anchor.diff:          let getStmtSequence (stmt:sqlite3_stmt) =
               seq {
                   while raw.SQLITE_ROW = stmt.step() do
  -                    //printfn "got_SQLITE_ROW"
  +                    printfn "got_SQLITE_ROW"
                       let doc = stmt.column_blob(0) |> BinReader.ReadDocument
                       yield doc
               }
  
positive.code:                 let ba = bson.toBinaryArray newDoc
                  if ba.Length > 16*1024*1024 then raise (MongoCode(10329, "document more than 16MB"))
                  ba
  
              let fn_insert newDoc =
                  let ba = to_bson newDoc
  
negative.code:             let (normspec,weights) = getNormalizedSpec ndx
  
              let f_min kmin = 
                  printfn "INDEX_SCAN_MIN"
                  let sql_min = sprintf "SELECT DISTINCT d.bson FROM \"%s\" d INNER JOIN \"%s\" i ON (d.did = i.doc_rowid) WHERE k >= ?" tblColl tblIndex
                  let stmt = conn.prepare(sql_min)
                  stmt.bind_blob(1, kmin)
                  stmt
  
              let f_max kmax =
                  printfn "INDEX_SCAN_MAX"
                  let sql_max = sprintf "SELECT DISTINCT d.bson FROM \"%s\" d INNER JOIN \"%s\" i ON (d.did = i.doc_rowid) WHERE k <= ?" tblColl tblIndex
                  let stmt = conn.prepare(sql_max)
                  stmt.bind_blob(1, kmax)
                  stmt
  
              let f_both (kmin,kmax) =
                  printfn "INDEX_SCAN_BOTH"
                  let sql_both = sprintf "SELECT DISTINCT d.bson FROM \"%s\" d INNER JOIN \"%s\" i ON (d.did = i.doc_rowid) WHERE k >= ? AND k <= ?" tblColl tblIndex
                  let stmt = conn.prepare(sql_both)
                  stmt.bind_blob(1, kmin)
  