public SqlExpression Prepare(SqlExpression expression)
{
var queryExpression = (SqlQueryExpression) expression;
var queryFrom = QueryExpressionFrom.Create(context, queryExpression);
queryFrom.Parent = parent;
var plan = planner.PlanQuery(context, queryExpression, queryFrom, null, null);
return SqlExpression.Constant(new Field(new QueryType(), new SqlQueryObject(new CachePointNode(plan))));
}