btreeInt.h
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- /*
- ** 2004 April 6
- **
- ** The author disclaims copyright to this source code. In place of
- ** a legal notice, here is a blessing:
- **
- ** May you do good and not evil.
- ** May you find forgiveness for yourself and forgive others.
- ** May you share freely, never taking more than you give.
- **
- *************************************************************************
- ** $Id: btreeInt.h,v 1.20 2008/03/29 16:01:04 drh Exp $
- **
- ** This file implements a external (disk-based) database using BTrees.
- ** For a detailed discussion of BTrees, refer to
- **
- ** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
- ** "Sorting And Searching", pages 473-480. Addison-Wesley
- ** Publishing Company, Reading, Massachusetts.
- **
- ** The basic idea is that each page of the file contains N database
- ** entries and N+1 pointers to subpages.
- **
- ** ----------------------------------------------------------------
- ** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
- ** ----------------------------------------------------------------
- **
- ** All of the keys on the page that Ptr(0) points to have values less
- ** than Key(0). All of the keys on page Ptr(1) and its subpages have
- ** values greater than Key(0) and less than Key(1). All of the keys
- ** on Ptr(N) and its subpages have values greater than Key(N-1). And
- ** so forth.
- **
- ** Finding a particular key requires reading O(log(M)) pages from the
- ** disk where M is the number of entries in the tree.
- **
- ** In this implementation, a single file can hold one or more separate
- ** BTrees. Each BTree is identified by the index of its root page. The
- ** key and data for any entry are combined to form the "payload". A
- ** fixed amount of payload can be carried directly on the database
- ** page. If the payload is larger than the preset amount then surplus
- ** bytes are stored on overflow pages. The payload for an entry
- ** and the preceding pointer are combined to form a "Cell". Each
- ** page has a small header which contains the Ptr(N) pointer and other
- ** information such as the size of key and data.
- **
- ** FORMAT DETAILS
- **
- ** The file is divided into pages. The first page is called page 1,
- ** the second is page 2, and so forth. A page number of zero indicates
- ** "no such page". The page size can be anything between 512 and 65536.
- ** Each page can be either a btree page, a freelist page or an overflow
- ** page.
- **
- ** The first page is always a btree page. The first 100 bytes of the first
- ** page contain a special header (the "file header") that describes the file.
- ** The format of the file header is as follows:
- **
- ** OFFSET SIZE DESCRIPTION
- ** 0 16 Header string: "SQLite format 3 00"
- ** 16 2 Page size in bytes.
- ** 18 1 File format write version
- ** 19 1 File format read version
- ** 20 1 Bytes of unused space at the end of each page
- ** 21 1 Max embedded payload fraction
- ** 22 1 Min embedded payload fraction
- ** 23 1 Min leaf payload fraction
- ** 24 4 File change counter
- ** 28 4 Reserved for future use
- ** 32 4 First freelist page
- ** 36 4 Number of freelist pages in the file
- ** 40 60 15 4-byte meta values passed to higher layers
- **
- ** All of the integer values are big-endian (most significant byte first).
- **
- ** The file change counter is incremented when the database is changed
- ** This counter allows other processes to know when the file has changed
- ** and thus when they need to flush their cache.
- **
- ** The max embedded payload fraction is the amount of the total usable
- ** space in a page that can be consumed by a single cell for standard
- ** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default
- ** is to limit the maximum cell size so that at least 4 cells will fit
- ** on one page. Thus the default max embedded payload fraction is 64.
- **
- ** If the payload for a cell is larger than the max payload, then extra
- ** payload is spilled to overflow pages. Once an overflow page is allocated,
- ** as many bytes as possible are moved into the overflow pages without letting
- ** the cell size drop below the min embedded payload fraction.
- **
- ** The min leaf payload fraction is like the min embedded payload fraction
- ** except that it applies to leaf nodes in a LEAFDATA tree. The maximum
- ** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
- ** not specified in the header.
- **
- ** Each btree pages is divided into three sections: The header, the
- ** cell pointer array, and the cell content area. Page 1 also has a 100-byte
- ** file header that occurs before the page header.
- **
- ** |----------------|
- ** | file header | 100 bytes. Page 1 only.
- ** |----------------|
- ** | page header | 8 bytes for leaves. 12 bytes for interior nodes
- ** |----------------|
- ** | cell pointer | | 2 bytes per cell. Sorted order.
