/*
** 2001 September 15
**
** 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: btree.c,v 1.62 2002/06/06 23:16:05 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) | Ptr(N+1) |
** ----------------------------------------------------------------
**
** 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+1) and its subpages have values greater than Key(N). 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". Up to
** MX_LOCAL_PAYLOAD bytes of payload can be carried directly on the
** database page. If the payload is larger than MX_LOCAL_PAYLOAD bytes
** 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+1) pointer.
**
** The first page of the file contains a magic string used to verify that
** the file really is a valid BTree database, a pointer to a list of unused
** pages in the file, and some meta information. The root of the first
** BTree begins on page 2 of the file. (Pages are numbered beginning with
** 1, not 0.) Thus a minimum database contains 2 pages.
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include <assert.h>
/*
** Forward declarations of structures used only in this file.
*/
typedef struct PageOne PageOne;
typedef struct MemPage MemPage;
typedef struct PageHdr PageHdr;
typedef struct Cell Cell;
typedef struct CellHdr CellHdr;
typedef struct FreeBlk FreeBlk;
typedef struct OverflowPage OverflowPage;
typedef struct FreelistInfo FreelistInfo;
/*
** All structures on a database page are aligned to 4-byte boundries.
** This routine rounds up a number of bytes to the next multiple of 4.
**
** This might need to change for computer architectures that require
** and 8-byte alignment boundry for structures.
*/
#define ROUNDUP(X) ((X+3) & ~3)
/*
** This is a magic string that appears at the beginning of every
** SQLite database in order to identify the file as a real database.
*/
static const char zMagicHeader[] =
"** This file contains an SQLite 2.1 database **";
#define MAGIC_SIZE (sizeof(zMagicHeader))
/*
** This is a magic integer also used to test the integrity of the database
** file. This integer is used in addition to the string above so that
** if the file is written on a little-endian architecture and read
** on a big-endian architectures (or vice versa) we can detect the
** problem.
**
** The number used was obtained at random and has no special
** significance other than the fact that it represents a different
** integer on little-endian and big-endian machines.
*/
#define MAGIC 0xdae37528
/*
** The first page of the database file contains a magic header string
** to identify the file as an SQLite database file. It also contains
** a pointer to the first free page of the file. Page 2 contains the
** root of the principle BTree. The file might contain other BTrees
** rooted on pages above 2.
**
** The first page also contains SQLITE_N_BTREE_META integers that
** can be used by higher-level routines.
**
** Remember that pages are numbered beginning with 1. (See pager.c
** for additional information.) Page 0 does not exist and a page
** number of 0 is used to mean "no such page".
*/
struct PageOne {
char zMagic[MAGIC_SIZE]; /* String that identifies the file as a database */
int iMagic; /* Integer to verify correct byte order */
Pgno freeList; /* First free page in a list of all free pages */
int nFree; /* Number of pages on the free list */
int aMeta[SQLITE_N_BTREE_META-1]; /* User defined integers */
};
/*
** Each database page has a header that is an instance of this
** structure.
**
** PageHdr.firstFree is 0 if there is no free space on this page.
** Otherwise, PageHdr.firstFree is the index in MemPage.u.aDisk[] of a
** FreeBlk structure that describes the first block of free space.
** All free space is defined by a linked list of FreeBlk structures.
**
** Data is stored in a linked list of Cell structures. PageHdr.firstCell
** is the index into MemPage.u.aDisk[] of the first cell on the page. The
** Cells are kept in sorted order.
**
** A Cell contains all information about a database entry and a pointer
** to a child page that contains other entries less than itself. In
** other words, the i-th Cell contains both Ptr(i) and Key(i). The
** right-most pointer of the page is contained in PageHdr.rightChild.
*/
struct PageHdr {
Pgno rightChild; /* Child page that comes after all cells on this page */
u16 firstCell; /* Index in MemPage.u.aDisk[] of the first cell */
u16 firstFree; /* Index in MemPage.u.aDisk[] of the first free block */
};
/*
** Entries on a page of the database are called "Cells". Each Cell
** has a header and data. This structure defines the header. The
** key and data (collectively the "payload") follow this header on
** the database page.
**
** A definition of the complete Cell structure is given below. The
** header for the cell must be defined first in order to do some
** of the sizing #defines that follow.
*/
struct CellHdr {
Pgno leftChild; /* Child page that comes before this cell */
u16 nKey; /* Number of bytes in the key */
u16 iNext; /* Index in MemPage.u.aDisk[] of next cell in sorted order */
u8 nKeyHi; /* Upper 8 bits of key size for keys larger than 64K bytes */
u8 nDataHi; /* Upper 8 bits of data size when the size is more than 64K */
u16 nData; /* Number of bytes of data */
};
/*
** The key and data size are split into a lower 16-bit segment and an
** upper 8-bit segment in order to pack them together into a smaller
** space. The following macros reassembly a key or data size back
** into an integer.
*/
#define NKEY(h) (h.nKey + h.nKeyHi*65536)
#define NDATA(h) (h.nData + h.nDataHi*65536)
/*
** The minimum size of a complete Cell. The Cell must contain a header
** and at least 4 bytes of payload.
*/
#define MIN_CELL_SIZE (sizeof(CellHdr)+4)
/*
** The maximum number of database entries that can be held in a single
** page of the database.
*/
#define MX_CELL ((SQLITE_PAGE_SIZE-sizeof(PageHdr))/MIN_CELL_SIZE)
/*
** The amount of usable space on a single page of the BTree. This is the
** page size minus the overhead of the page header.
*/
#define USABLE_SPACE (SQLITE_PAGE_SIZE - sizeof(PageHdr))
/*
** The maximum amount of payload (in bytes) that can be stored locally for
** a database entry. If the entry contains more data than this, the
** extra goes onto overflow pages.
**
** This number is chosen so that at least 4 cells will fit on every page.
*/
#define MX_LOCAL_PAYLOAD ((USABLE_SPACE/4-(sizeof(CellHdr)+sizeof(Pgno)))&~3)
/*
** Data on a database page is stored as a linked list of Cell structures.
** Both the key and the data are stored in aPayload[]. The key always comes
** first. The aPayload[] field grows as necessary to hold the key and data,
** up to a maximum of MX_LOCAL_PAYLOAD bytes. If the size of the key and
** data combined exceeds MX_LOCAL_PAYLOAD bytes, then Cell.ovfl is the
** page number of the first overflow page.
**
** Though this structure is fixed in size, the Cell on the database
** page varies in size. Every cell has a CellHdr and at least 4 bytes
** of payload space. Additional payload bytes (up to the maximum of
** MX_LOCAL_PAYLOAD) and the Cell.ovfl value are allocated only as
** needed.
*/
struct Cell {
CellHdr h; /* The cell header */
char aPayload[MX_LOCAL_PAYLOAD]; /* Key and data */
Pgno ovfl; /* The first overflow page */
};
/*
** Free space on a page is remembered using a linked list of the FreeBlk
** structures. Space on a database page is allocated in increments of
** at least 4 bytes and is always aligned to a 4-byte boundry. The
** linked list of FreeBlks is always kept in order by address.
*/
struct FreeBlk {
u16 iSize; /* Number of bytes in this block of free space */
u16 iNext; /* Index in MemPage.u.aDisk[] of the next free block */
};
/*
** The number of bytes of payload that will fit on a single overflow page.
*/
#define OVERFLOW_SIZE (SQLITE_PAGE_SIZE-sizeof(Pgno))
/*
** When the key and data for a single entry in the BTree will not fit in
** the MX_LOCAL_PAYLOAD bytes of space available on the database page,
** then all extra bytes are written to a linked list of overflow pages.
** Each overflow page is an instance of the following structure.
**
** Unused pages in the database are also represented by instances of
** the OverflowPage structure. The PageOne.freeList field is the
** page number of the first page in a linked list of unused database
** pages.
*/
struct OverflowPage {
Pgno iNext;
char aPayload[OVERFLOW_SIZE];
};
/*
** The PageOne.freeList field points to a linked list of overflow pages
** hold information about free pages. The aPayload section of each
** overflow page contains an instance of the following structure. The
** aFree[] array holds the page number of nFree unused pages in the disk
** file.
*/
struct FreelistInfo {
int nFree;
Pgno aFree[(OVERFLOW_SIZE-sizeof(int))/sizeof(Pgno)];
};
/*
** For every page in the database file, an instance of the following structure
** is stored in memory. The u.aDisk[] array contains the raw bits read from
** the disk. The rest is auxiliary information held in memory only. The
** auxiliary info is only valid for regular database pages - it is not
** used for overflow pages and pages on the freelist.
**
** Of particular interest in the auxiliary info is the apCell[] entry. Each
** apCell[] entry is a pointer to a Cell structure in u.aDisk[]. The cells are
** put in this array so that they can be accessed in constant time, rather
** than in linear time which would be needed if we had to walk the linked
** list on every access.
**
** Note that apCell[] contains enough space to hold up to two more Cells
** than can possibly fit on one page. In the steady state, every apCell[]
** points to memory inside u.aDisk[]. But in the middle of an insert
** operation, some apCell[] entries may temporarily point to data space
** outside of u.aDisk[]. This is a transient situation that is quickly
** resolved. But while it is happening, it is possible for a database
** page to hold as many as two more cells than it might otherwise hold.
** The extra two entries in apCell[] are an allowance for this situation.
**
** 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.
*/
struct MemPage {
union {
char aDisk[SQLITE_PAGE_SIZE]; /* Page data stored on disk */
PageHdr hdr; /* Overlay page header */
} u;
int isInit; /* True if auxiliary data is initialized */
MemPage *pParent; /* The parent of this page. NULL for root */
int nFree; /* Number of free bytes in u.aDisk[] */
int nCell; /* Number of entries on this page */
int isOverfull; /* Some apCell[] points outside u.aDisk[] */
Cell *apCell[MX_CELL+2]; /* All data entires in sorted order */
};
/*
** 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)-SQLITE_PAGE_SIZE)
/*
** Everything we need to know about an open database
*/
struct Btree {
Pager *pPager; /* The page cache */
BtCursor *pCursor; /* A list of all open cursors */
PageOne *page1; /* First page of the database */
u8 inTrans; /* True if a transaction is in progress */
u8 inCkpt; /* True if there is a checkpoint on the transaction */
u8 readOnly; /* True if the underlying file is readonly */
Hash locks; /* Key: root page number. Data: lock count */
};
typedef Btree Bt;
/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in
** MemPage.apCell[] of the entry.
*/
struct BtCursor {
Btree *pBt; /* The Btree to which this cursor belongs */
BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */
Pgno pgnoRoot; /* The root page of this tree */
MemPage *pPage; /* Page that contains the entry */
int idx; /* Index of the entry in pPage->apCell[] */
u8 wrFlag; /* True if writable */
u8 bSkipNext; /* sqliteBtreeNext() is no-op if true */
u8 iMatch; /* compare result from last sqliteBtreeMoveto() */
};
/*
** Compute the total number of bytes that a Cell needs on the main
** database page. The number returned includes the Cell header,
** local payload storage, and the pointer to overflow pages (if
** applicable). Additional space allocated on overflow pages
** is NOT included in the value returned from this routine.
*/
static int cellSize(Cell *pCell){
int n = NKEY(pCell->h) + NDATA(pCell->h);
if( n>MX_LOCAL_PAYLOAD ){
n = MX_LOCAL_PAYLOAD + sizeof(Pgno);
}else{
n = ROUNDUP(n);
}
n += sizeof(CellHdr);
return n;
