public virtual VfpExpression Visit(VfpLimitExpression expression)
{
return(new VfpLimitExpression(expression.ResultType,
expression.Argument.Accept(this),
expression.Limit.Accept(this),
expression.WithTies));
}
private static VfpLimitExpression GetVfpLimitExpression(VfpLimitExpression limitExpression, VfpProjectExpression projectExpression)
{
var keyMembers = GetKeyMembers(projectExpression);
if (!keyMembers.Any())
{
return(null);
}
var sortBinding = GetSortBinding(keyMembers, projectExpression.Input, projectExpression);
var newProject = sortBinding.Project(projectExpression.Projection);
return(new VfpLimitExpression(limitExpression.ResultType,
newProject,
limitExpression.Limit,
limitExpression.WithTies));
}
private static VfpLimitExpression GetVfpLimitExpression(VfpLimitExpression limitExpression, VfpFilterExpression filterExpression)
{
var keyMembers = GetKeyMembers(filterExpression);
if (!keyMembers.Any())
{
return(null);
}
var sortBinding = GetSortBinding(keyMembers, filterExpression.Input, filterExpression);
var newFilter = sortBinding.Filter(filterExpression.Predicate);
return(new VfpLimitExpression(limitExpression.ResultType,
newFilter,
limitExpression.Limit,
limitExpression.WithTies));
}
public override VfpExpression Visit(VfpLimitExpression expression)
{
var sortExpression = expression.Argument as VfpSortExpression;
if (sortExpression == null)
{
var newLimitExpression = GetVfpLimitExpression(expression, expression.Argument as VfpProjectExpression) ??
GetVfpLimitExpression(expression, expression.Argument as VfpFilterExpression) ??
GetVfpLimitExpression(expression, expression.Argument as VfpScanExpression);
if (newLimitExpression != null)
{
return(base.Visit(newLimitExpression));
}
}
return(base.Visit(expression));
}
private VfpLimitExpression GetVfpLimitExpression(VfpLimitExpression limitExpression, VfpScanExpression scanExpression)
{
if (scanExpression == null)
{
return(null);
}
var keyMembers = GetKeyMembers(scanExpression.Target.ElementType.KeyMembers);
if (!keyMembers.Any())
{
return(null);
}
var variableReference = new VfpVariableReferenceExpression(scanExpression.ResultType, GetUniqueVariableName());
var expressionBinding = new VfpExpressionBinding(scanExpression, variableReference);
var sortClauses = GetSortClauses(keyMembers, expressionBinding).ToList().AsReadOnly();
var sortExpression = new VfpSortExpression(scanExpression.ResultType, expressionBinding, sortClauses);
return(new VfpLimitExpression(limitExpression.ResultType,
sortExpression,
limitExpression.Limit,
limitExpression.WithTies));
}
