QueryExpressionExtensions.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 System.Collections.Generic;

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

namespace Deveel.Data.Sql.Query {
    static class QueryExpressionExtensions {
        public static void DiscoverTableNames(this SqlExpression expression, IList<ObjectName> tableNames) {
            var visitor = new TableNamesVisitor();
            visitor.Visit(expression);
        }

        public static IList<QueryReference> DiscoverQueryReferences(this SqlExpression expression, ref int level) {
            return DiscoverQueryReferences(expression, ref level, new List<QueryReference>());
        }

        public static IList<QueryReference> DiscoverQueryReferences(this SqlExpression expression, ref int level, IList<QueryReference> list) {
            var visitor = new QueryReferencesVisitor(list, level);
            visitor.Visit(expression);
            level = visitor.Level;
            return visitor.References;
        }

        public static IEnumerable<ObjectName> DiscoverReferences(this SqlExpression expression) {
            var discovery = new ReferenceDiscovery();
            return discovery.Discover(expression);
        }

        public static bool HasSubQuery(this SqlExpression expression) {
            return new SubQueryDiscovery().Verify(expression);
        }

        #region ColumnNameDiscovery

        class ReferenceDiscovery : SqlExpressionVisitor {
            private readonly List<ObjectName> columnNames;

            public ReferenceDiscovery() {
                columnNames = new List<ObjectName>();
            }

            public IEnumerable<ObjectName> Discover(SqlExpression expression) {
                Visit(expression);
                return columnNames.ToArray();
            }

            public override SqlExpression VisitConstant(SqlConstantExpression constant) {
                var value = constant.Value;
                if (value.Type is ArrayType) {
                    var array = (SqlArray) value.Value;
                    foreach (var element in array) {
                        columnNames.AddRange(element.DiscoverReferences());
                    }
                }

                return base.VisitConstant(constant);
            }

            public override SqlExpression VisitFunctionCall(SqlFunctionCallExpression expression) {
                var args = expression.Arguments;
                foreach (var arg in args) {
                    columnNames.AddRange(arg.DiscoverReferences());
                }

                return base.VisitFunctionCall(expression);
            }

            public override SqlExpression VisitReference(SqlReferenceExpression reference) {
                columnNames.Add(reference.ReferenceName);
                return base.VisitReference(reference);
            }
        }

        #endregion

        #region SubQueryDiscovery

        private class SubQueryDiscovery : SqlExpressionVisitor {
            private bool hasSubQuery;

            public bool Verify(SqlExpression expression) {
                Visit(expression);
                return hasSubQuery;
            }

            public override SqlExpression VisitConstant(SqlConstantExpression constant) {
                if (constant.Value.Type is QueryType)
                    hasSubQuery = true;

                return base.VisitConstant(constant);
            }
        }

        #endregion
    }
}