SQLite

  aNew = &db->aDb[db->nDb];
  memset(aNew, 0, sizeof(*aNew));

  /* Open the database file. If the btree is successfully opened, use
  ** it to obtain the database schema. At this point the schema may
  ** or may not be initialised.
  */
  rc = sqlite3BtreeFactory(db, zFile, 0, SQLITE_DEFAULT_CACHE_SIZE,
                           db->openFlags | SQLITE_OPEN_MAIN_DB,
                           &aNew->pBt);
  db->nDb++;
  if( rc==SQLITE_CONSTRAINT ){
    rc = SQLITE_ERROR;
    zErrDyn = sqlite3MPrintf(db, "database is already attached");
  }else if( rc==SQLITE_OK ){
    Pager *pPager;
    aNew->pSchema = sqlite3SchemaGet(db, aNew->pBt);

  return sqlite3InvokeBusyHandler(&pBt->db->busyHandler);
}

/*
** Open a database file.
** 
** 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 sqlite3BtreeClose() is called.

** If zFilename is ":memory:" then an in-memory database is created
** that is automatically destroyed when it is closed.
**






** If the database is already opened in the same database connection
** and we are in shared cache mode, then the open will fail with an
** SQLITE_CONSTRAINT error.  We cannot allow two or more BtShared
** objects in the same database connection since doing so will lead
** to problems with locking.
*/
int sqlite3BtreeOpen(
  const char *zFilename,  /* Name of the file containing the BTree database */
  sqlite3 *db,            /* Associated database handle */
  Btree **ppBtree,        /* Pointer to new Btree object written here */
  int flags,              /* Options */
  int vfsFlags            /* Flags passed through to sqlite3_vfs.xOpen() */
){
  sqlite3_vfs *pVfs;             /* The VFS to use for this btree */
  BtShared *pBt = 0;             /* Shared part of btree structure */
  Btree *p;                      /* Handle to return */
  sqlite3_mutex *mutexOpen = 0;  /* Prevents a race condition. Ticket #3537 */
  int rc = SQLITE_OK;            /* Result code from this function */
  u8 nReserve;                   /* Byte of unused space on each page */
  unsigned char zDbHeader[100];  /* Database header content */




  /* Set the variable isMemdb to true for an in-memory database, or 
  ** false for a file-based database. This symbol is only required if
  ** either of the shared-data or autovacuum features are compiled 
  ** into the library.
  */
#if !defined(SQLITE_OMIT_SHARED_CACHE) || !defined(SQLITE_OMIT_AUTOVACUUM)
  #ifdef SQLITE_OMIT_MEMORYDB
    const int isMemdb = 0;
  #else
    const int isMemdb = zFilename && !strcmp(zFilename, ":memory:");

  #endif
#endif

  assert( db!=0 );
  assert( sqlite3_mutex_held(db->mutex) );










  pVfs = db->pVfs;
  p = sqlite3MallocZero(sizeof(Btree));
  if( !p ){
    return SQLITE_NOMEM;
  }
  p->inTrans = TRANS_NONE;
  p->db = db;
#ifndef SQLITE_OMIT_SHARED_CACHE
  p->lock.pBtree = p;
  p->lock.iTable = 1;
#endif

#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
  /*
  ** If this Btree is a candidate for shared cache, try to find an
  ** existing BtShared object that we can share with
  */
  if( isMemdb==0 && zFilename && zFilename[0] ){
    if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
      int nFullPathname = pVfs->mxPathname+1;
      char *zFullPathname = sqlite3Malloc(nFullPathname);
      sqlite3_mutex *mutexShared;
      p->sharable = 1;
      if( !zFullPathname ){
        sqlite3_free(p);

  if( rc!=SQLITE_OK ){
    if( pBt && pBt->pPager ){
      sqlite3PagerClose(pBt->pPager);
    }
    sqlite3_free(pBt);
    sqlite3_free(p);
    *ppBtree = 0;








  }
  if( mutexOpen ){
    assert( sqlite3_mutex_held(mutexOpen) );
    sqlite3_mutex_leave(mutexOpen);
  }
  return rc;
}

    static const int flags = 
          SQLITE_OPEN_READWRITE |
          SQLITE_OPEN_CREATE |
          SQLITE_OPEN_EXCLUSIVE |
          SQLITE_OPEN_DELETEONCLOSE |
          SQLITE_OPEN_TEMP_DB;

    rc = sqlite3BtreeFactory(db, 0, 0, SQLITE_DEFAULT_CACHE_SIZE, flags, &pBt);
    if( rc!=SQLITE_OK ){
      sqlite3ErrorMsg(pParse, "unable to open a temporary database "
        "file for storing temporary tables");
      pParse->rc = rc;
      return 1;
    }
    db->aDb[1].pBt = pBt;

  return 1;
#endif
#if SQLITE_TEMP_STORE<1 || SQLITE_TEMP_STORE>3
  return 0;
#endif
}