}
/*
** Defragment the page given. All Cells are moved to the
** beginning of the page and all free space is collected
** into one big FreeBlk at the end of the page.
*/
static void defragmentPage(MemPage *pPage){
int pc, i, n;
FreeBlk *pFBlk;
char newPage[SQLITE_PAGE_SIZE];
assert( sqlitepager_iswriteable(pPage) );
pc = sizeof(PageHdr);
pPage->u.hdr.firstCell = pc;
memcpy(newPage, pPage->u.aDisk, pc);
for(i=0; i<pPage->nCell; i++){
Cell *pCell = pPage->apCell[i];
/* This routine should never be called on an overfull page. The
** following asserts verify that constraint. */
assert( Addr(pCell) > Addr(pPage) );
assert( Addr(pCell) < Addr(pPage) + SQLITE_PAGE_SIZE );
n = cellSize(pCell);
pCell->h.iNext = pc + n;
memcpy(&newPage[pc], pCell, n);
pPage->apCell[i] = (Cell*)&pPage->u.aDisk[pc];
pc += n;
}
assert( pPage->nFree==SQLITE_PAGE_SIZE-pc );
memcpy(pPage->u.aDisk, newPage, pc);
if( pPage->nCell>0 ){
pPage->apCell[pPage->nCell-1]->h.iNext = 0;
}
pFBlk = (FreeBlk*)&pPage->u.aDisk[pc];
pFBlk->iSize = SQLITE_PAGE_SIZE - pc;
pFBlk->iNext = 0;
pPage->u.hdr.firstFree = pc;
memset(&pFBlk[1], 0, SQLITE_PAGE_SIZE - pc - sizeof(FreeBlk));
}
/*
** Allocate nByte bytes of space on a page. nByte must be a
** multiple of 4.
**
** Return the index into pPage->u.aDisk[] of the first byte of
** the new allocation. Or return 0 if there is not enough free
** space on the page to satisfy the allocation request.
**
** If the page contains nBytes of free space but does not contain
** nBytes of contiguous free space, then this routine automatically
** calls defragementPage() to consolidate all free space before
** allocating the new chunk.
*/
static int allocateSpace(MemPage *pPage, int nByte){
FreeBlk *p;
u16 *pIdx;
int start;
int cnt = 0;
assert( sqlitepager_iswriteable(pPage) );
assert( nByte==ROUNDUP(nByte) );
if( pPage->nFree<nByte || pPage->isOverfull ) return 0;
pIdx = &pPage->u.hdr.firstFree;
p = (FreeBlk*)&pPage->u.aDisk[*pIdx];
while( p->iSize<nByte ){
assert( cnt++ < SQLITE_PAGE_SIZE/4 );
if( p->iNext==0 ){
defragmentPage(pPage);
pIdx = &pPage->u.hdr.firstFree;
}else{
pIdx = &p->iNext;
}
p = (FreeBlk*)&pPage->u.aDisk[*pIdx];
}
if( p->iSize==nByte ){
start = *pIdx;
*pIdx = p->iNext;
}else{
FreeBlk *pNew;
start = *pIdx;
pNew = (FreeBlk*)&pPage->u.aDisk[start + nByte];
pNew->iNext = p->iNext;
pNew->iSize = p->iSize - nByte;
*pIdx = start + nByte;
}
pPage->nFree -= nByte;
return start;
}
/*
** Return a section of the MemPage.u.aDisk[] to the freelist.
** The first byte of the new free block is pPage->u.aDisk[start]
** and the size of the block is "size" bytes. Size must be
** a multiple of 4.
**
** Most of the effort here is involved in coalesing adjacent
** free blocks into a single big free block.
*/
static void freeSpace(MemPage *pPage, int start, int size){
int end = start + size;
u16 *pIdx, idx;
FreeBlk *pFBlk;
FreeBlk *pNew;
FreeBlk *pNext;
assert( sqlitepager_iswriteable(pPage) );
assert( size == ROUNDUP(size) );
assert( start == ROUNDUP(start) );
pIdx = &pPage->u.hdr.firstFree;
idx = *pIdx;
while( idx!=0 && idx<start ){
pFBlk = (FreeBlk*)&pPage->u.aDisk[idx];
if( idx + pFBlk->iSize == start ){
pFBlk->iSize += size;
if( idx + pFBlk->iSize == pFBlk->iNext ){
pNext = (FreeBlk*)&pPage->u.aDisk[pFBlk->iNext];
pFBlk->iSize += pNext->iSize;
pFBlk->iNext = pNext->iNext;
}
pPage->nFree += size;
return;
}
pIdx = &pFBlk->iNext;
idx = *pIdx;
}
pNew = (FreeBlk*)&pPage->u.aDisk[start];
if( idx != end ){
pNew->iSize = size;
pNew->iNext = idx;
}else{
pNext = (FreeBlk*)&pPage->u.aDisk[idx];
pNew->iSize = size + pNext->iSize;
pNew->iNext = pNext->iNext;
}
*pIdx = start;
pPage->nFree += size;
}
/*
** Initialize the auxiliary information for a disk block.
**
** The pParent parameter must be a pointer to the MemPage which
** is the parent of the page being initialized. The root of the
** BTree (usually page 2) has no parent and so for that page,
** pParent==NULL.
**
** Return SQLITE_OK on success. If we see that the page does
** not contained a well-formed database page, then return
** SQLITE_CORRUPT. Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed. It only shows that
** we failed to detect any corruption.
*/
static int initPage(MemPage *pPage, Pgno pgnoThis, MemPage *pParent){
int idx; /* An index into pPage->u.aDisk[] */
Cell *pCell; /* A pointer to a Cell in pPage->u.aDisk[] */
FreeBlk *pFBlk; /* A pointer to a free block in pPage->u.aDisk[] */
int sz; /* The size of a Cell in bytes */
int freeSpace; /* Amount of free space on the page */
if( pPage->pParent ){
assert( pPage->pParent==pParent );
return SQLITE_OK;
}
if( pParent ){
pPage->pParent = pParent;
sqlitepager_ref(pParent);
}
if( pPage->isInit ) return SQLITE_OK;
pPage->isInit = 1;
pPage->nCell = 0;
freeSpace = USABLE_SPACE;
idx = pPage->u.hdr.firstCell;
while( idx!=0 ){
if( idx>SQLITE_PAGE_SIZE-MIN_CELL_SIZE ) goto page_format_error;
if( idx<sizeof(PageHdr) ) goto page_format_error;
if( idx!=ROUNDUP(idx) ) goto page_format_error;
pCell = (Cell*)&pPage->u.aDisk[idx];
sz = cellSize(pCell);
if( idx+sz > SQLITE_PAGE_SIZE ) goto page_format_error;
freeSpace -= sz;
pPage->apCell[pPage->nCell++] = pCell;
idx = pCell->h.iNext;
}
pPage->nFree = 0;
idx = pPage->u.hdr.firstFree;
while( idx!=0 ){
if( idx>SQLITE_PAGE_SIZE-sizeof(FreeBlk) ) goto page_format_error;
if( idx<sizeof(PageHdr) ) goto page_format_error;
pFBlk = (FreeBlk*)&pPage->u.aDisk[idx];
pPage->nFree += pFBlk->iSize;
if( pFBlk->iNext>0 && pFBlk->iNext <= idx ) goto page_format_error;
idx = pFBlk->iNext;
}
if( pPage->nCell==0 && pPage->nFree==0 ){
/* As a special case, an uninitialized root page appears to be
** an empty database */
return SQLITE_OK;
}
if( pPage->nFree!=freeSpace ) goto page_format_error;
return SQLITE_OK;
page_format_error:
return SQLITE_CORRUPT;
}
/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
static void zeroPage(MemPage *pPage){
PageHdr *pHdr;
FreeBlk *pFBlk;
assert( sqlitepager_iswriteable(pPage) );
memset(pPage, 0, SQLITE_PAGE_SIZE);
pHdr = &pPage->u.hdr;
pHdr->firstCell = 0;
pHdr->firstFree = sizeof(*pHdr);
pFBlk = (FreeBlk*)&pHdr[1];
pFBlk->iNext = 0;
pFBlk->iSize = SQLITE_PAGE_SIZE - sizeof(*pHdr);
pPage->nFree = pFBlk->iSize;
pPage->nCell = 0;
pPage->isOverfull = 0;
}
/*
** This routine is called when the reference count for a page
** reaches zero. We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData){
MemPage *pPage = (MemPage*)pData;
if( pPage->pParent ){
MemPage *pParent = pPage->pParent;
pPage->pParent = 0;
sqlitepager_unref(pParent);
}
}
/*
** Open a new database.
**
** Actually, this routine just sets up the internal data structures
** for accessing the database. We do not open the database file
** until the first page is loaded.
**
** zFilename is the name of the database file. If zFilename is NULL
** a new database with a random name is created. This randomly named
** database file will be deleted when sqliteBtreeClose() is called.
*/
int sqliteBtreeOpen(
const char *zFilename, /* Name of the file containing the BTree database */
int mode, /* Not currently used */
int nCache, /* How many pages in the page cache */
Btree **ppBtree /* Pointer to new Btree object written here */
){
Btree *pBt;
int rc;
pBt = sqliteMalloc( sizeof(*pBt) );
if( pBt==0 ){
*ppBtree = 0;
return SQLITE_NOMEM;
}
if( nCache<10 ) nCache = 10;
rc = sqlitepager_open(&pBt->pPager, zFilename, nCache, EXTRA_SIZE);
if( rc!=SQLITE_OK ){
if( pBt->pPager ) sqlitepager_close(pBt->pPager);
sqliteFree(pBt);
*ppBtree = 0;
return rc;
}
sqlitepager_set_destructor(pBt->pPager, pageDestructor);
pBt->pCursor = 0;
pBt->page1 = 0;
pBt->readOnly = sqlitepager_isreadonly(pBt->pPager);
sqliteHashInit(&pBt->locks, SQLITE_HASH_INT, 0);
*ppBtree = pBt;
return SQLITE_OK;
}
/*
** Close an open database and invalidate all cursors.
*/
int sqliteBtreeClose(Btree *pBt){
while( pBt->pCursor ){
sqliteBtreeCloseCursor(pBt->pCursor);
}
sqlitepager_close(pBt->pPager);
sqliteHashClear(&pBt->locks);
sqliteFree(pBt);
return SQLITE_OK;
}
/*
** Change the limit on the number of pages allowed the cache.
**
** The maximum number of cache pages is set to the absolute
** value of mxPage. If mxPage is negative, the pager will
** operate asynchronously - it will not stop to do fsync()s
** to insure data is written to the disk surface before
** continuing. Transactions still work if synchronous is off,
** and the database cannot be corrupted if this program
** crashes. But if the operating system crashes or there is
** an abrupt power failure when synchronous is off, the database
** could be left in an inconsistent and unrecoverable state.
** Synchronous is on by default so database corruption is not
** normally a worry.
*/
int sqliteBtreeSetCacheSize(Btree *pBt, int mxPage){
sqlitepager_set_cachesize(pBt->pPager, mxPage);
return SQLITE_OK;
}
/*
** Get a reference to page1 of the database file. This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success. If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked. SQLITE_NOMEM
** is returned if we run out of memory. SQLITE_PROTOCOL is returned
** if there is a locking protocol violation.
*/
static int lockBtree(Btree *pBt){
int rc;
if( pBt->page1 ) return SQLITE_OK;
rc = sqlitepager_get(pBt->pPager, 1, (void**)&pBt->page1);
if( rc!=SQLITE_OK ) return rc;
/* Do some checking to help insure the file we opened really is
** a valid database file.
*/
if( sqlitepager_pagecount(pBt->pPager)>0 ){
PageOne *pP1 = pBt->page1;
if( strcmp(pP1->zMagic,zMagicHeader)!=0 || pP1->iMagic!=MAGIC ){
rc = SQLITE_CORRUPT;
goto page1_init_failed;
}
}
return rc;
page1_init_failed:
sqlitepager_unref(pBt->page1);
pBt->page1 = 0;
return rc;
}
/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which
** has the effect of releasing the read lock.
**
** If there are any outstanding cursors, this routine is a no-op.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(Btree *pBt){
if( pBt->inTrans==0 && pBt->pCursor==0 && pBt->page1!=0 ){
sqlitepager_unref(pBt->page1);
pBt->page1 = 0;
pBt->inTrans = 0;
pBt->inCkpt = 0;
}
}
/*
** Create a new database by initializing the first two pages of the
** file.
*/
static int newDatabase(Btree *pBt){
MemPage *pRoot;
PageOne *pP1;
int rc;
if( sqlitepager_pagecount(pBt->pPager)>1 ) return SQLITE_OK;
pP1 = pBt->page1;
rc = sqlitepager_write(pBt->page1);
if( rc ) return rc;
rc = sqlitepager_get(pBt->pPager, 2, (void**)&pRoot);
if( rc ) return rc;
rc = sqlitepager_write(pRoot);
if( rc ){
sqlitepager_unref(pRoot);
return rc;
}
strcpy(pP1->zMagic, zMagicHeader);
pP1->iMagic = MAGIC;
zeroPage(pRoot);
sqlitepager_unref(pRoot);
return SQLITE_OK;
