/// <summary>
/// Visits a <see cref="WhereOperator" /> and coalesces it with any possible child operators.
/// </summary>
/// <param name="op">The operator to visit.</param>
/// <returns>The coalesced operator.</returns>
protected internal override QueryOperator VisitWhere(WhereOperator op)
{
var source = VisitAndConvert <MonadMember>(op.Source);
var predicate = Visit(op.Predicate);
var srcOperator = source.QueryNodeType == QueryNodeType.Operator ? (QueryOperator)source : null;
var srcWhere = srcOperator != null && srcOperator.NodeType == OperatorType.Where ? (WhereOperator)srcOperator : null;
if (srcWhere != null && op.ElementType == srcWhere.ElementType)
{
var p = Expression.Parameter(op.ElementType);
if (TryExtractNullaryLambdaBody(srcWhere.Predicate, out Expression predicate1) && TryExtractNullaryLambdaBody(predicate, out Expression predicate2))
{
var reduced1 = BetaReducer.Reduce(Expression.Invoke(predicate1, p));
var reduced2 = BetaReducer.Reduce(Expression.Invoke(predicate2, p));
return(op.QueryExpressionFactory.Where(
op.ElementType,
srcWhere.Source,
DefaultQueryExpressionFactory.Instance.LambdaAbstraction(
Expression.Lambda(
Expression.Lambda(
Expression.AndAlso(reduced1, reduced2),
p
)
),
Array.Empty <QueryTree>()
)
));
}
var predicateType = typeof(Func <,>).MakeGenericType(p.Type, typeof(bool));
var p1 = Expression.Parameter(predicateType);
var p2 = Expression.Parameter(predicateType);
return(op.QueryExpressionFactory.Where(
op.ElementType,
srcWhere.Source,
DefaultQueryExpressionFactory.Instance.LambdaAbstraction(
Expression.Lambda(
Expression.Lambda(
Expression.AndAlso(
Expression.Invoke(p1, p),
Expression.Invoke(p2, p)
),
p
),
p1,
p2
),
new[] { srcWhere.Predicate, predicate }
)
));
}
return(op.Update(source, predicate));
}
/// <summary>
/// Visits a <see cref="WhereOperator" /> node.
/// </summary>
/// <param name="op">Node to visit.</param>
/// <returns>Result of visiting the node.</returns>
protected internal override QueryOperator VisitWhere(WhereOperator op)
{
var src = VisitAndConvert <MonadMember>(op.Source);
var pred = Visit(op.Predicate);
if (src != op.Source || pred != op.Predicate)
{
return(MakeWhere(op, src, pred));
}
return(op);
}
/// <summary>
/// Makes a <see cref="WhereOperator" /> with the given children.
/// </summary>
/// <param name="node">Original query expression.</param>
/// <param name="source">Source query expression.</param>
/// <param name="predicate">Predicate query expression.</param>
/// <returns>Representation of the original query expression.</returns>
protected sealed override QueryOperator MakeWhere(WhereOperator node, MonadMember source, QueryTree predicate)
{
return(node.QueryExpressionFactory.Where(node.ElementType, source, predicate));
}
/// <summary>
/// Creates a textual representation of the WhereOperator with the given children.
/// </summary>
/// <param name="node">Original query expression.</param>
/// <param name="source">Source query expression.</param>
/// <param name="predicate">Predicate query expression.</param>
/// <returns>Representation of the original query expression.</returns>
protected override string MakeWhere(WhereOperator node, string source, string predicate)
{
return(string.Format(CultureInfo.InvariantCulture, "@Where({0}, {1})", source, predicate));
}
/// <summary>
/// Makes a <see cref="WhereOperator" /> with the given children.
/// </summary>
/// <param name="node">Original query expression.</param>
/// <param name="source">Source query expression.</param>
/// <param name="elementType">Element type for the resulting operator.</param>
/// <param name="predicate">Predicate query expression.</param>
/// <returns>Representation of the original query expression.</returns>
protected virtual QueryOperator MakeWhere(WhereOperator node, Type elementType, MonadMember source, QueryTree predicate)
{
return(node.QueryExpressionFactory.Where(elementType, source, predicate));
}