SQLite

  /* Create/Connect to the underlying relational database schema. If
  ** that is successful, call sqlite3_declare_vtab() to configure
  ** the r-tree table schema.
  */
  pSql = sqlite3_str_new(db);
  sqlite3_str_appendf(pSql, "CREATE TABLE x(_shape");
  pRtree->nAux = 1;         /* Add one for _shape */
  pRtree->nAuxNotNull = 1;  /* The _shape column is always not-null */
  for(ii=3; ii<argc; ii++){
    pRtree->nAux++;
    sqlite3_str_appendf(pSql, ",%s", argv[ii]);
  }
  sqlite3_str_appendf(pSql, ");");
  zSql = sqlite3_str_finish(pSql);
  if( !zSql ){

  RtreeCursor *pCsr = (RtreeCursor *)cur;
  RtreeSearchPoint *p = rtreeSearchPointFirst(pCsr);
  int rc = SQLITE_OK;
  RtreeNode *pNode = rtreeNodeOfFirstSearchPoint(pCsr, &rc);

  if( rc ) return rc;
  if( p==0 ) return SQLITE_OK;
  if( i==0 && sqlite3_vtab_nochange(ctx) ) return SQLITE_OK;
  if( i<=pRtree->nAux ){
    if( !pCsr->bAuxValid ){
      if( pCsr->pReadAux==0 ){
        rc = sqlite3_prepare_v3(pRtree->db, pRtree->zReadAuxSql, -1, 0,
                                &pCsr->pReadAux, 0);
        if( rc ) return rc;
      }

    ** since the write might do a rebalance which would disrupt the read
    ** cursor. */
    return SQLITE_LOCKED_VTAB;
  }
  rtreeReference(pRtree);
  assert(nData>=1);


  oldRowidValid = sqlite3_value_type(aData[0])!=SQLITE_NULL;;
  oldRowid = oldRowidValid ? sqlite3_value_int64(aData[0]) : 0;
  newRowidValid = nData>1 && sqlite3_value_type(aData[1])!=SQLITE_NULL;
  newRowid = newRowidValid ? sqlite3_value_int64(aData[1]) : 0;
  cell.iRowid = newRowid;

  if( nData>1                                 /* not a DELETE */

      }
      goto geopoly_update_end;
    }
    coordChange = 1;

    /* If a rowid value was supplied, check if it is already present in 
    ** the table. If so, the constraint has failed. */
    if( newRowidValid && (!oldRowidValid || oldRowid!=newRowid) ){
      int steprc;
      sqlite3_bind_int64(pRtree->pReadRowid, 1, cell.iRowid);
      steprc = sqlite3_step(pRtree->pReadRowid);
      rc = sqlite3_reset(pRtree->pReadRowid);
      if( SQLITE_ROW==steprc ){
        if( sqlite3_vtab_on_conflict(pRtree->db)==SQLITE_REPLACE ){
          rc = rtreeDeleteRowid(pRtree, cell.iRowid);

  /* Change the data */
  if( rc==SQLITE_OK ){
    sqlite3_stmt *pUp = pRtree->pWriteAux;
    int jj;
    int nChange = 0;
    sqlite3_bind_int64(pUp, 1, cell.iRowid);
    assert( pRtree->nAux>=1 );
    if( sqlite3_value_nochange(aData[2]) ){
      sqlite3_bind_null(pUp, 2);
    }else{
      sqlite3_bind_value(pUp, 2, aData[2]);
      nChange = 1;
    }
    for(jj=1; jj<pRtree->nAux; jj++){
      nChange++;
      sqlite3_bind_value(pUp, jj+2, aData[jj+2]);
    }
    if( nChange ){
      sqlite3_step(pUp);
      rc = sqlite3_reset(pUp);
    }
  }

  int iNodeSize;              /* Size in bytes of each node in the node table */
  u8 nDim;                    /* Number of dimensions */
  u8 nDim2;                   /* Twice the number of dimensions */
  u8 eCoordType;              /* RTREE_COORD_REAL32 or RTREE_COORD_INT32 */
  u8 nBytesPerCell;           /* Bytes consumed per cell */
  u8 inWrTrans;               /* True if inside write transaction */
  u8 nAux;                    /* # of auxiliary columns in %_rowid */
  u8 nAuxNotNull;             /* Number of initial not-null aux columns */
  int iDepth;                 /* Current depth of the r-tree structure */
  char *zDb;                  /* Name of database containing r-tree table */
  char *zName;                /* Name of r-tree table */ 
  u32 nBusy;                  /* Current number of users of this structure */
  i64 nRowEst;                /* Estimated number of rows in this table */
  u32 nCursor;                /* Number of open cursors */
  u32 nNodeRef;               /* Number RtreeNodes with positive nRef */

    }else{
      sqlite3_str *p = sqlite3_str_new(db);
      int ii;
      char *zSql;
      sqlite3_str_appendf(p, "UPDATE \"%w\".\"%w_rowid\"SET ", zDb, zPrefix);
      for(ii=0; ii<pRtree->nAux; ii++){
        if( ii ) sqlite3_str_append(p, ",", 1);
        if( ii<pRtree->nAuxNotNull ){
          sqlite3_str_appendf(p,"a%d=coalesce(?%d,a%d)",ii,ii+2,ii);
        }else{
          sqlite3_str_appendf(p,"a%d=?%d",ii,ii+2);
        }
      }
      sqlite3_str_appendf(p, " WHERE rowid=?1");
      zSql = sqlite3_str_finish(p);
      if( zSql==0 ){
        rc = SQLITE_NOMEM;
      }else{
        rc = sqlite3_prepare_v3(db, zSql, -1, SQLITE_PREPARE_PERSISTENT,

  FROM geo1, querypoly
 WHERE NOT geopoly_within(_shape, poly);
SELECT geopoly_svg(poly, 
         printf('style="fill:%s;fill-opacity:0.5;"',clr)
       )
  FROM querypoly;
.print '</svg>'

.print '<h1>Color-Change For Overlapping Elements</h1>'
BEGIN;
UPDATE geo1
   SET clr=CASE WHEN rowid IN (SELECT geo1.rowid FROM geo1, querypoly
                                WHERE geopoly_overlap(_shape,poly))
           THEN 'red' ELSE 'blue' END;
.print '<svg width="1000" height="800" style="border:1px solid black">'
SELECT geopoly_svg(_shape,
         printf('style="fill:none;stroke:%s;stroke-width:1"',geo1.clr)
       )
  FROM geo1;
SELECT geopoly_svg(poly,'style="fill:none;stroke:black;stroke-width:2"')
  FROM querypoly;
ROLLBACK;
.print '</svg>'

.print '<h1>Color-Change And Move Overlapping Elements</h1>'
BEGIN;
UPDATE geo1
   SET clr=CASE WHEN rowid IN (SELECT geo1.rowid FROM geo1, querypoly
                                WHERE geopoly_overlap(_shape,poly))
           THEN 'red' ELSE 'blue' END;
UPDATE geo1
   SET _shape=geopoly_xform(_shape,1,0,0,1,300,0)
 WHERE geopoly_overlap(_shape,(SELECT poly FROM querypoly));
.print '<svg width="1000" height="800" style="border:1px solid black">'
SELECT geopoly_svg(_shape,
         printf('style="fill:none;stroke:%s;stroke-width:1"',geo1.clr)
       )
  FROM geo1;
SELECT geopoly_svg(poly,'style="fill:none;stroke:black;stroke-width:2"')
  FROM querypoly;
ROLLBACK;
.print '</svg>'

.print '</html>'