}
/*
** Attempt to start a new transaction.
**
** A transaction must be started before attempting any changes
** to the database. None of the following routines will work
** unless a transaction is started first:
**
** sqliteBtreeCreateTable()
** sqliteBtreeCreateIndex()
** sqliteBtreeClearTable()
** sqliteBtreeDropTable()
** sqliteBtreeInsert()
** sqliteBtreeDelete()
** sqliteBtreeUpdateMeta()
*/
int sqliteBtreeBeginTrans(Btree *pBt){
int rc;
if( pBt->inTrans ) return SQLITE_ERROR;
if( pBt->page1==0 ){
rc = lockBtree(pBt);
if( rc!=SQLITE_OK ){
return rc;
}
}
if( pBt->readOnly ){
rc = SQLITE_OK;
}else{
rc = sqlitepager_begin(pBt->page1);
if( rc==SQLITE_OK ){
rc = newDatabase(pBt);
}
}
if( rc==SQLITE_OK ){
pBt->inTrans = 1;
pBt->inCkpt = 0;
}else{
unlockBtreeIfUnused(pBt);
}
return rc;
}
/*
** Commit the transaction currently in progress.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqliteBtreeCommit(Btree *pBt){
int rc;
if( pBt->inTrans==0 ) return SQLITE_ERROR;
rc = pBt->readOnly ? SQLITE_OK : sqlitepager_commit(pBt->pPager);
pBt->inTrans = 0;
pBt->inCkpt = 0;
unlockBtreeIfUnused(pBt);
return rc;
}
/*
** Rollback the transaction in progress. All cursors will be
** invalided by this operation. Any attempt to use a cursor
** that was open at the beginning of this operation will result
** in an error.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqliteBtreeRollback(Btree *pBt){
int rc;
BtCursor *pCur;
if( pBt->inTrans==0 ) return SQLITE_OK;
pBt->inTrans = 0;
pBt->inCkpt = 0;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->pPage ){
sqlitepager_unref(pCur->pPage);
pCur->pPage = 0;
}
}
rc = pBt->readOnly ? SQLITE_OK : sqlitepager_rollback(pBt->pPager);
unlockBtreeIfUnused(pBt);
return rc;
}
/*
** Set the checkpoint for the current transaction. The checkpoint serves
** as a sub-transaction that can be rolled back independently of the
** main transaction. You must start a transaction before starting a
** checkpoint. The checkpoint is ended automatically if the transaction
** commits or rolls back.
**
** Only one checkpoint may be active at a time. It is an error to try
** to start a new checkpoint if another checkpoint is already active.
*/
int sqliteBtreeBeginCkpt(Btree *pBt){
int rc;
if( !pBt->inTrans || pBt->inCkpt ){
return SQLITE_ERROR;
}
rc = pBt->readOnly ? SQLITE_OK : sqlitepager_ckpt_begin(pBt->pPager);
pBt->inCkpt = 1;
return rc;
}
/*
** Commit a checkpoint to transaction currently in progress. If no
** checkpoint is active, this is a no-op.
*/
int sqliteBtreeCommitCkpt(Btree *pBt){
int rc;
if( pBt->inCkpt && !pBt->readOnly ){
rc = sqlitepager_ckpt_commit(pBt->pPager);
}else{
rc = SQLITE_OK;
}
pBt->inCkpt = 0;
return rc;
}
/*
** Rollback the checkpoint to the current transaction. If there
** is no active checkpoint or transaction, this routine is a no-op.
**
** All cursors will be invalided by this operation. Any attempt
** to use a cursor that was open at the beginning of this operation
** will result in an error.
*/
int sqliteBtreeRollbackCkpt(Btree *pBt){
int rc;
BtCursor *pCur;
if( pBt->inCkpt==0 || pBt->readOnly ) return SQLITE_OK;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->pPage ){
sqlitepager_unref(pCur->pPage);
pCur->pPage = 0;
}
}
rc = sqlitepager_ckpt_rollback(pBt->pPager);
pBt->inCkpt = 0;
return rc;
}
/*
** Create a new cursor for the BTree whose root is on the page
** iTable. The act of acquiring a cursor gets a read lock on
** the database file.
**
** If wrFlag==0, then the cursor can only be used for reading.
** If wrFlag==1, then the cursor can be used for reading or writing.
** A read/write cursor requires exclusive access to its table. There
** cannot be two or more cursors open on the same table if any one of
** cursors is a read/write cursor. But there can be two or more
** read-only cursors open on the same table.
**
** No checking is done to make sure that page iTable really is the
** root page of a b-tree. If it is not, then the cursor acquired
** will not work correctly.
*/
int sqliteBtreeCursor(Btree *pBt, int iTable, int wrFlag, BtCursor **ppCur){
int rc;
BtCursor *pCur;
ptr nLock;
if( pBt->page1==0 ){
rc = lockBtree(pBt);
if( rc!=SQLITE_OK ){
*ppCur = 0;
return rc;
}
}
if( wrFlag && pBt->readOnly ){
*ppCur = 0;
return SQLITE_READONLY;
}
pCur = sqliteMalloc( sizeof(*pCur) );
if( pCur==0 ){
rc = SQLITE_NOMEM;
goto create_cursor_exception;
}
pCur->pgnoRoot = (Pgno)iTable;
rc = sqlitepager_get(pBt->pPager, pCur->pgnoRoot, (void**)&pCur->pPage);
if( rc!=SQLITE_OK ){
goto create_cursor_exception;
}
rc = initPage(pCur->pPage, pCur->pgnoRoot, 0);
if( rc!=SQLITE_OK ){
goto create_cursor_exception;
}
nLock = (ptr)sqliteHashFind(&pBt->locks, 0, iTable);
if( nLock<0 || (nLock>0 && wrFlag) ){
rc = SQLITE_LOCKED;
goto create_cursor_exception;
}
nLock = wrFlag ? -1 : nLock+1;
sqliteHashInsert(&pBt->locks, 0, iTable, (void*)nLock);
pCur->pBt = pBt;
pCur->wrFlag = wrFlag;
pCur->idx = 0;
pCur->pNext = pBt->pCursor;
if( pCur->pNext ){
pCur->pNext->pPrev = pCur;
}
pCur->pPrev = 0;
pBt->pCursor = pCur;
*ppCur = pCur;
return SQLITE_OK;
create_cursor_exception:
*ppCur = 0;
if( pCur ){
if( pCur->pPage ) sqlitepager_unref(pCur->pPage);
sqliteFree(pCur);
}
unlockBtreeIfUnused(pBt);
return rc;
}
/*
** Close a cursor. The read lock on the database file is released
** when the last cursor is closed.
*/
int sqliteBtreeCloseCursor(BtCursor *pCur){
ptr nLock;
Btree *pBt = pCur->pBt;
if( pCur->pPrev ){
pCur->pPrev->pNext = pCur->pNext;
}else{
pBt->pCursor = pCur->pNext;
}
if( pCur->pNext ){
pCur->pNext->pPrev = pCur->pPrev;
}
if( pCur->pPage ){
sqlitepager_unref(pCur->pPage);
}
unlockBtreeIfUnused(pBt);
nLock = (ptr)sqliteHashFind(&pBt->locks, 0, pCur->pgnoRoot);
assert( nLock!=0 || sqlite_malloc_failed );
nLock = nLock<0 ? 0 : nLock-1;
sqliteHashInsert(&pBt->locks, 0, pCur->pgnoRoot, (void*)nLock);
sqliteFree(pCur);
return SQLITE_OK;
}
/*
** Make a temporary cursor by filling in the fields of pTempCur.
** The temporary cursor is not on the cursor list for the Btree.
*/
static void getTempCursor(BtCursor *pCur, BtCursor *pTempCur){
memcpy(pTempCur, pCur, sizeof(*pCur));
pTempCur->pNext = 0;
pTempCur->pPrev = 0;
if( pTempCur->pPage ){
sqlitepager_ref(pTempCur->pPage);
}
}
/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
static void releaseTempCursor(BtCursor *pCur){
if( pCur->pPage ){
sqlitepager_unref(pCur->pPage);
}
}
/*
** Set *pSize to the number of bytes of key in the entry the
** cursor currently points to. Always return SQLITE_OK.
** Failure is not possible. If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqliteBtreeKeySize(BtCursor *pCur, int *pSize){
Cell *pCell;
MemPage *pPage;
pPage = pCur->pPage;
if( pPage==0 || pCur->idx >= pPage->nCell ){
*pSize = 0;
}else{
pCell = pPage->apCell[pCur->idx];
*pSize = NKEY(pCell->h);
}
return SQLITE_OK;
}
/*
** Read payload information from the entry that the pCur cursor is
** pointing to. Begin reading the payload at "offset" and read
** a total of "amt" bytes. Put the result in zBuf.
**
** This routine does not make a distinction between key and data.
** It just reads bytes from the payload area.
*/
static int getPayload(BtCursor *pCur, int offset, int amt, char *zBuf){
char *aPayload;
Pgno nextPage;
int rc;
assert( pCur!=0 && pCur->pPage!=0 );
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
aPayload = pCur->pPage->apCell[pCur->idx]->aPayload;
if( offset<MX_LOCAL_PAYLOAD ){
int a = amt;
if( a+offset>MX_LOCAL_PAYLOAD ){
a = MX_LOCAL_PAYLOAD - offset;
}
memcpy(zBuf, &aPayload[offset], a);
if( a==amt ){
return SQLITE_OK;
}
offset = 0;
zBuf += a;
amt -= a;
}else{
offset -= MX_LOCAL_PAYLOAD;
}
if( amt>0 ){
nextPage = pCur->pPage->apCell[pCur->idx]->ovfl;
}
while( amt>0 && nextPage ){
OverflowPage *pOvfl;
rc = sqlitepager_get(pCur->pBt->pPager, nextPage, (void**)&pOvfl);
if( rc!=0 ){
return rc;
}
nextPage = pOvfl->iNext;
if( offset<OVERFLOW_SIZE ){
int a = amt;
if( a + offset > OVERFLOW_SIZE ){
a = OVERFLOW_SIZE - offset;
}
memcpy(zBuf, &pOvfl->aPayload[offset], a);
offset = 0;
amt -= a;
zBuf += a;
}else{
offset -= OVERFLOW_SIZE;
}
sqlitepager_unref(pOvfl);
}
if( amt>0 ){
return SQLITE_CORRUPT;
}
return SQLITE_OK;
}
/*
** Read part of the key associated with cursor pCur. A maximum
** of "amt" bytes will be transfered into zBuf[]. The transfer
** begins at "offset". The number of bytes actually read is
** returned. The amount returned will be smaller than the
** amount requested if there are not enough bytes in the key
** to satisfy the request.
*/
int sqliteBtreeKey(BtCursor *pCur, int offset, int amt, char *zBuf){
Cell *pCell;
MemPage *pPage;
if( amt<0 ) return 0;
if( offset<0 ) return 0;
if( amt==0 ) return 0;
pPage = pCur->pPage;
if( pPage==0 ) return 0;
if( pCur->idx >= pPage->nCell ){
return 0;
}
pCell = pPage->apCell[pCur->idx];
if( amt+offset > NKEY(pCell->h) ){
amt = NKEY(pCell->h) - offset;
if( amt<=0 ){
return 0;
}
}
getPayload(pCur, offset, amt, zBuf);
return amt;
}
/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to. Always return SQLITE_OK.