/*
** This routine is called to create a connection to a database BTree
** driver.  If zFilename is the name of a file, then that file is
** opened and used.  If zFilename is the magic name ":memory:" then
** the database is stored in memory (and is thus forgotten as soon as
** the connection is closed.)  If zFilename is NULL then the database
** is a "virtual" database for transient use only and is deleted as
** soon as the connection is closed.
**
** A virtual database can be either a disk file (that is automatically
** deleted when the file is closed) or it an be held entirely in memory.
** The sqlite3TempInMemory() function is used to determine which.
*/
int sqlite3BtreeFactory(
  sqlite3 *db,              /* Main database when opening aux otherwise 0 */
  const char *zFilename,    /* Name of the file containing the BTree database */
  int omitJournal,          /* if TRUE then do not journal this file */
  int nCache,               /* How many pages in the page cache */
  int vfsFlags,             /* Flags passed through to vfsOpen */
  Btree **ppBtree           /* Pointer to new Btree object written here */
){
  int btFlags = 0;
  int rc;
  
  assert( sqlite3_mutex_held(db->mutex) );
  assert( ppBtree != 0);
  if( omitJournal ){
    btFlags |= BTREE_OMIT_JOURNAL;
  }
  if( db->flags & SQLITE_NoReadlock ){
    btFlags |= BTREE_NO_READLOCK;
  }
#ifndef SQLITE_OMIT_MEMORYDB
  if( zFilename==0 && sqlite3TempInMemory(db) ){
    zFilename = ":memory:";
  }
#endif

  if( (vfsFlags & SQLITE_OPEN_MAIN_DB)!=0 && (zFilename==0 || *zFilename==0) ){
    vfsFlags = (vfsFlags & ~SQLITE_OPEN_MAIN_DB) | SQLITE_OPEN_TEMP_DB;
  }
  rc = sqlite3BtreeOpen(zFilename, (sqlite3 *)db, ppBtree, btFlags, vfsFlags);

  /* If the B-Tree was successfully opened, set the pager-cache size to the
  ** default value. Except, if the call to BtreeOpen() returned a handle
  ** open on an existing shared pager-cache, do not change the pager-cache 
  ** size.
  */
  if( rc==SQLITE_OK && 0==sqlite3BtreeSchema(*ppBtree, 0, 0) ){
    sqlite3BtreeSetCacheSize(*ppBtree, nCache);
  }
  return rc;
}

/*
** Return UTF-8 encoded English language explanation of the most recent
** error.
*/
const char *sqlite3_errmsg(sqlite3 *db){
  const char *z;
  if( !db ){

  /* Also add a UTF-8 case-insensitive collation sequence. */
  createCollation(db, "NOCASE", SQLITE_UTF8, SQLITE_COLL_NOCASE, 0,
                  nocaseCollatingFunc, 0);

  /* Open the backend database driver */
  db->openFlags = flags;
  rc = sqlite3BtreeFactory(db, zFilename, 0, SQLITE_DEFAULT_CACHE_SIZE, 
                           flags | SQLITE_OPEN_MAIN_DB,
                           &db->aDb[0].pBt);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_IOERR_NOMEM ){
      rc = SQLITE_NOMEM;
    }
    sqlite3Error(db, rc, 0);
    goto opendb_out;
  }

    journalFileSize = ROUND8(sqlite3JournalSize(pVfs));
  }else{
    journalFileSize = ROUND8(sqlite3MemJournalSize());
  }

  /* Set the output variable to NULL in case an error occurs. */
  *ppPager = 0;








  /* Compute and store the full pathname in an allocated buffer pointed
  ** to by zPathname, length nPathname. Or, if this is a temporary file,
  ** leave both nPathname and zPathname set to 0.
  */
  if( zFilename && zFilename[0] ){
    nPathname = pVfs->mxPathname+1;
    zPathname = sqlite3Malloc(nPathname*2);
    if( zPathname==0 ){
      return SQLITE_NOMEM;
    }
#ifndef SQLITE_OMIT_MEMORYDB
    if( strcmp(zFilename,":memory:")==0 ){
      memDb = 1;
      zPathname[0] = 0;
    }else
#endif
    {
      zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */
      rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
    }

    nPathname = sqlite3Strlen30(zPathname);
    if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
      /* This branch is taken when the journal path required by
      ** the database being opened will be more than pVfs->mxPathname
      ** bytes in length. This means the database cannot be opened,
      ** as it will not be possible to open the journal file or even
      ** check for a hot-journal before reading.

