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gecko-dev/db/include/db_page.h
roeber%netscape.com feaefda4fa Import of Sleepycat DB 2.4.14.1
1998-10-15 03:56:37 +00:00

563 lines
20 KiB
C
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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996, 1997, 1998
* Sleepycat Software. All rights reserved.
*
* @(#)db_page.h 10.15 (Sleepycat) 5/1/98
*/
#ifndef _DB_PAGE_H_
#define _DB_PAGE_H_
/*
* DB page formats.
*
* This implementation requires that values within the following structures
* NOT be padded -- note, ANSI C permits random padding within structures.
* If your compiler pads randomly you can just forget ever making DB run on
* your system. In addition, no data type can require larger alignment than
* its own size, e.g., a 4-byte data element may not require 8-byte alignment.
*
* Note that key/data lengths are often stored in db_indx_t's -- this is
* not accidental, nor does it limit the key/data size. If the key/data
* item fits on a page, it's guaranteed to be small enough to fit into a
* db_indx_t, and storing it in one saves space.
*/
#define PGNO_METADATA 0 /* Metadata page number. */
#define PGNO_INVALID 0 /* Metadata page number, therefore illegal. */
#define PGNO_ROOT 1 /* Root is page #1. */
/*
* When we create pages in mpool, we ask mpool to clear some number of bytes
* in the header. This number must be at least as big as the regular page
* headers and cover enough of the btree and hash meta-data pages to obliterate
* the magic and version numbers.
*/
#define DB_PAGE_CLEAR_LEN 32
/************************************************************************
BTREE METADATA PAGE LAYOUT
************************************************************************/
/*
* Btree metadata page layout:
*
* +-----------------------------------+
* | lsn | pgno | magic |
* +-----------------------------------+
* | version | pagesize | free |
* +-----------------------------------+
* | flags | unused ... |
* +-----------------------------------+
*/
typedef struct _btmeta {
DB_LSN lsn; /* 00-07: LSN. */
db_pgno_t pgno; /* 08-11: Current page number. */
u_int32_t magic; /* 12-15: Magic number. */
u_int32_t version; /* 16-19: Version. */
u_int32_t pagesize; /* 20-23: Pagesize. */
u_int32_t maxkey; /* 24-27: Btree: Maxkey. */
u_int32_t minkey; /* 28-31: Btree: Minkey. */
u_int32_t free; /* 32-35: Free list page number. */
#define BTM_DUP 0x001 /* Duplicates. */
#define BTM_RECNO 0x002 /* Recno tree. */
#define BTM_RECNUM 0x004 /* Btree: maintain record count. */
#define BTM_FIXEDLEN 0x008 /* Recno: fixed length records. */
#define BTM_RENUMBER 0x010 /* Recno: renumber on insert/delete. */
#define BTM_MASK 0x01f
u_int32_t flags; /* 36-39: Flags. */
u_int32_t re_len; /* 40-43: Recno: fixed-length record length. */
u_int32_t re_pad; /* 44-47: Recno: fixed-length record pad. */
/* 48-67: Unique file ID. */
u_int8_t uid[DB_FILE_ID_LEN];
u_int32_t spare[13]; /* 68-123: Save some room for growth. */
DB_BTREE_LSTAT stat; /* 124-163: Statistics. */
} BTMETA;
/************************************************************************
HASH METADATA PAGE LAYOUT
************************************************************************/
/*
* Hash metadata page layout:
*
* +-----------------------------------+
* | lsn | magic | version |
* +-----------------------------------+
* | pagesize | ovfl_point| last_freed|
* +-----------------------------------+
* | max_bucket| high_mask | low_mask |
* +-----------------------------------+
* | ffactor | nelem | charkey |
* +-----------------------------------+
* | spares[32]| flags | unused |
* +-----------------------------------+
*/
/* Hash Table Information */
typedef struct hashhdr { /* Disk resident portion */
DB_LSN lsn; /* 00-07: LSN of the header page */
db_pgno_t pgno; /* 08-11: Page number (btree compatibility). */
u_int32_t magic; /* 12-15: Magic NO for hash tables */
u_int32_t version; /* 16-19: Version ID */
u_int32_t pagesize; /* 20-23: Bucket/Page Size */
u_int32_t ovfl_point; /* 24-27: Overflow page allocation location */
u_int32_t last_freed; /* 28-31: Last freed overflow page pgno */
u_int32_t max_bucket; /* 32-35: ID of Maximum bucket in use */
u_int32_t high_mask; /* 36-39: Modulo mask into table */
u_int32_t low_mask; /* 40-43: Modulo mask into table lower half */
u_int32_t ffactor; /* 44-47: Fill factor */
u_int32_t nelem; /* 48-51: Number of keys in hash table */
u_int32_t h_charkey; /* 52-55: Value of hash(CHARKEY) */
#define DB_HASH_DUP 0x01
u_int32_t flags; /* 56-59: Allow duplicates. */
#define NCACHED 32 /* number of spare points */
/* 60-187: Spare pages for overflow */
u_int32_t spares[NCACHED];
/* 188-207: Unique file ID. */
u_int8_t uid[DB_FILE_ID_LEN];
/*
* Minimum page size is 256.