** Failure is not possible. If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqliteBtreeDataSize(BtCursor *pCur, int *pSize){
Cell *pCell;
MemPage *pPage;
pPage = pCur->pPage;
if( pPage==0 || pCur->idx >= pPage->nCell ){
*pSize = 0;
}else{
pCell = pPage->apCell[pCur->idx];
*pSize = NDATA(pCell->h);
}
return SQLITE_OK;
}
/*
** Read part of the data associated with cursor pCur. A maximum
** of "amt" bytes will be transfered into zBuf[]. The transfer
** begins at "offset". The number of bytes actually read is
** returned. The amount returned will be smaller than the
** amount requested if there are not enough bytes in the data
** to satisfy the request.
*/
int sqliteBtreeData(BtCursor *pCur, int offset, int amt, char *zBuf){
Cell *pCell;
MemPage *pPage;
if( amt<0 ) return 0;
if( offset<0 ) return 0;
if( amt==0 ) return 0;
pPage = pCur->pPage;
if( pPage==0 || pCur->idx >= pPage->nCell ){
return 0;
}
pCell = pPage->apCell[pCur->idx];
if( amt+offset > NDATA(pCell->h) ){
amt = NDATA(pCell->h) - offset;
if( amt<=0 ){
return 0;
}
}
getPayload(pCur, offset + NKEY(pCell->h), amt, zBuf);
return amt;
}
/*
** Compare an external key against the key on the entry that pCur points to.
**
** The external key is pKey and is nKey bytes long. The last nIgnore bytes
** of the key associated with pCur are ignored, as if they do not exist.
** (The normal case is for nIgnore to be zero in which case the entire
** internal key is used in the comparison.)
**
** The comparison result is written to *pRes as follows:
**
** *pRes<0 This means pCur<pKey
**
** *pRes==0 This means pCur==pKey for all nKey bytes
**
** *pRes>0 This means pCur>pKey
**
** When one key is an exact prefix of the other, the shorter key is
** considered less than the longer one. In order to be equal the
** keys must be exactly the same length. (The length of the pCur key
** is the actual key length minus nIgnore bytes.)
*/
int sqliteBtreeKeyCompare(
BtCursor *pCur, /* Pointer to entry to compare against */
const void *pKey, /* Key to compare against entry that pCur points to */
int nKey, /* Number of bytes in pKey */
int nIgnore, /* Ignore this many bytes at the end of pCur */
int *pResult /* Write the result here */
){
Pgno nextPage;
int n, c, rc, nLocal;
Cell *pCell;
const char *zKey = (const char*)pKey;
assert( pCur->pPage );
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
pCell = pCur->pPage->apCell[pCur->idx];
nLocal = NKEY(pCell->h) - nIgnore;
if( nLocal<0 ) nLocal = 0;
n = nKey<nLocal ? nKey : nLocal;
if( n>MX_LOCAL_PAYLOAD ){
n = MX_LOCAL_PAYLOAD;
}
c = memcmp(pCell->aPayload, zKey, n);
if( c!=0 ){
*pResult = c;
return SQLITE_OK;
}
zKey += n;
nKey -= n;
nLocal -= n;
nextPage = pCell->ovfl;
while( nKey>0 && nLocal>0 ){
OverflowPage *pOvfl;
if( nextPage==0 ){
return SQLITE_CORRUPT;
}
rc = sqlitepager_get(pCur->pBt->pPager, nextPage, (void**)&pOvfl);
if( rc ){
return rc;
}
nextPage = pOvfl->iNext;
n = nKey<nLocal ? nKey : nLocal;
if( n>OVERFLOW_SIZE ){
n = OVERFLOW_SIZE;
}
c = memcmp(pOvfl->aPayload, zKey, n);
sqlitepager_unref(pOvfl);
if( c!=0 ){
*pResult = c;
return SQLITE_OK;
}
nKey -= n;
nLocal -= n;
zKey += n;
}
if( c==0 ){
c = nLocal - nKey;
}
*pResult = c;
return SQLITE_OK;
}
/*
** Move the cursor down to a new child page.
*/
static int moveToChild(BtCursor *pCur, int newPgno){
int rc;
MemPage *pNewPage;
rc = sqlitepager_get(pCur->pBt->pPager, newPgno, (void**)&pNewPage);
if( rc ) return rc;
rc = initPage(pNewPage, newPgno, pCur->pPage);
if( rc ) return rc;
sqlitepager_unref(pCur->pPage);
pCur->pPage = pNewPage;
pCur->idx = 0;
return SQLITE_OK;
}
/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from. If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static int moveToParent(BtCursor *pCur){
Pgno oldPgno;
MemPage *pParent;
int i;
pParent = pCur->pPage->pParent;
if( pParent==0 ) return SQLITE_INTERNAL;
oldPgno = sqlitepager_pagenumber(pCur->pPage);
sqlitepager_ref(pParent);
sqlitepager_unref(pCur->pPage);
pCur->pPage = pParent;
pCur->idx = pParent->nCell;
for(i=0; i<pParent->nCell; i++){
if( pParent->apCell[i]->h.leftChild==oldPgno ){
pCur->idx = i;
break;
}
}
return SQLITE_OK;
}
/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
MemPage *pNew;
int rc;
rc = sqlitepager_get(pCur->pBt->pPager, pCur->pgnoRoot, (void**)&pNew);
if( rc ) return rc;
rc = initPage(pNew, pCur->pgnoRoot, 0);
if( rc ) return rc;
sqlitepager_unref(pCur->pPage);
pCur->pPage = pNew;
pCur->idx = 0;
return SQLITE_OK;
}
/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
*/
static int moveToLeftmost(BtCursor *pCur){
Pgno pgno;
int rc;
while( (pgno = pCur->pPage->apCell[pCur->idx]->h.leftChild)!=0 ){
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
}
return SQLITE_OK;
}
/* Move the cursor to the first entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqliteBtreeFirst(BtCursor *pCur, int *pRes){
int rc;
if( pCur->pPage==0 ) return SQLITE_ABORT;
rc = moveToRoot(pCur);
if( rc ) return rc;
if( pCur->pPage->nCell==0 ){
*pRes = 1;
return SQLITE_OK;
}
*pRes = 0;
rc = moveToLeftmost(pCur);
pCur->bSkipNext = 0;
return rc;
}
/* Move the cursor to the last entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqliteBtreeLast(BtCursor *pCur, int *pRes){
int rc;
Pgno pgno;
if( pCur->pPage==0 ) return SQLITE_ABORT;
rc = moveToRoot(pCur);
if( rc ) return rc;
if( pCur->pPage->nCell==0 ){
*pRes = 1;
return SQLITE_OK;
}
*pRes = 0;
while( (pgno = pCur->pPage->u.hdr.rightChild)!=0 ){
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
}
pCur->idx = pCur->pPage->nCell-1;
pCur->bSkipNext = 0;
return rc;
}
/* Move the cursor so that it points to an entry near pKey.
** Return a success code.
**
** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present. The cursor might point to an entry that comes
** before or after the key.
**
** The result of comparing the key with the entry to which the
** cursor is left pointing is stored in pCur->iMatch. The same
** value is also written to *pRes if pRes!=NULL. The meaning of
** this value is as follows:
**
** *pRes<0 The cursor is left pointing at an entry that
** is smaller than pKey.
**
** *pRes==0 The cursor is left pointing at an entry that
** exactly matches pKey.
**
** *pRes>0 The cursor is left pointing at an entry that
** is larger than pKey.
*/
int sqliteBtreeMoveto(BtCursor *pCur, const void *pKey, int nKey, int *pRes){
int rc;
if( pCur->pPage==0 ) return SQLITE_ABORT;
pCur->bSkipNext = 0;
rc = moveToRoot(pCur);
if( rc ) return rc;
for(;;){
int lwr, upr;
Pgno chldPg;
MemPage *pPage = pCur->pPage;
int c = -1;
lwr = 0;
upr = pPage->nCell-1;
while( lwr<=upr ){
pCur->idx = (lwr+upr)/2;
rc = sqliteBtreeKeyCompare(pCur, pKey, nKey, 0, &c);
if( rc ) return rc;
if( c==0 ){
pCur->iMatch = c;
if( pRes ) *pRes = 0;
return SQLITE_OK;
}
if( c<0 ){
lwr = pCur->idx+1;
}else{
upr = pCur->idx-1;
}
}
assert( lwr==upr+1 );
if( lwr>=pPage->nCell ){
chldPg = pPage->u.hdr.rightChild;
}else{
chldPg = pPage->apCell[lwr]->h.leftChild;
}
if( chldPg==0 ){
pCur->iMatch = c;
if( pRes ) *pRes = c;
return SQLITE_OK;
}
rc = moveToChild(pCur, chldPg);
if( rc ) return rc;
}
/* NOT REACHED */
}
/*
** Advance the cursor to the next entry in the database. If
** successful and pRes!=NULL then set *pRes=0. If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1 if pRes!=NULL.
*/
int sqliteBtreeNext(BtCursor *pCur, int *pRes){
int rc;
if( pCur->pPage==0 ){
if( pRes ) *pRes = 1;
return SQLITE_ABORT;
}
if( pCur->bSkipNext && pCur->idx<pCur->pPage->nCell ){
pCur->bSkipNext = 0;
if( pRes ) *pRes = 0;
return SQLITE_OK;
}
pCur->idx++;
if( pCur->idx>=pCur->pPage->nCell ){
if( pCur->pPage->u.hdr.rightChild ){
rc = moveToChild(pCur, pCur->pPage->u.hdr.rightChild);
if( rc ) return rc;
rc = moveToLeftmost(pCur);
if( rc ) return rc;
if( pRes ) *pRes = 0;
return SQLITE_OK;
}
do{
if( pCur->pPage->pParent==0 ){
if( pRes ) *pRes = 1;
return SQLITE_OK;
}
rc = moveToParent(pCur);
if( rc ) return rc;
}while( pCur->idx>=pCur->pPage->nCell );
if( pRes ) *pRes = 0;
return SQLITE_OK;
}
rc = moveToLeftmost(pCur);
if( rc ) return rc;
if( pRes ) *pRes = 0;
return SQLITE_OK;
}
/*
** Allocate a new page from the database file.
**
** The new page is marked as dirty. (In other words, sqlitepager_write()
** has already been called on the new page.) The new page has also
** been referenced and the calling routine is responsible for calling
** sqlitepager_unref() on the new page when it is done.
**
** SQLITE_OK is returned on success. Any other return value indicates
** an error. *ppPage and *pPgno are undefined in the event of an error.
** Do not invoke sqlitepager_unref() on *ppPage if an error is returned.
*/
static int allocatePage(Btree *pBt, MemPage **ppPage, Pgno *pPgno){
PageOne *pPage1 = pBt->page1;
int rc;
if( pPage1->freeList ){
OverflowPage *pOvfl;
FreelistInfo *pInfo;
rc = sqlitepager_write(pPage1);
if( rc ) return rc;
pPage1->nFree--;
rc = sqlitepager_get(pBt->pPager, pPage1->freeList, (void**)&pOvfl);
if( rc ) return rc;
rc = sqlitepager_write(pOvfl);
if( rc ){
sqlitepager_unref(pOvfl);
return rc;
}
pInfo = (FreelistInfo*)pOvfl->aPayload;
if( pInfo->nFree==0 ){
*pPgno = pPage1->freeList;
pPage1->freeList = pOvfl->iNext;
*ppPage = (MemPage*)pOvfl;
}else{
pInfo->nFree--;
*pPgno = pInfo->aFree[pInfo->nFree];
rc = sqlitepager_get(pBt->pPager, *pPgno, (void**)ppPage);
sqlitepager_unref(pOvfl);
if( rc==SQLITE_OK ){
sqlitepager_dont_rollback(*ppPage);
rc = sqlitepager_write(*ppPage);
}
}
}else{
*pPgno = sqlitepager_pagecount(pBt->pPager) + 1;
rc = sqlitepager_get(pBt->pPager, *pPgno, (void**)ppPage);
if( rc ) return rc;
rc = sqlitepager_write(*ppPage);
}
return rc;