- ** | array | | Grows downward
- ** | | v
- ** |----------------|
- ** | unallocated |
- ** | space |
- ** |----------------| ^ Grows upwards
- ** | cell content | | Arbitrary order interspersed with freeblocks.
- ** | area | | and free space fragments.
- ** |----------------|
- **
- ** The page headers looks like this:
- **
- ** OFFSET SIZE DESCRIPTION
- ** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
- ** 1 2 byte offset to the first freeblock
- ** 3 2 number of cells on this page
- ** 5 2 first byte of the cell content area
- ** 7 1 number of fragmented free bytes
- ** 8 4 Right child (the Ptr(N) value). Omitted on leaves.
- **
- ** The flags define the format of this btree page. The leaf flag means that
- ** this page has no children. The zerodata flag means that this page carries
- ** only keys and no data. The intkey flag means that the key is a integer
- ** which is stored in the key size entry of the cell header rather than in
- ** the payload area.
- **
- ** The cell pointer array begins on the first byte after the page header.
- ** The cell pointer array contains zero or more 2-byte numbers which are
- ** offsets from the beginning of the page to the cell content in the cell
- ** content area. The cell pointers occur in sorted order. The system strives
- ** to keep free space after the last cell pointer so that new cells can
- ** be easily added without having to defragment the page.
- **
- ** Cell content is stored at the very end of the page and grows toward the
- ** beginning of the page.
- **
- ** Unused space within the cell content area is collected into a linked list of
- ** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset
- ** to the first freeblock is given in the header. Freeblocks occur in
- ** increasing order. Because a freeblock must be at least 4 bytes in size,
- ** any group of 3 or fewer unused bytes in the cell content area cannot
- ** exist on the freeblock chain. A group of 3 or fewer free bytes is called
- ** a fragment. The total number of bytes in all fragments is recorded.
- ** in the page header at offset 7.
- **
- ** SIZE DESCRIPTION
- ** 2 Byte offset of the next freeblock
- ** 2 Bytes in this freeblock
- **
- ** Cells are of variable length. Cells are stored in the cell content area at
- ** the end of the page. Pointers to the cells are in the cell pointer array
- ** that immediately follows the page header. Cells is not necessarily
- ** contiguous or in order, but cell pointers are contiguous and in order.
- **
- ** Cell content makes use of variable length integers. A variable
- ** length integer is 1 to 9 bytes where the lower 7 bits of each
- ** byte are used. The integer consists of all bytes that have bit 8 set and
- ** the first byte with bit 8 clear. The most significant byte of the integer
- ** appears first. A variable-length integer may not be more than 9 bytes long.
- ** As a special case, all 8 bytes of the 9th byte are used as data. This
- ** allows a 64-bit integer to be encoded in 9 bytes.
- **
- ** 0x00 becomes 0x00000000
- ** 0x7f becomes 0x0000007f
- ** 0x81 0x00 becomes 0x00000080
- ** 0x82 0x00 becomes 0x00000100
- ** 0x80 0x7f becomes 0x0000007f
- ** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678
- ** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081
- **
- ** Variable length integers are used for rowids and to hold the number of
- ** bytes of key and data in a btree cell.
- **
- ** The content of a cell looks like this:
- **
- ** SIZE DESCRIPTION
- ** 4 Page number of the left child. Omitted if leaf flag is set.
- ** var Number of bytes of data. Omitted if the zerodata flag is set.
- ** var Number of bytes of key. Or the key itself if intkey flag is set.
- ** * Payload
- ** 4 First page of the overflow chain. Omitted if no overflow
- **
- ** Overflow pages form a linked list. Each page except the last is completely
- ** filled with data (pagesize - 4 bytes). The last page can have as little
- ** as 1 byte of data.
- **
- ** SIZE DESCRIPTION
- ** 4 Page number of next overflow page
- ** * Data
- **
- ** Freelist pages come in two subtypes: trunk pages and leaf pages. The
- ** file header points to the first in a linked list of trunk page. Each trunk
- ** page points to multiple leaf pages. The content of a leaf page is
- ** unspecified. A trunk page looks like this:
- **
- ** SIZE DESCRIPTION
- ** 4 Page number of next trunk page
- ** 4 Number of leaf pointers on this page
- ** * zero or more pages numbers of leaves
- */
- #include "sqliteInt.h"
- #include "pager.h"
- #include "btree.h"
- #include "os.h"
- #include <assert.h>
- /* Round up a number to the next larger multiple of 8. This is used
- ** to force 8-byte alignment on 64-bit architectures.
