pNode->isDirty = 0;
  pNode->pNext = 0;

  sqlite3_bind_int64(pRtree->pReadNode, 1, iNode);
  rc = sqlite3_step(pRtree->pReadNode);
  if( rc==SQLITE_ROW ){
    const u8 *zBlob = sqlite3_column_blob(pRtree->pReadNode, 0);

    memcpy(pNode->zData, zBlob, pRtree->iNodeSize);
    nodeReference(pParent);
  }else{
    sqlite3_free(pNode);
    pNode = 0;
  }

................................................................................
    sqlite3_free(zSql);
  }

  return rc;
}

/*
** This routine queries database handle db for the page-size used by
** database zDb. If successful, the page-size in bytes is written to

** *piPageSize and SQLITE_OK returned. Otherwise, and an SQLite error 
** code is returned.
*/
static int getPageSize(sqlite3 *db, const char *zDb, int *piPageSize){
  int rc = SQLITE_NOMEM;
  char *zSql;
  sqlite3_stmt *pStmt = 0;





  zSql = sqlite3_mprintf("PRAGMA %Q.page_size", zDb);
  if( !zSql ){



    return SQLITE_NOMEM;
  }

  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
  sqlite3_free(zSql);


























  if( rc!=SQLITE_OK ){
    return rc;



  }

  if( SQLITE_ROW==sqlite3_step(pStmt) ){
    *piPageSize = sqlite3_column_int(pStmt, 0);






  }
  return sqlite3_finalize(pStmt);



}

/* 
** This function is the implementation of both the xConnect and xCreate
** methods of the r-tree virtual table.
**
**   argv[0]   -> module name
................................................................................

  int iErr = (argc<6) ? 2 : argc>(RTREE_MAX_DIMENSIONS*2+4) ? 3 : argc%2;
  if( aErrMsg[iErr] ){
    *pzErr = sqlite3_mprintf("%s", aErrMsg[iErr]);
    return SQLITE_ERROR;
  }

  rc = getPageSize(db, argv[1], &iPageSize);
  if( rc!=SQLITE_OK ){
    return rc;
  }

  /* Allocate the sqlite3_vtab structure */
  nDb = strlen(argv[1]);
  nName = strlen(argv[2]);
  pRtree = (Rtree *)sqlite3_malloc(sizeof(Rtree)+nDb+nName+2);
  if( !pRtree ){
    return SQLITE_NOMEM;
  }
................................................................................
  pRtree->zName = &pRtree->zDb[nDb+1];
  pRtree->nDim = (argc-4)/2;
  pRtree->nBytesPerCell = 8 + pRtree->nDim*4*2;
  pRtree->eCoordType = eCoordType;
  memcpy(pRtree->zDb, argv[1], nDb);
  memcpy(pRtree->zName, argv[2], nName);

  /* Figure out the node size to use. By default, use 64 bytes less than
  ** the database page-size. This ensures that each node is stored on
  ** a single database page.
  **
  ** If the databasd page-size is so large that more than RTREE_MAXCELLS
  ** entries would fit in a single node, use a smaller node-size.
  */
  pRtree->iNodeSize = iPageSize-64;
  if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
    pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
  }

  /* Create/Connect to the underlying relational database schema. If
  ** that is successful, call sqlite3_declare_vtab() to configure
  ** the r-tree table schema.
  */

  if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
    *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
  }else{
    char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
    char *zTmp;
    int ii;
    for(ii=4; zSql && ii<argc; ii++){
      zTmp = zSql;
      zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
      sqlite3_free(zTmp);
    }
    if( zSql ){
      zTmp = zSql;
      zSql = sqlite3_mprintf("%s);", zTmp);
      sqlite3_free(zTmp);
    }
    if( !zSql ){
      rc = SQLITE_NOMEM;
    }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
    }
    sqlite3_free(zSql);

  }

  if( rc==SQLITE_OK ){
    *ppVtab = (sqlite3_vtab *)pRtree;
  }else{
    rtreeRelease(pRtree);
  }

  pNode->isDirty = 0;
  pNode->pNext = 0;

  sqlite3_bind_int64(pRtree->pReadNode, 1, iNode);
  rc = sqlite3_step(pRtree->pReadNode);
  if( rc==SQLITE_ROW ){
    const u8 *zBlob = sqlite3_column_blob(pRtree->pReadNode, 0);
    assert( sqlite3_column_bytes(pRtree->pReadNode, 0)==pRtree->iNodeSize );
    memcpy(pNode->zData, zBlob, pRtree->iNodeSize);
    nodeReference(pParent);
  }else{
    sqlite3_free(pNode);
    pNode = 0;
  }