}
/*
** Add a page of the database file to the freelist. Either pgno or
** pPage but not both may be 0.
**
** sqlitepager_unref() is NOT called for pPage.
*/
static int freePage(Btree *pBt, void *pPage, Pgno pgno){
PageOne *pPage1 = pBt->page1;
OverflowPage *pOvfl = (OverflowPage*)pPage;
int rc;
int needUnref = 0;
MemPage *pMemPage;
if( pgno==0 ){
assert( pOvfl!=0 );
pgno = sqlitepager_pagenumber(pOvfl);
}
assert( pgno>2 );
rc = sqlitepager_write(pPage1);
if( rc ){
return rc;
}
pPage1->nFree++;
if( pPage1->nFree>0 && pPage1->freeList ){
OverflowPage *pFreeIdx;
rc = sqlitepager_get(pBt->pPager, pPage1->freeList, (void**)&pFreeIdx);
if( rc==SQLITE_OK ){
FreelistInfo *pInfo = (FreelistInfo*)pFreeIdx->aPayload;
if( pInfo->nFree<(sizeof(pInfo->aFree)/sizeof(pInfo->aFree[0])) ){
rc = sqlitepager_write(pFreeIdx);
if( rc==SQLITE_OK ){
pInfo->aFree[pInfo->nFree] = pgno;
pInfo->nFree++;
sqlitepager_unref(pFreeIdx);
sqlitepager_dont_write(pBt->pPager, pgno);
return rc;
}
}
sqlitepager_unref(pFreeIdx);
}
}
if( pOvfl==0 ){
assert( pgno>0 );
rc = sqlitepager_get(pBt->pPager, pgno, (void**)&pOvfl);
if( rc ) return rc;
needUnref = 1;
}
rc = sqlitepager_write(pOvfl);
if( rc ){
if( needUnref ) sqlitepager_unref(pOvfl);
return rc;
}
pOvfl->iNext = pPage1->freeList;
pPage1->freeList = pgno;
memset(pOvfl->aPayload, 0, OVERFLOW_SIZE);
pMemPage = (MemPage*)pPage;
pMemPage->isInit = 0;
if( pMemPage->pParent ){
sqlitepager_unref(pMemPage->pParent);
pMemPage->pParent = 0;
}
if( needUnref ) rc = sqlitepager_unref(pOvfl);
return rc;
}
/*
** Erase all the data out of a cell. This involves returning overflow
** pages back the freelist.
*/
static int clearCell(Btree *pBt, Cell *pCell){
Pager *pPager = pBt->pPager;
OverflowPage *pOvfl;
Pgno ovfl, nextOvfl;
int rc;
if( NKEY(pCell->h) + NDATA(pCell->h) <= MX_LOCAL_PAYLOAD ){
return SQLITE_OK;
}
ovfl = pCell->ovfl;
pCell->ovfl = 0;
while( ovfl ){
rc = sqlitepager_get(pPager, ovfl, (void**)&pOvfl);
if( rc ) return rc;
nextOvfl = pOvfl->iNext;
rc = freePage(pBt, pOvfl, ovfl);
if( rc ) return rc;
sqlitepager_unref(pOvfl);
ovfl = nextOvfl;
}
return SQLITE_OK;
}
/*
** Create a new cell from key and data. Overflow pages are allocated as
** necessary and linked to this cell.
*/
static int fillInCell(
Btree *pBt, /* The whole Btree. Needed to allocate pages */
Cell *pCell, /* Populate this Cell structure */
const void *pKey, int nKey, /* The key */
const void *pData,int nData /* The data */
){
OverflowPage *pOvfl, *pPrior;
Pgno *pNext;
int spaceLeft;
int n, rc;
int nPayload;
const char *pPayload;
char *pSpace;
pCell->h.leftChild = 0;
pCell->h.nKey = nKey & 0xffff;
pCell->h.nKeyHi = nKey >> 16;
pCell->h.nData = nData & 0xffff;
pCell->h.nDataHi = nData >> 16;
pCell->h.iNext = 0;
pNext = &pCell->ovfl;
pSpace = pCell->aPayload;
spaceLeft = MX_LOCAL_PAYLOAD;
pPayload = pKey;
pKey = 0;
nPayload = nKey;
pPrior = 0;
while( nPayload>0 ){
if( spaceLeft==0 ){
rc = allocatePage(pBt, (MemPage**)&pOvfl, pNext);
if( rc ){
*pNext = 0;
}
if( pPrior ) sqlitepager_unref(pPrior);
if( rc ){
clearCell(pBt, pCell);
return rc;
}
pPrior = pOvfl;
spaceLeft = OVERFLOW_SIZE;
pSpace = pOvfl->aPayload;
pNext = &pOvfl->iNext;
}
n = nPayload;
if( n>spaceLeft ) n = spaceLeft;
memcpy(pSpace, pPayload, n);
nPayload -= n;
if( nPayload==0 && pData ){
pPayload = pData;
nPayload = nData;
pData = 0;
}else{
pPayload += n;
}
spaceLeft -= n;
pSpace += n;
}
*pNext = 0;
if( pPrior ){
sqlitepager_unref(pPrior);
}
return SQLITE_OK;
}
/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
** pointer in the third argument.
*/
static void reparentPage(Pager *pPager, Pgno pgno, MemPage *pNewParent){
MemPage *pThis;
if( pgno==0 ) return;
assert( pPager!=0 );
pThis = sqlitepager_lookup(pPager, pgno);
if( pThis && pThis->isInit ){
if( pThis->pParent!=pNewParent ){
if( pThis->pParent ) sqlitepager_unref(pThis->pParent);
pThis->pParent = pNewParent;
if( pNewParent ) sqlitepager_ref(pNewParent);
}
sqlitepager_unref(pThis);
}
}
/*
** Reparent all children of the given page to be the given page.
** In other words, for every child of pPage, invoke reparentPage()
** to make sure that each child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
*/
static void reparentChildPages(Pager *pPager, MemPage *pPage){
int i;
for(i=0; i<pPage->nCell; i++){
reparentPage(pPager, pPage->apCell[i]->h.leftChild, pPage);
}
reparentPage(pPager, pPage->u.hdr.rightChild, pPage);
}
/*
** Remove the i-th cell from pPage. This routine effects pPage only.
** The cell content is not freed or deallocated. It is assumed that
** the cell content has been copied someplace else. This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
**
** Do not bother maintaining the integrity of the linked list of Cells.
** Only the pPage->apCell[] array is important. The relinkCellList()
** routine will be called soon after this routine in order to rebuild
** the linked list.
*/
static void dropCell(MemPage *pPage, int idx, int sz){
int j;
assert( idx>=0 && idx<pPage->nCell );
assert( sz==cellSize(pPage->apCell[idx]) );
assert( sqlitepager_iswriteable(pPage) );
freeSpace(pPage, Addr(pPage->apCell[idx]) - Addr(pPage), sz);
for(j=idx; j<pPage->nCell-1; j++){
pPage->apCell[j] = pPage->apCell[j+1];
}
pPage->nCell--;
}
/*
** Insert a new cell on pPage at cell index "i". pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there. If it
** will not fit, then just make pPage->apCell[i] point to the content
** and set pPage->isOverfull.
**
** Do not bother maintaining the integrity of the linked list of Cells.
** Only the pPage->apCell[] array is important. The relinkCellList()
** routine will be called soon after this routine in order to rebuild
** the linked list.
*/
static void insertCell(MemPage *pPage, int i, Cell *pCell, int sz){
int idx, j;
assert( i>=0 && i<=pPage->nCell );
assert( sz==cellSize(pCell) );
assert( sqlitepager_iswriteable(pPage) );
idx = allocateSpace(pPage, sz);
for(j=pPage->nCell; j>i; j--){
pPage->apCell[j] = pPage->apCell[j-1];
}
pPage->nCell++;
if( idx<=0 ){
pPage->isOverfull = 1;
pPage->apCell[i] = pCell;
}else{
memcpy(&pPage->u.aDisk[idx], pCell, sz);
pPage->apCell[i] = (Cell*)&pPage->u.aDisk[idx];
}
}
/*
** Rebuild the linked list of cells on a page so that the cells
** occur in the order specified by the pPage->apCell[] array.
** Invoke this routine once to repair damage after one or more
** invocations of either insertCell() or dropCell().
*/
static void relinkCellList(MemPage *pPage){
int i;
u16 *pIdx;
assert( sqlitepager_iswriteable(pPage) );
pIdx = &pPage->u.hdr.firstCell;
for(i=0; i<pPage->nCell; i++){
int idx = Addr(pPage->apCell[i]) - Addr(pPage);
assert( idx>0 && idx<SQLITE_PAGE_SIZE );
*pIdx = idx;
pIdx = &pPage->apCell[i]->h.iNext;
}
*pIdx = 0;
}
/*
** Make a copy of the contents of pFrom into pTo. The pFrom->apCell[]
** pointers that point into pFrom->u.aDisk[] must be adjusted to point
** into pTo->u.aDisk[] instead. But some pFrom->apCell[] entries might
** not point to pFrom->u.aDisk[]. Those are unchanged.
*/
static void copyPage(MemPage *pTo, MemPage *pFrom){
uptr from, to;
int i;
memcpy(pTo->u.aDisk, pFrom->u.aDisk, SQLITE_PAGE_SIZE);
pTo->pParent = 0;
pTo->isInit = 1;
pTo->nCell = pFrom->nCell;
pTo->nFree = pFrom->nFree;
pTo->isOverfull = pFrom->isOverfull;
to = Addr(pTo);
from = Addr(pFrom);
for(i=0; i<pTo->nCell; i++){
uptr x = Addr(pFrom->apCell[i]);
if( x>from && x<from+SQLITE_PAGE_SIZE ){
*((uptr*)&pTo->apCell[i]) = x + to - from;
}else{
pTo->apCell[i] = pFrom->apCell[i];
}
}
}
/*
** This routine redistributes Cells on pPage and up to two siblings
** of pPage so that all pages have about the same amount of free space.
** Usually one sibling on either side of pPage is used in the balancing,
** though both siblings might come from one side if pPage is the first
** or last child of its parent. If pPage has fewer than two siblings
** (something which can only happen if pPage is the root page or a
** child of root) then all available siblings participate in the balancing.
**
** The number of siblings of pPage might be increased or decreased by
** one in an effort to keep pages between 66% and 100% full. The root page
** is special and is allowed to be less than 66% full. If pPage is
** the root page, then the depth of the tree might be increased
** or decreased by one, as necessary, to keep the root page from being
** overfull or empty.
**
** This routine calls relinkCellList() on its input page regardless of
** whether or not it does any real balancing. Client routines will typically
** invoke insertCell() or dropCell() before calling this routine, so we
** need to call relinkCellList() to clean up the mess that those other
** routines left behind.
**
** pCur is left pointing to the same cell as when this routine was called
** even if that cell gets moved to a different page. pCur may be NULL.
** Set the pCur parameter to NULL if you do not care about keeping track
** of a cell as that will save this routine the work of keeping track of it.
**
** Note that when this routine is called, some of the Cells on pPage
** might not actually be stored in pPage->u.aDisk[]. This can happen
** if the page is overfull. Part of the job of this routine is to
** make sure all Cells for pPage once again fit in pPage->u.aDisk[].
**
** In the course of balancing the siblings of pPage, the parent of pPage
** might become overfull or underfull. If that happens, then this routine
** is called recursively on the parent.
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state. So if this routine fails, the database should
** be rolled back.
*/
static int balance(Btree *pBt, MemPage *pPage, BtCursor *pCur){
MemPage *pParent; /* The parent of pPage */
MemPage *apOld[3]; /* pPage and up to two siblings */
Pgno pgnoOld[3]; /* Page numbers for each page in apOld[] */
MemPage *apNew[4]; /* pPage and up to 3 siblings after balancing */
Pgno pgnoNew[4]; /* Page numbers for each page in apNew[] */
int idxDiv[3]; /* Indices of divider cells in pParent */
Cell *apDiv[3]; /* Divider cells in pParent */
int nCell; /* Number of cells in apCell[] */
int nOld; /* Number of pages in apOld[] */
int nNew; /* Number of pages in apNew[] */
int nDiv; /* Number of cells in apDiv[] */
int i, j, k; /* Loop counters */
int idx; /* Index of pPage in pParent->apCell[] */
int nxDiv; /* Next divider slot in pParent->apCell[] */
int rc; /* The return code */
int iCur; /* apCell[iCur] is the cell of the cursor */
MemPage *pOldCurPage; /* The cursor originally points to this page */
int totalSize; /* Total bytes for all cells */
int subtotal; /* Subtotal of bytes in cells on one page */
int cntNew[4]; /* Index in apCell[] of cell after i-th page */
int szNew[4]; /* Combined size of cells place on i-th page */
MemPage *extraUnref = 0; /* A page that needs to be unref-ed */
Pgno pgno; /* Page number */
Cell *apCell[MX_CELL*3+5]; /* All cells from pages being balanceed */
int szCell[MX_CELL*3+5]; /* Local size of all cells */
Cell aTemp[2]; /* Temporary holding area for apDiv[] */
MemPage aOld[3]; /* Temporary copies of pPage and its siblings */
/*
** Return without doing any work if pPage is neither overfull nor
** underfull.
*/
assert( sqlitepager_iswriteable(pPage) );
if( !pPage->isOverfull && pPage->nFree<SQLITE_PAGE_SIZE/2
&& pPage->nCell>=2){
relinkCellList(pPage);
return SQLITE_OK;
}
/*
** Find the parent of the page to be balanceed.
** If there is no parent, it means this page is the root page and
** special rules apply.
*/
pParent = pPage->pParent;
if( pParent==0 ){
Pgno pgnoChild;
MemPage *pChild;
if( pPage->nCell==0 ){
if( pPage->u.hdr.rightChild ){
/*
** The root page is empty. Copy the one child page
** into the root page and return. This reduces the depth
** of the BTree by one.
*/
pgnoChild = pPage->u.hdr.rightChild;
rc = sqlitepager_get(pBt->pPager, pgnoChild, (void**)&pChild);
if( rc ) return rc;
memcpy(pPage, pChild, SQLITE_PAGE_SIZE);
pPage->isInit = 0;
rc = initPage(pPage, sqlitepager_pagenumber(pPage), 0);
assert( rc==SQLITE_OK );
reparentChildPages(pBt->pPager, pPage);
if( pCur && pCur->pPage==pChild ){
sqlitepager_unref(pChild);
pCur->pPage = pPage;
sqlitepager_ref(pPage);
}
freePage(pBt, pChild, pgnoChild);
sqlitepager_unref(pChild);
}else{
relinkCellList(pPage);
}
return SQLITE_OK;
}
if( !pPage->isOverfull ){
/* It is OK for the root page to be less than half full.