*/
} HASHHDR;
/************************************************************************
MAIN PAGE LAYOUT
************************************************************************/
/*
* +-----------------------------------+
* | lsn | pgno | prev pgno |
* +-----------------------------------+
* | next pgno | entries | hf offset |
* +-----------------------------------+
* | level | type | index |
* +-----------------------------------+
* | index | free --> |
* +-----------+-----------------------+
* | F R E E A R E A |
* +-----------------------------------+
* | <-- free | item |
* +-----------------------------------+
* | item | item | item |
* +-----------------------------------+
*
* sizeof(PAGE) == 26 bytes, and the following indices are guaranteed to be
* two-byte aligned.
*
* For hash and btree leaf pages, index items are paired, e.g., inp[0] is the
* key for inp[1]'s data. All other types of pages only contain single items.
*/
typedef struct _db_page {
DB_LSN lsn; /* 00-07: Log sequence number. */
db_pgno_t pgno; /* 08-11: Current page number. */
db_pgno_t prev_pgno; /* 12-15: Previous page number. */
db_pgno_t next_pgno; /* 16-19: Next page number. */
db_indx_t entries; /* 20-21: Number of item pairs on the page. */
db_indx_t hf_offset; /* 22-23: High free byte page offset. */
/*
* The btree levels are numbered from the leaf to the root, starting
* with 1, so the leaf is level 1, its parent is level 2, and so on.
* We maintain this level on all btree pages, but the only place that
* we actually need it is on the root page. It would not be difficult
* to hide the byte on the root page once it becomes an internal page,
* so we could get this byte back if we needed it for something else.
*/
#define LEAFLEVEL 1
#define MAXBTREELEVEL 255
u_int8_t level; /* 24: Btree tree level. */
#define P_INVALID 0 /* Invalid page type. */
#define P_DUPLICATE 1 /* Duplicate. */
#define P_HASH 2 /* Hash. */
#define P_IBTREE 3 /* Btree internal. */
#define P_IRECNO 4 /* Recno internal. */
#define P_LBTREE 5 /* Btree leaf. */
#define P_LRECNO 6 /* Recno leaf. */
#define P_OVERFLOW 7 /* Overflow. */
u_int8_t type; /* 25: Page type. */
db_indx_t inp[1]; /* Variable length index of items. */
} PAGE;
/* Element macros. */
#define LSN(p) (((PAGE *)p)->lsn)
#define PGNO(p) (((PAGE *)p)->pgno)
#define PREV_PGNO(p) (((PAGE *)p)->prev_pgno)
#define NEXT_PGNO(p) (((PAGE *)p)->next_pgno)
#define NUM_ENT(p) (((PAGE *)p)->entries)
#define HOFFSET(p) (((PAGE *)p)->hf_offset)
#define LEVEL(p) (((PAGE *)p)->level)
#define TYPE(p) (((PAGE *)p)->type)
/*
* !!!
* The next_pgno and prev_pgno fields are not maintained for btree and recno
* internal pages. It's a minor performance improvement, and more, it's
* hard to do when deleting internal pages, and it decreases the chance of
* deadlock during deletes and splits.
*
* !!!
* The btree/recno access method needs db_recno_t bytes of space on the root
* page to specify how many records are stored in the tree. (The alternative
* is to store the number of records in the meta-data page, which will create
* a second hot spot in trees being actively modified, or recalculate it from
* the BINTERNAL fields on each access.) Overload the prev_pgno field.
*/
#define RE_NREC(p) \
(TYPE(p) == P_LBTREE ? NUM_ENT(p) / 2 : \
TYPE(p) == P_LRECNO ? NUM_ENT(p) : PREV_PGNO(p))
#define RE_NREC_ADJ(p, adj) \
PREV_PGNO(p) += adj;
#define RE_NREC_SET(p, num) \
PREV_PGNO(p) = num;
/*
* Initialize a page.