- */
- #define ROUND8(x) ((x+7)&~7)
- /* The following value is the maximum cell size assuming a maximum page
- ** size give above.
- */
- #define MX_CELL_SIZE(pBt) (pBt->pageSize-8)
- /* The maximum number of cells on a single page of the database. This
- ** assumes a minimum cell size of 6 bytes (4 bytes for the cell itself
- ** plus 2 bytes for the index to the cell in the page header). Such
- ** small cells will be rare, but they are possible.
- */
- #define MX_CELL(pBt) ((pBt->pageSize-8)/6)
- /* Forward declarations */
- typedef struct MemPage MemPage;
- typedef struct BtLock BtLock;
- /*
- ** This is a magic string that appears at the beginning of every
- ** SQLite database in order to identify the file as a real database.
- **
- ** You can change this value at compile-time by specifying a
- ** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The
- ** header must be exactly 16 bytes including the zero-terminator so
- ** the string itself should be 15 characters long. If you change
- ** the header, then your custom library will not be able to read
- ** databases generated by the standard tools and the standard tools
- ** will not be able to read databases created by your custom library.
- */
- #ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
- # define SQLITE_FILE_HEADER "SQLite format 3"
- #endif
- /*
- ** Page type flags. An ORed combination of these flags appear as the
- ** first byte of on-disk image of every BTree page.
- */
- #define PTF_INTKEY 0x01
- #define PTF_ZERODATA 0x02
- #define PTF_LEAFDATA 0x04
- #define PTF_LEAF 0x08
- /*
- ** As each page of the file is loaded into memory, an instance of the following
- ** structure is appended and initialized to zero. This structure stores
- ** information about the page that is decoded from the raw file page.
- **
- ** The pParent field points back to the parent page. This allows us to
- ** walk up the BTree from any leaf to the root. Care must be taken to
- ** unref() the parent page pointer when this page is no longer referenced.
- ** The pageDestructor() routine handles that chore.
- **
- ** Access to all fields of this structure is controlled by the mutex
- ** stored in MemPage.pBt->mutex.
- */
- struct MemPage {
- u8 isInit; /* True if previously initialized. MUST BE FIRST! */
- u8 idxShift; /* True if Cell indices have changed */
- u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
- u8 intKey; /* True if intkey flag is set */
- u8 leaf; /* True if leaf flag is set */
- u8 zeroData; /* True if table stores keys only */
- u8 leafData; /* True if tables stores data on leaves only */
- u8 hasData; /* True if this page stores data */
- u8 hdrOffset; /* 100 for page 1. 0 otherwise */
- u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
- u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
- u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */
- u16 cellOffset; /* Index in aData of first cell pointer */
- u16 idxParent; /* Index in parent of this node */
- u16 nFree; /* Number of free bytes on the page */
- u16 nCell; /* Number of cells on this page, local and ovfl */
- struct _OvflCell { /* Cells that will not fit on aData[] */
- u8 *pCell; /* Pointers to the body of the overflow cell */
- u16 idx; /* Insert this cell before idx-th non-overflow cell */
- } aOvfl[5];
- BtShared *pBt; /* Pointer to BtShared that this page is part of */
- u8 *aData; /* Pointer to disk image of the page data */
- DbPage *pDbPage; /* Pager page handle */
- Pgno pgno; /* Page number for this page */
- MemPage *pParent; /* The parent of this page. NULL for root */
- };
- /*
- ** The in-memory image of a disk page has the auxiliary information appended
- ** to the end. EXTRA_SIZE is the number of bytes of space needed to hold
- ** that extra information.
- */
- #define EXTRA_SIZE sizeof(MemPage)
- /* A Btree handle
- **
- ** A database connection contains a pointer to an instance of
- ** this object for every database file that it has open. This structure
- ** is opaque to the database connection. The database connection cannot
- ** see the internals of this structure and only deals with pointers to
- ** this structure.
- **
- ** For some database files, the same underlying database cache might be
- ** shared between multiple connections. In that case, each contection
- ** has it own pointer to this object. But each instance of this object
- ** points to the same BtShared object. The database cache and the
- ** schema associated with the database file are all contained within
- ** the BtShared object.
- **
- ** All fields in this structure are accessed under sqlite3.mutex.
- ** The pBt pointer itself may not be changed while there exists cursors
- ** in the referenced BtShared that point back to this Btree since those
- ** cursors have to do go through this Btree to find their BtShared and
- ** they often do so without holding sqlite3.mutex.
