/*** 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 1282 2008-11-13 09:31:33Z LarsPson $**** 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\000"** 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 3 bytes. Such small cells will be** exceedingly rare, but they are possible.*/#define MX_CELL(pBt) ((pBt->pageSize-8)/3)/* 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 */#endif};/*** 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 */ int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */ void *pArg; /* First arg to xCompare() */ 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 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 sqlite3_btree_trace is** enabled.*/#if SQLITE_TEST# define TRACE(X) if( sqlite3_btree_trace ){ 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_TESTu8 *sqlite3BtreeFindCell(MemPage *pPage, int iCell);#endifint sqlite3BtreeRestoreOrClearCursorPosition(BtCursor *pCur);void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur);void sqlite3BtreeReleaseTempCursor(BtCursor *pCur);int sqlite3BtreeIsRootPage(MemPage *pPage);void sqlite3BtreeMoveToParent(BtCursor *pCur);