*
* !!!
* Don't modify the page's LSN, code depends on it being unchanged after a
* P_INIT call.
*/
#define P_INIT(pg, pg_size, n, pg_prev, pg_next, btl, pg_type) do { \
PGNO(pg) = n; \
PREV_PGNO(pg) = pg_prev; \
NEXT_PGNO(pg) = pg_next; \
NUM_ENT(pg) = 0; \
HOFFSET(pg) = pg_size; \
LEVEL(pg) = btl; \
TYPE(pg) = pg_type; \
} while (0)
/* Page header length (offset to first index). */
#define P_OVERHEAD (SSZA(PAGE, inp))
/* First free byte. */
#define LOFFSET(pg) (P_OVERHEAD + NUM_ENT(pg) * sizeof(db_indx_t))
/* Free space on the page. */
#define P_FREESPACE(pg) (HOFFSET(pg) - LOFFSET(pg))
/* Get a pointer to the bytes at a specific index. */
#define P_ENTRY(pg, indx) ((u_int8_t *)pg + ((PAGE *)pg)->inp[indx])
/************************************************************************
OVERFLOW PAGE LAYOUT
************************************************************************/
/*
* Overflow items are referenced by HOFFPAGE and BOVERFLOW structures, which
* store a page number (the first page of the overflow item) and a length
* (the total length of the overflow item). The overflow item consists of
* some number of overflow pages, linked by the next_pgno field of the page.
* A next_pgno field of PGNO_INVALID flags the end of the overflow item.
*
* Overflow page overloads:
* The amount of overflow data stored on each page is stored in the
* hf_offset field.
*
* The implementation reference counts overflow items as it's possible
* for them to be promoted onto btree internal pages. The reference
* count is stored in the entries field.
*/
#define OV_LEN(p) (((PAGE *)p)->hf_offset)
#define OV_REF(p) (((PAGE *)p)->entries)
/* Maximum number of bytes that you can put on an overflow page. */
#define P_MAXSPACE(psize) ((psize) - P_OVERHEAD)
/************************************************************************
HASH PAGE LAYOUT
************************************************************************/
/* Each index references a group of bytes on the page. */
#define H_KEYDATA 1 /* Key/data item. */
#define H_DUPLICATE 2 /* Duplicate key/data item. */
#define H_OFFPAGE 3 /* Overflow key/data item. */
#define H_OFFDUP 4 /* Overflow page of duplicates. */
/*
* !!!
* Items on hash pages are (potentially) unaligned, so we can never cast the
* (page + offset) pointer to an HKEYDATA, HOFFPAGE or HOFFDUP structure, as
* we do with B+tree on-page structures. Because we frequently want the type
* field, it requires no alignment, and it's in the same location in all three
* structures, there's a pair of macros.
*/
#define HPAGE_PTYPE(p) (*(u_int8_t *)p)
#define HPAGE_TYPE(pg, indx) (*P_ENTRY(pg, indx))
/*
* The first and second types are H_KEYDATA and H_DUPLICATE, represented
* by the HKEYDATA structure:
*
* +-----------------------------------+
* | type | key/data ... |
* +-----------------------------------+
*
* For duplicates, the data field encodes duplicate elements in the data
* field:
*
* +---------------------------------------------------------------+
* | type | len1 | element1 | len1 | len2 | element2 | len2 |
* +---------------------------------------------------------------+
*
* Thus, by keeping track of the offset in the element, we can do both
* backward and forward traversal.
*/
typedef struct _hkeydata {
u_int8_t type; /* 00: Page type. */
u_int8_t data[1]; /* Variable length key/data item. */
} HKEYDATA;
#define HKEYDATA_DATA(p) (((u_int8_t *)p) + SSZA(HKEYDATA, data))
/*
* The length of any HKEYDATA item. Note that indx is an element index,
* not a PAIR index.
*/
#define LEN_HITEM(pg, pgsize, indx) \
(((indx) == 0 ? pgsize : pg->inp[indx - 1]) - pg->inp[indx])
#define LEN_HKEYDATA(pg, psize, indx) \
(((indx) == 0 ? psize : pg->inp[indx - 1]) - \
pg->inp[indx] - HKEYDATA_SIZE(0))
/*
* Page space required to add a new HKEYDATA item to the page, with and
* without the index value.