*/
relinkCellList(pPage);
return SQLITE_OK;
}
/*
** If we get to here, it means the root page is overfull.
** When this happens, Create a new child page and copy the
** contents of the root into the child. Then make the root
** page an empty page with rightChild pointing to the new
** child. Then fall thru to the code below which will cause
** the overfull child page to be split.
*/
rc = sqlitepager_write(pPage);
if( rc ) return rc;
rc = allocatePage(pBt, &pChild, &pgnoChild);
if( rc ) return rc;
assert( sqlitepager_iswriteable(pChild) );
copyPage(pChild, pPage);
pChild->pParent = pPage;
sqlitepager_ref(pPage);
pChild->isOverfull = 1;
if( pCur && pCur->pPage==pPage ){
sqlitepager_unref(pPage);
pCur->pPage = pChild;
}else{
extraUnref = pChild;
}
zeroPage(pPage);
pPage->u.hdr.rightChild = pgnoChild;
pParent = pPage;
pPage = pChild;
}
rc = sqlitepager_write(pParent);
if( rc ) return rc;
/*
** Find the Cell in the parent page whose h.leftChild points back
** to pPage. The "idx" variable is the index of that cell. If pPage
** is the rightmost child of pParent then set idx to pParent->nCell
*/
idx = -1;
pgno = sqlitepager_pagenumber(pPage);
for(i=0; i<pParent->nCell; i++){
if( pParent->apCell[i]->h.leftChild==pgno ){
idx = i;
break;
}
}
if( idx<0 && pParent->u.hdr.rightChild==pgno ){
idx = pParent->nCell;
}
if( idx<0 ){
return SQLITE_CORRUPT;
}
/*
** Initialize variables so that it will be safe to jump
** directly to balance_cleanup at any moment.
*/
nOld = nNew = 0;
sqlitepager_ref(pParent);
/*
** Find sibling pages to pPage and the Cells in pParent that divide
** the siblings. An attempt is made to find one sibling on either
** side of pPage. Both siblings are taken from one side, however, if
** pPage is either the first or last child of its parent. If pParent
** has 3 or fewer children then all children of pParent are taken.
*/
if( idx==pParent->nCell ){
nxDiv = idx - 2;
}else{
nxDiv = idx - 1;
}
if( nxDiv<0 ) nxDiv = 0;
nDiv = 0;
for(i=0, k=nxDiv; i<3; i++, k++){
if( k<pParent->nCell ){
idxDiv[i] = k;
apDiv[i] = pParent->apCell[k];
nDiv++;
pgnoOld[i] = apDiv[i]->h.leftChild;
}else if( k==pParent->nCell ){
pgnoOld[i] = pParent->u.hdr.rightChild;
}else{
break;
}
rc = sqlitepager_get(pBt->pPager, pgnoOld[i], (void**)&apOld[i]);
if( rc ) goto balance_cleanup;
rc = initPage(apOld[i], pgnoOld[i], pParent);
if( rc ) goto balance_cleanup;
nOld++;
}
/*
** Set iCur to be the index in apCell[] of the cell that the cursor
** is pointing to. We will need this later on in order to keep the
** cursor pointing at the same cell. If pCur points to a page that
** has no involvement with this rebalancing, then set iCur to a large
** number so that the iCur==j tests always fail in the main cell
** distribution loop below.
*/
if( pCur ){
iCur = 0;
for(i=0; i<nOld; i++){
if( pCur->pPage==apOld[i] ){
iCur += pCur->idx;
break;
}
iCur += apOld[i]->nCell;
if( i<nOld-1 && pCur->pPage==pParent && pCur->idx==idxDiv[i] ){
break;
}
iCur++;
}
pOldCurPage = pCur->pPage;
}
/*
** Make copies of the content of pPage and its siblings into aOld[].
** The rest of this function will use data from the copies rather
** that the original pages since the original pages will be in the
** process of being overwritten.
*/
for(i=0; i<nOld; i++){
copyPage(&aOld[i], apOld[i]);
rc = freePage(pBt, apOld[i], pgnoOld[i]);
if( rc ) goto balance_cleanup;
sqlitepager_unref(apOld[i]);
apOld[i] = &aOld[i];
}
/*
** Load pointers to all cells on sibling pages and the divider cells
** into the local apCell[] array. Make copies of the divider cells
** into aTemp[] and remove the the divider Cells from pParent.
*/
nCell = 0;
for(i=0; i<nOld; i++){
MemPage *pOld = apOld[i];
for(j=0; j<pOld->nCell; j++){
apCell[nCell] = pOld->apCell[j];
szCell[nCell] = cellSize(apCell[nCell]);
nCell++;
}
if( i<nOld-1 ){
szCell[nCell] = cellSize(apDiv[i]);
memcpy(&aTemp[i], apDiv[i], szCell[nCell]);
apCell[nCell] = &aTemp[i];
dropCell(pParent, nxDiv, szCell[nCell]);
assert( apCell[nCell]->h.leftChild==pgnoOld[i] );
apCell[nCell]->h.leftChild = pOld->u.hdr.rightChild;
nCell++;
}
}
/*
** Figure out the number of pages needed to hold all nCell cells.
** Store this number in "k". Also compute szNew[] which is the total
** size of all cells on the i-th page and cntNew[] which is the index
** in apCell[] of the cell that divides path i from path i+1.
** cntNew[k] should equal nCell.
**
** This little patch of code is critical for keeping the tree
** balanced.
*/
totalSize = 0;
for(i=0; i<nCell; i++){
totalSize += szCell[i];
}
for(subtotal=k=i=0; i<nCell; i++){
subtotal += szCell[i];
if( subtotal > USABLE_SPACE ){
szNew[k] = subtotal - szCell[i];
cntNew[k] = i;
subtotal = 0;
k++;
}
}
szNew[k] = subtotal;
cntNew[k] = nCell;
k++;
for(i=k-1; i>0; i--){
while( szNew[i]<USABLE_SPACE/2 ){
cntNew[i-1]--;
assert( cntNew[i-1]>0 );
szNew[i] += szCell[cntNew[i-1]];
szNew[i-1] -= szCell[cntNew[i-1]-1];
}
}
assert( cntNew[0]>0 );
/*
** Allocate k new pages
*/
for(i=0; i<k; i++){
rc = allocatePage(pBt, &apNew[i], &pgnoNew[i]);
if( rc ) goto balance_cleanup;
nNew++;
zeroPage(apNew[i]);
apNew[i]->isInit = 1;
}
/*
** Put the new pages in accending order. This helps to
** keep entries in the disk file in order so that a scan
** of the table is a linear scan through the file. That
** in turn helps the operating system to deliver pages
** from the disk more rapidly.
**
** An O(n^2) insertion sort algorithm is used, but since
** n is never more than 3, that should not be a problem.
**
** This one optimization makes the database about 25%
** faster for large insertions and deletions.
*/
for(i=0; i<k-1; i++){
int minV = pgnoNew[i];
int minI = i;
for(j=i+1; j<k; j++){
if( pgnoNew[j]<minV ){
minI = j;
minV = pgnoNew[j];
}
}
if( minI>i ){
int t;
MemPage *pT;
t = pgnoNew[i];
pT = apNew[i];
pgnoNew[i] = pgnoNew[minI];
apNew[i] = apNew[minI];
pgnoNew[minI] = t;
apNew[minI] = pT;
}
}
/*
** Evenly distribute the data in apCell[] across the new pages.
** Insert divider cells into pParent as necessary.
*/
j = 0;
for(i=0; i<nNew; i++){
MemPage *pNew = apNew[i];
while( j<cntNew[i] ){
assert( pNew->nFree>=szCell[j] );
if( pCur && iCur==j ){ pCur->pPage = pNew; pCur->idx = pNew->nCell; }
insertCell(pNew, pNew->nCell, apCell[j], szCell[j]);
j++;
}
assert( pNew->nCell>0 );
assert( !pNew->isOverfull );
relinkCellList(pNew);
if( i<nNew-1 && j<nCell ){
pNew->u.hdr.rightChild = apCell[j]->h.leftChild;
apCell[j]->h.leftChild = pgnoNew[i];
if( pCur && iCur==j ){ pCur->pPage = pParent; pCur->idx = nxDiv; }
insertCell(pParent, nxDiv, apCell[j], szCell[j]);
j++;
nxDiv++;
}
}
assert( j==nCell );
apNew[nNew-1]->u.hdr.rightChild = apOld[nOld-1]->u.hdr.rightChild;
if( nxDiv==pParent->nCell ){
pParent->u.hdr.rightChild = pgnoNew[nNew-1];
}else{
pParent->apCell[nxDiv]->h.leftChild = pgnoNew[nNew-1];
}
if( pCur ){
if( j<=iCur && pCur->pPage==pParent && pCur->idx>idxDiv[nOld-1] ){
assert( pCur->pPage==pOldCurPage );
pCur->idx += nNew - nOld;
}else{
assert( pOldCurPage!=0 );
sqlitepager_ref(pCur->pPage);
sqlitepager_unref(pOldCurPage);
}
}
/*
** Reparent children of all cells.
*/
for(i=0; i<nNew; i++){
reparentChildPages(pBt->pPager, apNew[i]);
}
reparentChildPages(pBt->pPager, pParent);
/*
** balance the parent page.
*/
rc = balance(pBt, pParent, pCur);
/*
** Cleanup before returning.
*/
balance_cleanup:
if( extraUnref ){
sqlitepager_unref(extraUnref);
}
for(i=0; i<nOld; i++){
if( apOld[i]!=&aOld[i] ) sqlitepager_unref(apOld[i]);
}
for(i=0; i<nNew; i++){
sqlitepager_unref(apNew[i]);
}
if( pCur && pCur->pPage==0 ){
pCur->pPage = pParent;
pCur->idx = 0;
}else{
sqlitepager_unref(pParent);
}
return rc;
