Commit 77d522d1 authored by Hallvard Furuseth's avatar Hallvard Furuseth
Browse files

Comment MDB_page

parent 8670805b
......@@ -868,9 +868,23 @@ typedef struct MDB_txninfo {
+ (((MDB_PIDLOCK) != 0) << 16)))
/** @} */
/** Common header for all page types.
* Overflow records occupy a number of contiguous pages with no
* headers on any page after the first.
/** 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.
*/
typedef struct MDB_page {
#define mp_pgno mp_p.p_pgno
......@@ -879,7 +893,7 @@ typedef struct MDB_page {
pgno_t p_pgno; /**< page number */
struct MDB_page *p_next; /**< for in-memory list of freed pages */
} mp_p;
uint16_t mp_pad;
uint16_t mp_pad; /**< key size if this is a LEAF2 page */
/** @defgroup mdb_page Page Flags
* @ingroup internal
* Flags for the page headers.
......@@ -946,7 +960,9 @@ typedef struct MDB_page {
/** The number of overflow pages needed to store the given size. */
#define OVPAGES(size, psize) ((PAGEHDRSZ-1 + (size)) / (psize) + 1)
/** Link in #MDB_txn.%mt_loose_pgs list */
/** Link in #MDB_txn.%mt_loose_pgs list.
* Kept outside the page header, which is needed when reusing the page.
*/
#define NEXT_LOOSE_PAGE(p) (*(MDB_page **)((p) + 2))
/** Header for a single key/data pair within a page.
......
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