*/
#define HKEYDATA_SIZE(len) \
((len) + SSZA(HKEYDATA, data))
#define HKEYDATA_PSIZE(len) \
(HKEYDATA_SIZE(len) + sizeof(db_indx_t))
/* Put a HKEYDATA item at the location referenced by a page entry. */
#define PUT_HKEYDATA(pe, kd, len, type) { \
((HKEYDATA *)pe)->type = type; \
memcpy((u_int8_t *)pe + sizeof(u_int8_t), kd, len); \
}
/*
* Macros the describe the page layout in terms of key-data pairs.
* The use of "pindex" indicates that the argument is the index
* expressed in pairs instead of individual elements.
*/
#define H_NUMPAIRS(pg) (NUM_ENT(pg) / 2)
#define H_KEYINDEX(pindx) (2 * (pindx))
#define H_DATAINDEX(pindx) ((2 * (pindx)) + 1)
#define H_PAIRKEY(pg, pindx) P_ENTRY(pg, H_KEYINDEX(pindx))
#define H_PAIRDATA(pg, pindx) P_ENTRY(pg, H_DATAINDEX(pindx))
#define H_PAIRSIZE(pg, psize, pindx) \
(LEN_HITEM(pg, psize, H_KEYINDEX(pindx)) + \
LEN_HITEM(pg, psize, H_DATAINDEX(pindx)))
#define LEN_HDATA(p, psize, pindx) LEN_HKEYDATA(p, psize, H_DATAINDEX(pindx))
#define LEN_HKEY(p, psize, pindx) LEN_HKEYDATA(p, psize, H_KEYINDEX(pindx))
/*
* The third type is the H_OFFPAGE, represented by the HOFFPAGE structure:
*
* +-----------------------------------+
* | type | pgno_t | total len |
* +-----------------------------------+
*/
typedef struct _hoffpage {
u_int8_t type; /* 00: Page type and delete flag. */
u_int8_t unused[3]; /* 01-03: Padding, unused. */
db_pgno_t pgno; /* 04-07: Offpage page number. */
u_int32_t tlen; /* 08-11: Total length of item. */
} HOFFPAGE;
#define HOFFPAGE_PGNO(p) (((u_int8_t *)p) + SSZ(HOFFPAGE, pgno))
#define HOFFPAGE_TLEN(p) (((u_int8_t *)p) + SSZ(HOFFPAGE, tlen))
/*
* Page space required to add a new HOFFPAGE item to the page, with and
* without the index value.
*/
#define HOFFPAGE_SIZE (sizeof(HOFFPAGE))
#define HOFFPAGE_PSIZE (HOFFPAGE_SIZE + sizeof(db_indx_t))
/*
* The fourth type is H_OFFDUP represented by the HOFFDUP structure:
*
* +-----------------------+
* | type | pgno_t |
* +-----------------------+
*/
typedef struct _hoffdup {
u_int8_t type; /* 00: Page type and delete flag. */
u_int8_t unused[3]; /* 01-03: Padding, unused. */
db_pgno_t pgno; /* 04-07: Offpage page number. */
} HOFFDUP;
#define HOFFDUP_PGNO(p) (((u_int8_t *)p) + SSZ(HOFFDUP, pgno))
/*
* Page space required to add a new HOFFDUP item to the page, with and
* without the index value.
*/
#define HOFFDUP_SIZE (sizeof(HOFFDUP))
#define HOFFDUP_PSIZE (HOFFDUP_SIZE + sizeof(db_indx_t))
/************************************************************************
BTREE PAGE LAYOUT
************************************************************************/
/* Each index references a group of bytes on the page. */
#define B_KEYDATA 1 /* Key/data item. */
#define B_DUPLICATE 2 /* Duplicate key/data item. */
#define B_OVERFLOW 3 /* Overflow key/data item. */
/*
* We have to store a deleted entry flag in the page. The reason is complex,
* but the simple version is that we can't delete on-page items referenced by
* a cursor -- the return order of subsequent insertions might be wrong. The
* delete flag is an overload of the top bit of the type byte.