}
/*
** Insert a new record into the BTree. The key is given by (pKey,nKey)
** and the data is given by (pData,nData). The cursor is used only to
** define what database the record should be inserted into. The cursor
** is left pointing at the new record.
*/
int sqliteBtreeInsert(
BtCursor *pCur, /* Insert data into the table of this cursor */
const void *pKey, int nKey, /* The key of the new record */
const void *pData, int nData /* The data of the new record */
){
Cell newCell;
int rc;
int loc;
int szNew;
MemPage *pPage;
Btree *pBt = pCur->pBt;
if( pCur->pPage==0 ){
return SQLITE_ABORT; /* A rollback destroyed this cursor */
}
if( !pCur->pBt->inTrans || nKey+nData==0 ){
return SQLITE_ERROR; /* Must start a transaction first */
}
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Cursor not open for writing */
}
rc = sqliteBtreeMoveto(pCur, pKey, nKey, &loc);
if( rc ) return rc;
pPage = pCur->pPage;
rc = sqlitepager_write(pPage);
if( rc ) return rc;
rc = fillInCell(pBt, &newCell, pKey, nKey, pData, nData);
if( rc ) return rc;
szNew = cellSize(&newCell);
if( loc==0 ){
newCell.h.leftChild = pPage->apCell[pCur->idx]->h.leftChild;
rc = clearCell(pBt, pPage->apCell[pCur->idx]);
if( rc ) return rc;
dropCell(pPage, pCur->idx, cellSize(pPage->apCell[pCur->idx]));
}else if( loc<0 && pPage->nCell>0 ){
assert( pPage->u.hdr.rightChild==0 ); /* Must be a leaf page */
pCur->idx++;
}else{
assert( pPage->u.hdr.rightChild==0 ); /* Must be a leaf page */
}
insertCell(pPage, pCur->idx, &newCell, szNew);
rc = balance(pCur->pBt, pPage, pCur);
/* sqliteBtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */
/* fflush(stdout); */
return rc;
}
/*
** Delete the entry that the cursor is pointing to.
**
** The cursor is left pointing at either the next or the previous
** entry. If the cursor is left pointing to the next entry, then
** the pCur->bSkipNext flag is set which forces the next call to
** sqliteBtreeNext() to be a no-op. That way, you can always call
** sqliteBtreeNext() after a delete and the cursor will be left
** pointing to the first entry after the deleted entry.
*/
int sqliteBtreeDelete(BtCursor *pCur){
MemPage *pPage = pCur->pPage;
Cell *pCell;
int rc;
Pgno pgnoChild;
if( pCur->pPage==0 ){
return SQLITE_ABORT; /* A rollback destroyed this cursor */
}
if( !pCur->pBt->inTrans ){
return SQLITE_ERROR; /* Must start a transaction first */
}
if( pCur->idx >= pPage->nCell ){
return SQLITE_ERROR; /* The cursor is not pointing to anything */
}
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Did not open this cursor for writing */
}
rc = sqlitepager_write(pPage);
if( rc ) return rc;
pCell = pPage->apCell[pCur->idx];
pgnoChild = pCell->h.leftChild;
clearCell(pCur->pBt, pCell);
if( pgnoChild ){
/*
** The entry we are about to delete is not a leaf so if we do not
** do something we will leave a hole on an internal page.
** We have to fill the hole by moving in a cell from a leaf. The
** next Cell after the one to be deleted is guaranteed to exist and
** to be a leaf so we can use it.
*/
BtCursor leafCur;
Cell *pNext;
int szNext;
getTempCursor(pCur, &leafCur);
rc = sqliteBtreeNext(&leafCur, 0);
if( rc!=SQLITE_OK ){
return SQLITE_CORRUPT;
}
rc = sqlitepager_write(leafCur.pPage);
if( rc ) return rc;
dropCell(pPage, pCur->idx, cellSize(pCell));
pNext = leafCur.pPage->apCell[leafCur.idx];
szNext = cellSize(pNext);
pNext->h.leftChild = pgnoChild;
insertCell(pPage, pCur->idx, pNext, szNext);
rc = balance(pCur->pBt, pPage, pCur);
if( rc ) return rc;
pCur->bSkipNext = 1;
dropCell(leafCur.pPage, leafCur.idx, szNext);
rc = balance(pCur->pBt, leafCur.pPage, pCur);
releaseTempCursor(&leafCur);
}else{
dropCell(pPage, pCur->idx, cellSize(pCell));
if( pCur->idx>=pPage->nCell ){
pCur->idx = pPage->nCell-1;
if( pCur->idx<0 ){
pCur->idx = 0;
pCur->bSkipNext = 1;
}else{
pCur->bSkipNext = 0;
}
}else{
pCur->bSkipNext = 1;
}
rc = balance(pCur->pBt, pPage, pCur);
}
return rc;
}
/*
** Create a new BTree table. Write into *piTable the page
** number for the root page of the new table.
**
** In the current implementation, BTree tables and BTree indices are the
** the same. But in the future, we may change this so that BTree tables
** are restricted to having a 4-byte integer key and arbitrary data and
** BTree indices are restricted to having an arbitrary key and no data.
*/
int sqliteBtreeCreateTable(Btree *pBt, int *piTable){
MemPage *pRoot;
Pgno pgnoRoot;
int rc;
if( !pBt->inTrans ){
return SQLITE_ERROR; /* Must start a transaction first */
}
if( pBt->readOnly ){
return SQLITE_READONLY;
}
rc = allocatePage(pBt, &pRoot, &pgnoRoot);
if( rc ) return rc;
assert( sqlitepager_iswriteable(pRoot) );
zeroPage(pRoot);
sqlitepager_unref(pRoot);
*piTable = (int)pgnoRoot;
return SQLITE_OK;
}
/*
** Create a new BTree index. Write into *piTable the page
** number for the root page of the new index.
**
** In the current implementation, BTree tables and BTree indices are the
** the same. But in the future, we may change this so that BTree tables
** are restricted to having a 4-byte integer key and arbitrary data and
** BTree indices are restricted to having an arbitrary key and no data.
*/
int sqliteBtreeCreateIndex(Btree *pBt, int *piIndex){
return sqliteBtreeCreateTable(pBt, piIndex);
}
/*
** Erase the given database page and all its children. Return
** the page to the freelist.
*/
static int clearDatabasePage(Btree *pBt, Pgno pgno, int freePageFlag){
MemPage *pPage;
int rc;
Cell *pCell;
int idx;
rc = sqlitepager_get(pBt->pPager, pgno, (void**)&pPage);
if( rc ) return rc;
rc = sqlitepager_write(pPage);
if( rc ) return rc;
idx = pPage->u.hdr.firstCell;
while( idx>0 ){
pCell = (Cell*)&pPage->u.aDisk[idx];
idx = pCell->h.iNext;
if( pCell->h.leftChild ){
rc = clearDatabasePage(pBt, pCell->h.leftChild, 1);
if( rc ) return rc;
}
rc = clearCell(pBt, pCell);
if( rc ) return rc;
}
if( pPage->u.hdr.rightChild ){
rc = clearDatabasePage(pBt, pPage->u.hdr.rightChild, 1);
if( rc ) return rc;
}
if( freePageFlag ){
rc = freePage(pBt, pPage, pgno);
}else{
zeroPage(pPage);
}
sqlitepager_unref(pPage);
return rc;
}
/*
** Delete all information from a single table in the database.
*/
int sqliteBtreeClearTable(Btree *pBt, int iTable){
int rc;
ptr nLock;
if( !pBt->inTrans ){
return SQLITE_ERROR; /* Must start a transaction first */
}
if( pBt->readOnly ){
return SQLITE_READONLY;
}
nLock = (ptr)sqliteHashFind(&pBt->locks, 0, iTable);
if( nLock ){
return SQLITE_LOCKED;
}
rc = clearDatabasePage(pBt, (Pgno)iTable, 0);
if( rc ){
sqliteBtreeRollback(pBt);
}
return rc;
}
/*
** Erase all information in a table and add the root of the table to
** the freelist. Except, the root of the principle table (the one on
** page 2) is never added to the freelist.
*/
int sqliteBtreeDropTable(Btree *pBt, int iTable){
int rc;
MemPage *pPage;
if( !pBt->inTrans ){
return SQLITE_ERROR; /* Must start a transaction first */
}
if( pBt->readOnly ){
return SQLITE_READONLY;
}
rc = sqlitepager_get(pBt->pPager, (Pgno)iTable, (void**)&pPage);
if( rc ) return rc;
rc = sqliteBtreeClearTable(pBt, iTable);
if( rc ) return rc;
if( iTable>2 ){
rc = freePage(pBt, pPage, iTable);
}else{
zeroPage(pPage);
}
sqlitepager_unref(pPage);
return rc;
}
/*
** Read the meta-information out of a database file.
*/
int sqliteBtreeGetMeta(Btree *pBt, int *aMeta){
PageOne *pP1;
int rc;
rc = sqlitepager_get(pBt->pPager, 1, (void**)&pP1);
if( rc ) return rc;
aMeta[0] = pP1->nFree;
memcpy(&aMeta[1], pP1->aMeta, sizeof(pP1->aMeta));
sqlitepager_unref(pP1);
return SQLITE_OK;
}
/*
** Write meta-information back into the database.
*/
int sqliteBtreeUpdateMeta(Btree *pBt, int *aMeta){
PageOne *pP1;
int rc;
if( !pBt->inTrans ){
return SQLITE_ERROR; /* Must start a transaction first */
}
if( pBt->readOnly ){
return SQLITE_READONLY;
}
pP1 = pBt->page1;
rc = sqlitepager_write(pP1);
if( rc ) return rc;
memcpy(pP1->aMeta, &aMeta[1], sizeof(pP1->aMeta));
return SQLITE_OK;
}
/******************************************************************************
** The complete implementation of the BTree subsystem is above this line.
** All the code the follows is for testing and troubleshooting the BTree
** subsystem. None of the code that follows is used during normal operation.
******************************************************************************/
/*
** Print a disassembly of the given page on standard output. This routine
** is used for debugging and testing only.
*/
#ifdef SQLITE_TEST
int sqliteBtreePageDump(Btree *pBt, int pgno, int recursive){
int rc;
MemPage *pPage;
int i, j;
int nFree;
u16 idx;
char range[20];
unsigned char payload[20];
rc = sqlitepager_get(pBt->pPager, (Pgno)pgno, (void**)&pPage);
if( rc ){
return rc;
}
if( recursive ) printf("PAGE %d:\n", pgno);
i = 0;
idx = pPage->u.hdr.firstCell;
while( idx>0 && idx<=SQLITE_PAGE_SIZE-MIN_CELL_SIZE ){
Cell *pCell = (Cell*)&pPage->u.aDisk[idx];
int sz = cellSize(pCell);
sprintf(range,"%d..%d", idx, idx+sz-1);
sz = NKEY(pCell->h) + NDATA(pCell->h);
if( sz>sizeof(payload)-1 ) sz = sizeof(payload)-1;
memcpy(payload, pCell->aPayload, sz);
for(j=0; j<sz; j++){
if( payload[j]<0x20 || payload[j]>0x7f ) payload[j] = '.';
}
payload[sz] = 0;
printf(
"cell %2d: i=%-10s chld=%-4d nk=%-4d nd=%-4d payload=%s\n",
i, range, (int)pCell->h.leftChild, NKEY(pCell->h), NDATA(pCell->h),
payload
);
if( pPage->isInit && pPage->apCell[i]!=pCell ){
printf("**** apCell[%d] does not match on prior entry ****\n", i);
}
i++;
idx = pCell->h.iNext;
}
if( idx!=0 ){
printf("ERROR: next cell index out of range: %d\n", idx);
}
printf("right_child: %d\n", pPage->u.hdr.rightChild);
nFree = 0;
i = 0;
idx = pPage->u.hdr.firstFree;
while( idx>0 && idx<SQLITE_PAGE_SIZE ){
FreeBlk *p = (FreeBlk*)&pPage->u.aDisk[idx];
sprintf(range,"%d..%d", idx, idx+p->iSize-1);
nFree += p->iSize;
printf("freeblock %2d: i=%-10s size=%-4d total=%d\n",
i, range, p->iSize, nFree);
idx = p->iNext;
i++;
}
if( idx!=0 ){
printf("ERROR: next freeblock index out of range: %d\n", idx);
}
if( recursive && pPage->u.hdr.rightChild!=0 ){
idx = pPage->u.hdr.firstCell;
while( idx>0 && idx<SQLITE_PAGE_SIZE-MIN_CELL_SIZE ){
Cell *pCell = (Cell*)&pPage->u.aDisk[idx];
sqliteBtreePageDump(pBt, pCell->h.leftChild, 1);
idx = pCell->h.iNext;
}
sqliteBtreePageDump(pBt, pPage->u.hdr.rightChild, 1);
}
sqlitepager_unref(pPage);
return SQLITE_OK;
