private DryadQueryNode VisitDistinct(QueryNodeInfo source,
Expression comparerExpr,
Expression queryExpr)
{
DryadQueryNode child = this.Visit(source);
Type keyType = child.OutputTypes[0];
if (comparerExpr == null && !TypeSystem.HasDefaultEqualityComparer(keyType))
{
throw DryadLinqException.Create(HpcLinqErrorCode.ComparerMustBeSpecifiedOrKeyTypeMustBeIEquatable,
string.Format(SR.ComparerMustBeSpecifiedOrKeyTypeMustBeIEquatable, keyType),
queryExpr);
}
object comparer = null;
if (comparerExpr != null)
{
ExpressionSimplifier<object> evaluator = new ExpressionSimplifier<object>();
comparer = evaluator.Eval(comparerExpr);
}
LambdaExpression keySelectExpr = IdentityFunction.Instance(keyType);
if (!child.OutputPartition.IsPartitionedBy(keySelectExpr, comparer))
{
if (child.IsDynamic || child.OutputPartition.Count > 1)
{
child = new DryadDistinctNode(true, comparerExpr, queryExpr, child);
bool isDynamic = (StaticConfig.DynamicOptLevel & StaticConfig.DynamicHashPartitionLevel) != 0;
child = new DryadHashPartitionNode(keySelectExpr,
comparerExpr,
child.OutputPartition.Count,
isDynamic,
queryExpr,
child);
child = new DryadMergeNode(false, false, queryExpr, child);
}
}
DryadQueryNode resNode = new DryadDistinctNode(false, comparerExpr, queryExpr, child);
return resNode;
}
internal virtual string Visit(DryadDistinctNode node,
CodeMemberMethod vertexMethod,
string[] readerNames,
string[] writerNames)
{
return node.AddVertexCode(vertexMethod, readerNames, writerNames);
}