*/
#define B_DELETE (0x80)
#define B_DCLR(t) (t) &= ~B_DELETE
#define B_DSET(t) (t) |= B_DELETE
#define B_DISSET(t) ((t) & B_DELETE)
#define B_TYPE(t) ((t) & ~B_DELETE)
#define B_TSET(t, type, deleted) { \
(t) = (type); \
if (deleted) \
B_DSET(t); \
}
/*
* The first type is B_KEYDATA, represented by the BKEYDATA structure:
*
* +-----------------------------------+
* | length | type | key/data |
* +-----------------------------------+
*/
typedef struct _bkeydata {
db_indx_t len; /* 00-01: Key/data item length. */
u_int8_t type; /* 02: Page type AND DELETE FLAG. */
u_int8_t data[1]; /* Variable length key/data item. */
} BKEYDATA;
/* Get a BKEYDATA item for a specific index. */
#define GET_BKEYDATA(pg, indx) \
((BKEYDATA *)P_ENTRY(pg, indx))
/*
* Page space required to add a new BKEYDATA item to the page, with and
* without the index value.
*/
#define BKEYDATA_SIZE(len) \
ALIGN((len) + SSZA(BKEYDATA, data), 4)
#define BKEYDATA_PSIZE(len) \
(BKEYDATA_SIZE(len) + sizeof(db_indx_t))
/*
* The second and third types are B_DUPLICATE and B_OVERFLOW, represented
* by the BOVERFLOW structure:
*
* +-----------------------------------+
* | total len | type | unused |
* +-----------------------------------+
* | nxt: page | nxt: off | nxt: len |
* +-----------------------------------+
*/
typedef struct _boverflow {
db_indx_t unused1; /* 00-01: Padding, unused. */
u_int8_t type; /* 02: Page type AND DELETE FLAG. */
u_int8_t unused2; /* 03: Padding, unused. */
db_pgno_t pgno; /* 04-07: Next page number. */
u_int32_t tlen; /* 08-11: Total length of item. */
} BOVERFLOW;
/* Get a BOVERFLOW item for a specific index. */
#define GET_BOVERFLOW(pg, indx) \
((BOVERFLOW *)P_ENTRY(pg, indx))
/*
* Page space required to add a new BOVERFLOW item to the page, with and
* without the index value.
*/
#define BOVERFLOW_SIZE \
ALIGN(sizeof(BOVERFLOW), 4)
#define BOVERFLOW_PSIZE \
(BOVERFLOW_SIZE + sizeof(db_indx_t))
/*
* Btree leaf and hash page layouts group indices in sets of two, one
* for the key and one for the data. Everything else does it in sets
* of one to save space. I use the following macros so that it's real
* obvious what's going on...
*/
#define O_INDX 1
#define P_INDX 2
/************************************************************************
BTREE INTERNAL PAGE LAYOUT
************************************************************************/
/*
* Btree internal entry.
*
* +-----------------------------------+
* | leaf pgno | type | data ... |
* +-----------------------------------+
*/
typedef struct _binternal {
db_indx_t len; /* 00-01: Key/data item length. */
u_int8_t type; /* 02: Page type AND DELETE FLAG. */
u_int8_t unused; /* 03: Padding, unused. */
db_pgno_t pgno; /* 04-07: Page number of referenced page. */
db_recno_t nrecs; /* 08-11: Subtree record count. */
u_int8_t data[1]; /* Variable length key item. */
} BINTERNAL;
/* Get a BINTERNAL item for a specific index. */
#define GET_BINTERNAL(pg, indx) \
((BINTERNAL *)P_ENTRY(pg, indx))
/*
* Page space required to add a new BINTERNAL item to the page, with and
* without the index value.
*/
#define BINTERNAL_SIZE(len) \
ALIGN((len) + SSZA(BINTERNAL, data), 4)
#define BINTERNAL_PSIZE(len) \
(BINTERNAL_SIZE(len) + sizeof(db_indx_t))
/************************************************************************
RECNO INTERNAL PAGE LAYOUT
************************************************************************/
/*
* The recno internal entry.
*
* +-----------------------+
* | leaf pgno | # of recs |
* +-----------------------+
*
* XXX
* Why not fold this into the db_indx_t structure, it's fixed length.
*/
typedef struct _rinternal {
db_pgno_t pgno; /* 00-03: Page number of referenced page. */
db_recno_t nrecs; /* 04-07: Subtree record count. */
} RINTERNAL;
/* Get a RINTERNAL item for a specific index. */
#define GET_RINTERNAL(pg, indx) \
((RINTERNAL *)P_ENTRY(pg, indx))
/*
* Page space required to add a new RINTERNAL item to the page, with and
* without the index value.
*/
#define RINTERNAL_SIZE \
ALIGN(sizeof(RINTERNAL), 4)
#define RINTERNAL_PSIZE \
(RINTERNAL_SIZE + sizeof(db_indx_t))
#endif /* _DB_PAGE_H_ */
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