}
#endif
#ifdef SQLITE_TEST
/*
** Fill aResult[] with information about the entry and page that the
** cursor is pointing to.
**
** aResult[0] = The page number
** aResult[1] = The entry number
** aResult[2] = Total number of entries on this page
** aResult[3] = Size of this entry
** aResult[4] = Number of free bytes on this page
** aResult[5] = Number of free blocks on the page
** aResult[6] = Page number of the left child of this entry
** aResult[7] = Page number of the right child for the whole page
**
** This routine is used for testing and debugging only.
*/
int sqliteBtreeCursorDump(BtCursor *pCur, int *aResult){
int cnt, idx;
MemPage *pPage = pCur->pPage;
aResult[0] = sqlitepager_pagenumber(pPage);
aResult[1] = pCur->idx;
aResult[2] = pPage->nCell;
if( pCur->idx>=0 && pCur->idx<pPage->nCell ){
aResult[3] = cellSize(pPage->apCell[pCur->idx]);
aResult[6] = pPage->apCell[pCur->idx]->h.leftChild;
}else{
aResult[3] = 0;
aResult[6] = 0;
}
aResult[4] = pPage->nFree;
cnt = 0;
idx = pPage->u.hdr.firstFree;
while( idx>0 && idx<SQLITE_PAGE_SIZE ){
cnt++;
idx = ((FreeBlk*)&pPage->u.aDisk[idx])->iNext;
}
aResult[5] = cnt;
aResult[7] = pPage->u.hdr.rightChild;
return SQLITE_OK;
}
#endif
#ifdef SQLITE_TEST
/*
** Return the pager associated with a BTree. This routine is used for
** testing and debugging only.
*/
Pager *sqliteBtreePager(Btree *pBt){
return pBt->pPager;
}
#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 {
Btree *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 nTreePage; /* Number of BTree pages */
int nByte; /* Number of bytes of data stored on BTree pages */
char *zErrMsg; /* An error message. NULL of no errors seen. */
};
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(IntegrityCk *pCheck, char *zMsg1, char *zMsg2){
if( pCheck->zErrMsg ){
char *zOld = pCheck->zErrMsg;
pCheck->zErrMsg = 0;
sqliteSetString(&pCheck->zErrMsg, zOld, "\n", zMsg1, zMsg2, 0);
sqliteFree(zOld);
}else{
sqliteSetString(&pCheck->zErrMsg, zMsg1, zMsg2, 0);
}
}
/*
** Add 1 to the reference count for page iPage. If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 ore more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, int iPage, char *zContext){
if( iPage==0 ) return 1;
if( iPage>pCheck->nPage ){
char zBuf[100];
sprintf(zBuf, "invalid page number %d", iPage);
checkAppendMsg(pCheck, zContext, zBuf);
return 1;
}
if( pCheck->anRef[iPage]==1 ){
char zBuf[100];
sprintf(zBuf, "2nd reference to page %d", iPage);
checkAppendMsg(pCheck, zContext, zBuf);
return 1;
}
return (pCheck->anRef[iPage]++)>1;
}
/*
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
IntegrityCk *pCheck, /* Integrity checking context */
int isFreeList, /* True for a freelist. False for overflow page list */
int iPage, /* Page number for first page in the list */
int N, /* Expected number of pages in the list */
char *zContext /* Context for error messages */
){
int i;
char zMsg[100];
while( N-- > 0 ){
OverflowPage *pOvfl;
if( iPage<1 ){
sprintf(zMsg, "%d pages missing from overflow list", N+1);
checkAppendMsg(pCheck, zContext, zMsg);
break;
}
if( checkRef(pCheck, iPage, zContext) ) break;
if( sqlitepager_get(pCheck->pPager, (Pgno)iPage, (void**)&pOvfl) ){
sprintf(zMsg, "failed to get page %d", iPage);
checkAppendMsg(pCheck, zContext, zMsg);
break;
}
if( isFreeList ){
FreelistInfo *pInfo = (FreelistInfo*)pOvfl->aPayload;
for(i=0; i<pInfo->nFree; i++){
checkRef(pCheck, pInfo->aFree[i], zMsg);
}
N -= pInfo->nFree;
}
iPage = (int)pOvfl->iNext;
sqlitepager_unref(pOvfl);
}
}
/*
** Return negative if zKey1<zKey2.
** Return zero if zKey1==zKey2.
** Return positive if zKey1>zKey2.
*/
static int keyCompare(
const char *zKey1, int nKey1,
const char *zKey2, int nKey2
){
int min = nKey1>nKey2 ? nKey2 : nKey1;
int c = memcmp(zKey1, zKey2, min);
if( c==0 ){
c = nKey1 - nKey2;
}
return c;
}
/*
** Do various sanity checks on a single page of a tree. Return
** the tree depth. Root pages return 0. Parents of root pages
** return 1, and so forth.
**
** These checks are done:
**
** 1. Make sure that cells and freeblocks do not overlap
** but combine to completely cover the page.
** 2. Make sure cell keys are in order.
** 3. Make sure no key is less than or equal to zLowerBound.
** 4. Make sure no key is greater than or equal to zUpperBound.
** 5. Check the integrity of overflow pages.
** 6. Recursively call checkTreePage on all children.
** 7. Verify that the depth of all children is the same.
** 8. Make sure this page is at least 33% full or else it is
** the root of the tree.
*/
static int checkTreePage(
IntegrityCk *pCheck, /* Context for the sanity check */
int iPage, /* Page number of the page to check */
MemPage *pParent, /* Parent page */
char *zParentContext, /* Parent context */
char *zLowerBound, /* All keys should be greater than this, if not NULL */
int nLower, /* Number of characters in zLowerBound */
char *zUpperBound, /* All keys should be less than this, if not NULL */
int nUpper /* Number of characters in zUpperBound */
){
MemPage *pPage;
int i, rc, depth, d2, pgno;
char *zKey1, *zKey2;
int nKey1, nKey2;
BtCursor cur;
char zMsg[100];
char zContext[100];
char hit[SQLITE_PAGE_SIZE];
/* Check that the page exists
*/
if( iPage==0 ) return 0;
if( checkRef(pCheck, iPage, zParentContext) ) return 0;
sprintf(zContext, "On tree page %d: ", iPage);
if( (rc = sqlitepager_get(pCheck->pPager, (Pgno)iPage, (void**)&pPage))!=0 ){
sprintf(zMsg, "unable to get the page. error code=%d", rc);
checkAppendMsg(pCheck, zContext, zMsg);
return 0;
}
if( (rc = initPage(pPage, (Pgno)iPage, pParent))!=0 ){
sprintf(zMsg, "initPage() returns error code %d", rc);
checkAppendMsg(pCheck, zContext, zMsg);
sqlitepager_unref(pPage);
return 0;
}
/* Check out all the cells.
*/
depth = 0;
if( zLowerBound ){
zKey1 = sqliteMalloc( nLower+1 );
memcpy(zKey1, zLowerBound, nLower);
zKey1[nLower] = 0;
}else{
zKey1 = 0;
}
nKey1 = nLower;
cur.pPage = pPage;
cur.pBt = pCheck->pBt;
for(i=0; i<pPage->nCell; i++){
Cell *pCell = pPage->apCell[i];
int sz;
/* Check payload overflow pages
*/
nKey2 = NKEY(pCell->h);
sz = nKey2 + NDATA(pCell->h);
sprintf(zContext, "On page %d cell %d: ", iPage, i);
if( sz>MX_LOCAL_PAYLOAD ){
int nPage = (sz - MX_LOCAL_PAYLOAD + OVERFLOW_SIZE - 1)/OVERFLOW_SIZE;
checkList(pCheck, 0, pCell->ovfl, nPage, zContext);
}
/* Check that keys are in the right order
*/
cur.idx = i;
zKey2 = sqliteMalloc( nKey2+1 );
getPayload(&cur, 0, nKey2, zKey2);
if( zKey1 && keyCompare(zKey1, nKey1, zKey2, nKey2)>=0 ){
checkAppendMsg(pCheck, zContext, "Key is out of order");
}
/* Check sanity of left child page.
*/
pgno = (int)pCell->h.leftChild;
d2 = checkTreePage(pCheck, pgno, pPage, zContext, zKey1,nKey1,zKey2,nKey2);
if( i>0 && d2!=depth ){
checkAppendMsg(pCheck, zContext, "Child page depth differs");
}
depth = d2;
sqliteFree(zKey1);
zKey1 = zKey2;
nKey1 = nKey2;
}
pgno = pPage->u.hdr.rightChild;
sprintf(zContext, "On page %d at right child: ", iPage);
checkTreePage(pCheck, pgno, pPage, zContext, zKey1,nKey1,zUpperBound,nUpper);
sqliteFree(zKey1);
/* Check for complete coverage of the page
*/
memset(hit, 0, sizeof(hit));
memset(hit, 1, sizeof(PageHdr));
for(i=pPage->u.hdr.firstCell; i>0 && i<SQLITE_PAGE_SIZE; ){
Cell *pCell = (Cell*)&pPage->u.aDisk[i];
int j;
for(j=i+cellSize(pCell)-1; j>=i; j--) hit[j]++;
i = pCell->h.iNext;
}
for(i=pPage->u.hdr.firstFree; i>0 && i<SQLITE_PAGE_SIZE; ){
FreeBlk *pFBlk = (FreeBlk*)&pPage->u.aDisk[i];
int j;
for(j=i+pFBlk->iSize-1; j>=i; j--) hit[j]++;
i = pFBlk->iNext;
}
for(i=0; i<SQLITE_PAGE_SIZE; i++){
if( hit[i]==0 ){
sprintf(zMsg, "Unused space at byte %d of page %d", i, iPage);
checkAppendMsg(pCheck, zMsg, 0);
break;
}else if( hit[i]>1 ){
sprintf(zMsg, "Multiple uses for byte %d of page %d", i, iPage);
checkAppendMsg(pCheck, zMsg, 0);
break;
}
}
/* Check that free space is kept to a minimum
*/
#if 0
if( pParent && pParent->nCell>2 && pPage->nFree>3*SQLITE_PAGE_SIZE/4 ){
sprintf(zMsg, "free space (%d) greater than max (%d)", pPage->nFree,
SQLITE_PAGE_SIZE/3);
checkAppendMsg(pCheck, zContext, zMsg);
}
#endif
/* Update freespace totals.
*/
pCheck->nTreePage++;
pCheck->nByte += USABLE_SPACE - pPage->nFree;
sqlitepager_unref(pPage);
return depth;
}
/*
** This routine does a complete check of the given BTree file. aRoot[] is
** an array of pages numbers were each page number is the root page of
** a table. nRoot is the number of entries in aRoot.
**
** If everything checks out, this routine returns NULL. If something is
** amiss, an error message is written into memory obtained from malloc()
** and a pointer to that error message is returned. The calling function
** is responsible for freeing the error message when it is done.
*/
char *sqliteBtreeIntegrityCheck(Btree *pBt, int *aRoot, int nRoot){
int i;
int nRef;
IntegrityCk sCheck;
nRef = *sqlitepager_stats(pBt->pPager);
if( lockBtree(pBt)!=SQLITE_OK ){
return sqliteStrDup("Unable to acquire a read lock on the database");
}
sCheck.pBt = pBt;
sCheck.pPager = pBt->pPager;
sCheck.nPage = sqlitepager_pagecount(sCheck.pPager);
sCheck.anRef = sqliteMalloc( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
sCheck.anRef[1] = 1;
for(i=2; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
sCheck.zErrMsg = 0;
/* Check the integrity of the freelist
*/
checkList(&sCheck, 1, pBt->page1->freeList, pBt->page1->nFree,
"Main freelist: ");
/* Check all the tables.
*/
for(i=0; i<nRoot; i++){
if( aRoot[i]==0 ) continue;
checkTreePage(&sCheck, aRoot[i], 0, "List of tree roots: ", 0,0,0,0);
}
/* Make sure every page in the file is referenced
*/
for(i=1; i<=sCheck.nPage; i++){
if( sCheck.anRef[i]==0 ){
char zBuf[100];
sprintf(zBuf, "Page %d is never used", i);
checkAppendMsg(&sCheck, zBuf, 0);
}
}
/* Make sure this analysis did not leave any unref() pages
*/
unlockBtreeIfUnused(pBt);
if( nRef != *sqlitepager_stats(pBt->pPager) ){
char zBuf[100];
sprintf(zBuf,
"Outstanding page count goes from %d to %d during this analysis",
nRef, *sqlitepager_stats(pBt->pPager)
);
checkAppendMsg(&sCheck, zBuf, 0);
}
/* Clean up and report errors.
*/
sqliteFree(sCheck.anRef);
return sCheck.zErrMsg;
}