/// <summary>
/// Implement the skipping. We have a main limitation: we currently know only how to implement integer skipping.
/// We implement with "if" statements to support composability, even if it means running longer in the end...
/// We actually return nothing when goes - we aren't really a final result the way "Count" is.
/// </summary>
/// <param name="resultOperator"></param>
/// <param name="queryModel"></param>
/// <param name="_codeEnv"></param>
/// <returns></returns>
public void ProcessResultOperator(ResultOperatorBase resultOperator, QueryModel queryModel, IGeneratedQueryCode codeEnv, ICodeContext codeContext, CompositionContainer container)
{
///
/// Quick checks to make sure
///
if (codeEnv == null)
throw new ArgumentNullException("codeEnv cannot be null");
var take = resultOperator as TakeResultOperator;
var skip = resultOperator as SkipResultOperator;
if (take == null && skip == null)
{
throw new ArgumentNullException("resultOperator must not be null and must represent either a take or a skip operation!");
}
if (take != null && take.Count.Type != typeof(int))
throw new ArgumentException("Take operator count must be an integer!");
if (skip != null && skip.Count.Type != typeof(int))
throw new ArgumentException("Skip operator count must be an integer!");
// If this is a "global" take, then we need to declare the variable a bit specially.
// Global: we have a limit on the number of objects that goes across events. We test this by seeing if this
// is a sub-query that is registered (or not).
var isGlobalTake = codeContext.IsInTopLevelQueryModel(queryModel);
// Now, we create a count variable and that is how we will tell if we are still skipping or
// taking. It must be declared in the current block, before our current code! :-)
var counter = DeclarableParameter.CreateDeclarableParameterExpression(typeof(int), otherDependencies: codeContext.LoopIndexVariable.Return<IDeclaredParameter>());
if (isGlobalTake)
{
counter.DeclareAsStatic = true;
codeEnv.Add(counter);
} else
{
codeEnv.AddOutsideLoop(counter);
}
var comparison = StatementIfOnCount.ComparisonOperator.LessThanEqual;
IValue limit = null;
if (skip != null)
{
comparison = StatementIfOnCount.ComparisonOperator.GreaterThan;
limit = ExpressionToCPP.GetExpression(skip.Count, codeEnv, codeContext, container);
}
else
{
limit = ExpressionToCPP.GetExpression(take.Count, codeEnv, codeContext, container);
}
codeEnv.Add(new StatementIfOnCount(counter, limit, comparison));
///
/// We are particularly fortunate here. We don't have to update the Loop variable - whatever it is, is
/// still the right one! Normally we'd have to futz with the LoopVariable in code context because we
/// were iterating over something new. :-) Easy!
///
}
/// <summary>
/// Implement the skipping. We have a main limitation: we currently know only how to implement integer skipping.
/// We implement with "if" statements to support composability, even if it means running longer in the end...
/// We actually return nothing when goes - we aren't really a final result the way "Count" is.
/// </summary>
/// <param name="resultOperator"></param>
/// <param name="queryModel"></param>
/// <param name="_codeEnv"></param>
/// <returns></returns>
public void ProcessResultOperator(ResultOperatorBase resultOperator, QueryModel queryModel, IGeneratedQueryCode codeEnv, ICodeContext codeContext, CompositionContainer container)
{
///
/// Quick checks to make sure
///
if (codeEnv == null)
{
throw new ArgumentNullException("codeEnv cannot be null");
}
var take = resultOperator as TakeResultOperator;
var skip = resultOperator as SkipResultOperator;
if (take == null && skip == null)
{
throw new ArgumentNullException("resultOperator must not be null and must represent either a take or a skip operation!");
}
if (take != null && take.Count.Type != typeof(int))
{
throw new ArgumentException("Take operator count must be an integer!");
}
if (skip != null && skip.Count.Type != typeof(int))
{
throw new ArgumentException("Skip operator count must be an integer!");
}
// If this is a "global" take, then we need to declare the variable a bit specially.
// Global: we have a limit on the number of objects that goes across events. We test this by seeing if this
// is a sub-query that is registered (or not).
var isGlobalTake = codeContext.IsInTopLevelQueryModel(queryModel);
// Now, we create a count variable and that is how we will tell if we are still skipping or
// taking. It must be declared in the current block, before our current code! :-)
var counter = DeclarableParameter.CreateDeclarableParameterExpression(typeof(int), otherDependencies: codeContext.LoopIndexVariable.Return <IDeclaredParameter>());
if (isGlobalTake)
{
counter.DeclareAsStatic = true;
codeEnv.Add(counter);
}
else
{
codeEnv.AddOutsideLoop(counter);
}
var comparison = StatementIfOnCount.ComparisonOperator.LessThanEqual;
IValue limit = null;
if (skip != null)
{
comparison = StatementIfOnCount.ComparisonOperator.GreaterThan;
limit = ExpressionToCPP.GetExpression(skip.Count, codeEnv, codeContext, container);
}
else
{
limit = ExpressionToCPP.GetExpression(take.Count, codeEnv, codeContext, container);
}
codeEnv.Add(new StatementIfOnCount(counter, limit, comparison));
///
/// We are particularly fortunate here. We don't have to update the Loop variable - whatever it is, is
/// still the right one! Normally we'd have to futz with the LoopVariable in code context because we
/// were iterating over something new. :-) Easy!
///
}