm_last_pg

◆ mm_txnid

◆ MDB_metabuf

Data Fields

◆ MDB_dbx

Data Fields

Field Documentation

◆ md_name

◆ md_cmp

◆ md_dcmp

◆ md_rel

◆ md_relctx

◆ MDB_txn

Data Fields

Field Documentation