/*
** Allowed values for the flags parameter to sqlite3PagerOpen().
**
** NOTE: These values must match the corresponding BTREE_ values in btree.h.
*/
#define PAGER_OMIT_JOURNAL  0x0001    /* Do not use a rollback journal */
#define PAGER_NO_READLOCK   0x0002    /* Omit readlocks on readonly files */


/*
** Valid values for the second argument to sqlite3PagerLockingMode().
*/
#define PAGER_LOCKINGMODE_QUERY      -1
#define PAGER_LOCKINGMODE_NORMAL      0
#define PAGER_LOCKINGMODE_EXCLUSIVE   1

# define sqlite3AuthRead(a,b,c,d)
# define sqlite3AuthCheck(a,b,c,d,e)    SQLITE_OK
# define sqlite3AuthContextPush(a,b,c)
# define sqlite3AuthContextPop(a)  ((void)(a))
#endif
void sqlite3Attach(Parse*, Expr*, Expr*, Expr*);
void sqlite3Detach(Parse*, Expr*);
int sqlite3BtreeFactory(sqlite3 *db, const char *zFilename,
                       int omitJournal, int nCache, int flags, Btree **ppBtree);
int sqlite3FixInit(DbFixer*, Parse*, int, const char*, const Token*);
int sqlite3FixSrcList(DbFixer*, SrcList*);
int sqlite3FixSelect(DbFixer*, Select*);
int sqlite3FixExpr(DbFixer*, Expr*);
int sqlite3FixExprList(DbFixer*, ExprList*);
int sqlite3FixTriggerStep(DbFixer*, TriggerStep*);
int sqlite3AtoF(const char *z, double*);

** A bogus sqlite3 connection structure for use in the btree
** tests.
*/
static sqlite3 sDb;
static int nRefSqlite3 = 0;

/*
** Usage:   btree_open FILENAME NCACHE FLAGS
**
** Open a new database
*/
static int btree_open(
  void *NotUsed,
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int argc,              /* Number of arguments */
  const char **argv      /* Text of each argument */
){
  Btree *pBt;
  int rc, nCache, flags;
  char zBuf[100];
  if( argc!=4 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " FILENAME NCACHE FLAGS\"", 0);
    return TCL_ERROR;
  }
  if( Tcl_GetInt(interp, argv[2], &nCache) ) return TCL_ERROR;
  if( Tcl_GetInt(interp, argv[3], &flags) ) return TCL_ERROR;
  nRefSqlite3++;
  if( nRefSqlite3==1 ){
    sDb.pVfs = sqlite3_vfs_find(0);
    sDb.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
    sqlite3_mutex_enter(sDb.mutex);
  }
  rc = sqlite3BtreeOpen(argv[1], &sDb, &pBt, flags,
     SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB);
  if( rc!=SQLITE_OK ){
    Tcl_AppendResult(interp, errorName(rc), 0);
    return TCL_ERROR;
  }
  sqlite3BtreeSetCacheSize(pBt, nCache);
  sqlite3_snprintf(sizeof(zBuf), zBuf,"%p", pBt);

      SQLITE_OPEN_DELETEONCLOSE |
      SQLITE_OPEN_TRANSIENT_DB;

  assert( pOp->p1>=0 );
  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  rc = sqlite3BtreeFactory(db, 0, 1, SQLITE_DEFAULT_TEMP_CACHE_SIZE, openFlags,
                           &pCx->pBt);
  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeBeginTrans(pCx->pBt, 1);
  }
  if( rc==SQLITE_OK ){
    /* If a transient index is required, create it by calling
    ** sqlite3BtreeCreateTable() with the BTREE_ZERODATA flag before
    ** opening it. If a transient table is required, just use the

  DROP TABLE t1;
}

# Open the table with root-page $rootpage at the btree
# level. Return a list that is the length of each record
# in the table, in the tables default scanning order.
proc record_sizes {rootpage} {
  set bt [btree_open test.db 10 0]
  btree_begin_transaction $bt
  set c [btree_cursor $bt $rootpage 0]
  btree_first $c
  while 1 {
    lappend res [btree_payload_size $c]
    if {[btree_next $c]} break
  }