- */
- struct Btree {
- sqlite3 *db; /* The database connection holding this btree */
- BtShared *pBt; /* Sharable content of this btree */
- u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
- u8 sharable; /* True if we can share pBt with another db */
- u8 locked; /* True if db currently has pBt locked */
- int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
- Btree *pNext; /* List of other sharable Btrees from the same db */
- Btree *pPrev; /* Back pointer of the same list */
- };
- /*
- ** Btree.inTrans may take one of the following values.
- **
- ** If the shared-data extension is enabled, there may be multiple users
- ** of the Btree structure. At most one of these may open a write transaction,
- ** but any number may have active read transactions.
- */
- #define TRANS_NONE 0
- #define TRANS_READ 1
- #define TRANS_WRITE 2
- /*
- ** An instance of this object represents a single database file.
- **
- ** A single database file can be in use as the same time by two
- ** or more database connections. When two or more connections are
- ** sharing the same database file, each connection has it own
- ** private Btree object for the file and each of those Btrees points
- ** to this one BtShared object. BtShared.nRef is the number of
- ** connections currently sharing this database file.
- **
- ** Fields in this structure are accessed under the BtShared.mutex
- ** mutex, except for nRef and pNext which are accessed under the
- ** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field
- ** may not be modified once it is initially set as long as nRef>0.
- ** The pSchema field may be set once under BtShared.mutex and
- ** thereafter is unchanged as long as nRef>0.
- */
- struct BtShared {
- Pager *pPager; /* The page cache */
- sqlite3 *db; /* Database connection currently using this Btree */
- BtCursor *pCursor; /* A list of all open cursors */
- MemPage *pPage1; /* First page of the database */
- u8 inStmt; /* True if we are in a statement subtransaction */
- u8 readOnly; /* True if the underlying file is readonly */
- u8 maxEmbedFrac; /* Maximum payload as % of total page size */
- u8 minEmbedFrac; /* Minimum payload as % of total page size */
- u8 minLeafFrac; /* Minimum leaf payload as % of total page size */
- u8 pageSizeFixed; /* True if the page size can no longer be changed */
- #ifndef SQLITE_OMIT_AUTOVACUUM
- u8 autoVacuum; /* True if auto-vacuum is enabled */
- u8 incrVacuum; /* True if incr-vacuum is enabled */
- Pgno nTrunc; /* Non-zero if the db will be truncated (incr vacuum) */
- #endif
- u16 pageSize; /* Total number of bytes on a page */
- u16 usableSize; /* Number of usable bytes on each page */
- int maxLocal; /* Maximum local payload in non-LEAFDATA tables */
- int minLocal; /* Minimum local payload in non-LEAFDATA tables */
- int maxLeaf; /* Maximum local payload in a LEAFDATA table */
- int minLeaf; /* Minimum local payload in a LEAFDATA table */
- u8 inTransaction; /* Transaction state */
- int nTransaction; /* Number of open transactions (read + write) */
- void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */
- void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */
- sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */
- BusyHandler busyHdr; /* The busy handler for this btree */
- #ifndef SQLITE_OMIT_SHARED_CACHE
- int nRef; /* Number of references to this structure */
- BtShared *pNext; /* Next on a list of sharable BtShared structs */
- BtLock *pLock; /* List of locks held on this shared-btree struct */
- Btree *pExclusive; /* Btree with an EXCLUSIVE lock on the whole db */
- #endif
- u8 *pTmpSpace; /* BtShared.pageSize bytes of space for tmp use */
- };
- /*
- ** An instance of the following structure is used to hold information
- ** about a cell. The parseCellPtr() function fills in this structure
- ** based on information extract from the raw disk page.
- */
- typedef struct CellInfo CellInfo;
- struct CellInfo {
- u8 *pCell; /* Pointer to the start of cell content */
- i64 nKey; /* The key for INTKEY tables, or number of bytes in key */
- u32 nData; /* Number of bytes of data */
- u32 nPayload; /* Total amount of payload */
- u16 nHeader; /* Size of the cell content header in bytes */
- u16 nLocal; /* Amount of payload held locally */
- u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */
- u16 nSize; /* Size of the cell content on the main b-tree page */
- };
- /*
- ** A cursor is a pointer to a particular entry within a particular
- ** b-tree within a database file.
- **
- ** The entry is identified by its MemPage and the index in
- ** MemPage.aCell[] of the entry.
- **
- ** When a single database file can shared by two more database connections,
- ** but cursors cannot be shared. Each cursor is associated with a
- ** particular database connection identified BtCursor.pBtree.db.
