SqlExpressionExtensions.cs

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// 
//  Copyright 2010-2015 Deveel
// 
//    Licensed under the Apache License, Version 2.0 (the "License");
//    you may not use this file except in compliance with the License.
//    You may obtain a copy of the License at
// 
//        http://www.apache.org/licenses/LICENSE-2.0
// 
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS,
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//    See the License for the specific language governing permissions and
//    limitations under the License.
//

using System;

using Deveel.Data;
using Deveel.Data.Sql.Objects;
using Deveel.Data.Sql.Query;
using Deveel.Data.Types;

namespace Deveel.Data.Sql.Expressions {
    public static class SqlExpressionExtensions {
        public static ObjectName AsReferenceName(this SqlExpression expression) {
            var refExpression = expression as SqlReferenceExpression;
            if (refExpression == null)
                return null;

            return refExpression.ReferenceName;
        }

        public static IQueryPlanNode AsQueryPlan(this SqlExpression expression) {
            var constantExp = expression as SqlConstantExpression;
            if (constantExp == null)
                return null;

            var value = constantExp.Value;
            if (value.Value is SqlQueryObject)
                return ((SqlQueryObject) value.Value).QueryPlan;

            return null;
        }

        public static DataObject EvaluateToConstant(this SqlExpression expression, EvaluateContext context) {
            var evalExp = expression.Evaluate(context);
            if (evalExp == null)
                throw new InvalidOperationException();

            var constantExp = evalExp as SqlConstantExpression;
            if (constantExp == null)
                throw new InvalidOperationException();

            return constantExp.Value;
        }

        public static DataObject EvaluateToConstant(this SqlExpression expression, IRequest request, IVariableResolver variableResolver) {
            return expression.EvaluateToConstant(new EvaluateContext(request, variableResolver));
        }

        public static SqlType ReturnType(this SqlExpression expression, IRequest query, IVariableResolver variableResolver) {
            var visitor = new ReturnTypeVisitor(query, variableResolver);
            return visitor.GetType(expression);
        }

        public static bool HasAggregate(this SqlExpression expression, IRequest query) {
            var visitor = new AggregateChecker(query);
            return visitor.HasAggregate(expression);
        }

        public static bool IsConstant(this SqlExpression expression) {
            var visitor = new ConstantVisitor();
            visitor.Visit(expression);
            return visitor.IsConstant;
        }
    }
}