................................................................................
    sqlite3_free(zSql);
  }

  return rc;
}

/*
** The second argument to this function contains the text of an SQL statement
** that returns a single integer value. The statement is compiled and executed
** using database connection db. If successful, the integer value returned
** is written to *piVal and SQLITE_OK returned. Otherwise, an SQLite error
** code is returned and the value of *piVal after returning is not defined.
*/
static int getIntFromStmt(sqlite3 *db, const char *zSql, int *piVal){
  int rc = SQLITE_NOMEM;
  if( zSql ){
    sqlite3_stmt *pStmt = 0;
    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
    if( rc==SQLITE_OK ){
      if( SQLITE_ROW==sqlite3_step(pStmt) ){
        *piVal = sqlite3_column_int(pStmt, 0);
      }


      rc = sqlite3_finalize(pStmt);
    }
  }
  return rc;
}



/*
** This function is called from within the xConnect() or xCreate() method to
** determine the node-size used by the rtree table being created or connected
** to. If successful, pRtree->iNodeSize is populated and SQLITE_OK returned.
** Otherwise, an SQLite error code is returned.
**
** If this function is being called as part of an xConnect(), then the rtree
** table already exists. In this case the node-size is determined by inspecting
** the root node of the tree.
**
** Otherwise, for an xCreate(), use 64 bytes less than the database page-size. 
** This ensures that each node is stored on a single database page. If the 
** database page-size is so large that more than RTREE_MAXCELLS entries 
** would fit in a single node, use a smaller node-size.
*/
static int getNodeSize(
  sqlite3 *db,                    /* Database handle */
  Rtree *pRtree,                  /* Rtree handle */
  int isCreate                    /* True for xCreate, false for xConnect */
){
  int rc;
  char *zSql;
  if( isCreate ){
    int iPageSize;
    zSql = sqlite3_mprintf("PRAGMA %Q.page_size", pRtree->zDb);
    rc = getIntFromStmt(db, zSql, &iPageSize);
    if( rc==SQLITE_OK ){

      pRtree->iNodeSize = iPageSize-64;
      if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
        pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
      }
    }


  }else{
    zSql = sqlite3_mprintf(
        "SELECT length(data) FROM '%q'.'%q_node' WHERE nodeno = 1",
        pRtree->zDb, pRtree->zName
    );
    rc = getIntFromStmt(db, zSql, &pRtree->iNodeSize);
  }


  sqlite3_free(zSql);
  return rc;
}

/* 
** This function is the implementation of both the xConnect and xCreate
** methods of the r-tree virtual table.
**
**   argv[0]   -> module name
................................................................................

  int iErr = (argc<6) ? 2 : argc>(RTREE_MAX_DIMENSIONS*2+4) ? 3 : argc%2;
  if( aErrMsg[iErr] ){
    *pzErr = sqlite3_mprintf("%s", aErrMsg[iErr]);
    return SQLITE_ERROR;
  }






  /* Allocate the sqlite3_vtab structure */
  nDb = strlen(argv[1]);
  nName = strlen(argv[2]);
  pRtree = (Rtree *)sqlite3_malloc(sizeof(Rtree)+nDb+nName+2);
  if( !pRtree ){
    return SQLITE_NOMEM;
  }
................................................................................
  pRtree->zName = &pRtree->zDb[nDb+1];
  pRtree->nDim = (argc-4)/2;
  pRtree->nBytesPerCell = 8 + pRtree->nDim*4*2;
  pRtree->eCoordType = eCoordType;
  memcpy(pRtree->zDb, argv[1], nDb);
  memcpy(pRtree->zName, argv[2], nName);

  /* Figure out the node size to use. */
  rc = getNodeSize(db, pRtree, isCreate);










  /* Create/Connect to the underlying relational database schema. If
  ** that is successful, call sqlite3_declare_vtab() to configure
  ** the r-tree table schema.
  */
  if( rc==SQLITE_OK ){
    if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
    }else{
      char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
      char *zTmp;
      int ii;
      for(ii=4; zSql && ii<argc; ii++){
        zTmp = zSql;
        zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
        sqlite3_free(zTmp);
      }
      if( zSql ){
        zTmp = zSql;
        zSql = sqlite3_mprintf("%s);", zTmp);
        sqlite3_free(zTmp);
      }
      if( !zSql ){
        rc = SQLITE_NOMEM;
      }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
        *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
      }
      sqlite3_free(zSql);
    }
  }

  if( rc==SQLITE_OK ){
    *ppVtab = (sqlite3_vtab *)pRtree;
  }else{
    rtreeRelease(pRtree);
  }

# 2010 February 16
#
# 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.
#
#***********************************************************************
# 
# Test that nothing goes wrong if an rtree table is created, then the
# database page-size is modified. At one point (3.6.22), this was causing
# malfunctions.
#

if {![info exists testdir]} {
  set testdir [file join [file dirname $argv0] .. .. test]
} 
source $testdir/tester.tcl

ifcapable !rtree||!vacuum {
  finish_test
  return
}

do_test rtree7-1.1 {
  execsql {
    PRAGMA page_size = 1024;
    CREATE VIRTUAL TABLE rt USING rtree(id, x1, x2, y1, y2);
    INSERT INTO rt VALUES(1, 1, 2, 3, 4);
  }
} {}
do_test rtree7-1.2 {
  execsql { SELECT * FROM rt }
} {1 1.0 2.0 3.0 4.0}
do_test rtree7-1.3 {
  execsql { 
    PRAGMA page_size = 2048;
    VACUUM;
    SELECT * FROM rt;
  }
} {1 1.0 2.0 3.0 4.0}
do_test rtree7-1.4 {
  for {set i 2} {$i <= 51} {incr i} {
    execsql { INSERT INTO rt VALUES($i, 1, 2, 3, 4) }
  }
  execsql { SELECT sum(x1), sum(x2), sum(y1), sum(y2) FROM rt }
} {51.0 102.0 153.0 204.0}
do_test rtree7-1.5 {
  execsql { 
    PRAGMA page_size = 512;
    VACUUM;
    SELECT sum(x1), sum(x2), sum(y1), sum(y2) FROM rt
  }
} {51.0 102.0 153.0 204.0}

finish_test