- **
- ** Fields in this structure are accessed under the BtShared.mutex
- ** found at self->pBt->mutex.
- */
- struct BtCursor {
- Btree *pBtree; /* The Btree to which this cursor belongs */
- BtShared *pBt; /* The BtShared this cursor points to */
- BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */
- struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
- Pgno pgnoRoot; /* The root page of this tree */
- MemPage *pPage; /* Page that contains the entry */
- int idx; /* Index of the entry in pPage->aCell[] */
- CellInfo info; /* A parse of the cell we are pointing at */
- u8 wrFlag; /* True if writable */
- u8 atLast; /* Cursor pointing to the last entry */
- u8 validNKey; /* True if info.nKey is valid */
- u8 eState; /* One of the CURSOR_XXX constants (see below) */
- void *pKey; /* Saved key that was cursor's last known position */
- i64 nKey; /* Size of pKey, or last integer key */
- int skip; /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */
- #ifndef SQLITE_OMIT_INCRBLOB
- u8 isIncrblobHandle; /* True if this cursor is an incr. io handle */
- Pgno *aOverflow; /* Cache of overflow page locations */
- #endif
- };
- /*
- ** Potential values for BtCursor.eState.
- **
- ** CURSOR_VALID:
- ** Cursor points to a valid entry. getPayload() etc. may be called.
- **
- ** CURSOR_INVALID:
- ** Cursor does not point to a valid entry. This can happen (for example)
- ** because the table is empty or because BtreeCursorFirst() has not been
- ** called.
- **
- ** CURSOR_REQUIRESEEK:
- ** The table that this cursor was opened on still exists, but has been
- ** modified since the cursor was last used. The cursor position is saved
- ** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in
- ** this state, restoreOrClearCursorPosition() can be called to attempt to
- ** seek the cursor to the saved position.
- **
- ** CURSOR_FAULT:
- ** A unrecoverable error (an I/O error or a malloc failure) has occurred
- ** on a different connection that shares the BtShared cache with this
- ** cursor. The error has left the cache in an inconsistent state.
- ** Do nothing else with this cursor. Any attempt to use the cursor
- ** should return the error code stored in BtCursor.skip
- */
- #define CURSOR_INVALID 0
- #define CURSOR_VALID 1
- #define CURSOR_REQUIRESEEK 2
- #define CURSOR_FAULT 3
- /*
- ** The TRACE macro will print high-level status information about the
- ** btree operation when the global variable sqlite3BtreeTrace is
- ** enabled.
- */
- #if SQLITE_TEST
- # define TRACE(X) if( sqlite3BtreeTrace ){ printf X; fflush(stdout); }
- #else
- # define TRACE(X)
- #endif
- /*
- ** Routines to read and write variable-length integers. These used to
- ** be defined locally, but now we use the varint routines in the util.c
- ** file.
- */
- #define getVarint sqlite3GetVarint
- #define getVarint32(A,B) ((*B=*(A))<=0x7f?1:sqlite3GetVarint32(A,B))
- #define putVarint sqlite3PutVarint
- /* The database page the PENDING_BYTE occupies. This page is never used.
- ** TODO: This macro is very similary to PAGER_MJ_PGNO() in pager.c. They
- ** should possibly be consolidated (presumably in pager.h).
- **
- ** If disk I/O is omitted (meaning that the database is stored purely
- ** in memory) then there is no pending byte.
- */
- #ifdef SQLITE_OMIT_DISKIO
- # define PENDING_BYTE_PAGE(pBt) 0x7fffffff
- #else
- # define PENDING_BYTE_PAGE(pBt) ((PENDING_BYTE/(pBt)->pageSize)+1)
- #endif
- /*
- ** A linked list of the following structures is stored at BtShared.pLock.
- ** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor
- ** is opened on the table with root page BtShared.iTable. Locks are removed
- ** from this list when a transaction is committed or rolled back, or when
- ** a btree handle is closed.
- */
- struct BtLock {
- Btree *pBtree; /* Btree handle holding this lock */
- Pgno iTable; /* Root page of table */
- u8 eLock; /* READ_LOCK or WRITE_LOCK */
- BtLock *pNext; /* Next in BtShared.pLock list */
- };
- /* Candidate values for BtLock.eLock */
- #define READ_LOCK 1
- #define WRITE_LOCK 2
- /*
- ** These macros define the location of the pointer-map entry for a
- ** database page. The first argument to each is the number of usable
- ** bytes on each page of the database (often 1024). The second is the
- ** page number to look up in the pointer map.
- **
- ** PTRMAP_PAGENO returns the database page number of the pointer-map
- ** page that stores the required pointer. PTRMAP_PTROFFSET returns
- ** the offset of the requested map entry.
- **
- ** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
- ** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
- ** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
- ** this test.
- */
- #define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
- #define PTRMAP_PTROFFSET(pBt, pgno) (5*(pgno-ptrmapPageno(pBt, pgno)-1))
- #define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
- /*
- ** The pointer map is a lookup table that identifies the parent page for
- ** each child page in the database file. The parent page is the page that
- ** contains a pointer to the child. Every page in the database contains
- ** 0 or 1 parent pages. (In this context 'database page' refers
- ** to any page that is not part of the pointer map itself.) Each pointer map
- ** entry consists of a single byte 'type' and a 4 byte parent page number.
- ** The PTRMAP_XXX identifiers below are the valid types.
- **
- ** The purpose of the pointer map is to facility moving pages from one
- ** position in the file to another as part of autovacuum. When a page
- ** is moved, the pointer in its parent must be updated to point to the
- ** new location. The pointer map is used to locate the parent page quickly.
- **
- ** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
- ** used in this case.
- **
- ** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number
- ** is not used in this case.
- **
- ** PTRMAP_OVERFLOW1: The database page is the first page in a list of
- ** overflow pages. The page number identifies the page that
- ** contains the cell with a pointer to this overflow page.
- **
- ** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
- ** overflow pages. The page-number identifies the previous
- ** page in the overflow page list.
- **
- ** PTRMAP_BTREE: The database page is a non-root btree page. The page number
- ** identifies the parent page in the btree.
- */
- #define PTRMAP_ROOTPAGE 1
- #define PTRMAP_FREEPAGE 2
- #define PTRMAP_OVERFLOW1 3
- #define PTRMAP_OVERFLOW2 4
- #define PTRMAP_BTREE 5
- /* A bunch of assert() statements to check the transaction state variables
- ** of handle p (type Btree*) are internally consistent.
- */
- #define btreeIntegrity(p)
- assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 );
- assert( p->pBt->inTransaction>=p->inTrans );
- /*
- ** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
- ** if the database supports auto-vacuum or not. Because it is used
- ** within an expression that is an argument to another macro
- ** (sqliteMallocRaw), it is not possible to use conditional compilation.
- ** So, this macro is defined instead.
- */
- #ifndef SQLITE_OMIT_AUTOVACUUM
- #define ISAUTOVACUUM (pBt->autoVacuum)
- #else
- #define ISAUTOVACUUM 0
- #endif
- /*
- ** This structure is passed around through all the sanity checking routines
- ** in order to keep track of some global state information.
- */
- typedef struct IntegrityCk IntegrityCk;
- struct IntegrityCk {
- BtShared *pBt; /* The tree being checked out */
- Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */
- int nPage; /* Number of pages in the database */
- int *anRef; /* Number of times each page is referenced */
- int mxErr; /* Stop accumulating errors when this reaches zero */
- char *zErrMsg; /* An error message. NULL if no errors seen. */
- int nErr; /* Number of messages written to zErrMsg so far */
- };
- /*
- ** Read or write a two- and four-byte big-endian integer values.
- */
- #define get2byte(x) ((x)[0]<<8 | (x)[1])
- #define put2byte(p,v) ((p)[0] = (v)>>8, (p)[1] = (v))
- #define get4byte sqlite3Get4byte
- #define put4byte sqlite3Put4byte
- /*
- ** Internal routines that should be accessed by the btree layer only.
- */
- int sqlite3BtreeGetPage(BtShared*, Pgno, MemPage**, int);
- int sqlite3BtreeInitPage(MemPage *pPage, MemPage *pParent);
- void sqlite3BtreeParseCellPtr(MemPage*, u8*, CellInfo*);
- void sqlite3BtreeParseCell(MemPage*, int, CellInfo*);
- #ifdef SQLITE_TEST
- u8 *sqlite3BtreeFindCell(MemPage *pPage, int iCell);
- #endif
- int sqlite3BtreeRestoreOrClearCursorPosition(BtCursor *pCur);
- void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur);
- void sqlite3BtreeReleaseTempCursor(BtCursor *pCur);
- int sqlite3BtreeIsRootPage(MemPage *pPage);
- void sqlite3BtreeMoveToParent(BtCursor *pCur);