RangeSelectNode.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.Index;
using Deveel.Data.Serialization;
using Deveel.Data.Sql.Expressions;
using Deveel.Data.Sql.Tables;

namespace Deveel.Data.Sql.Query {
    [Serializable]
    class RangeSelectNode : SingleQueryPlanNode {
        public RangeSelectNode(IQueryPlanNode child, SqlExpression expression)
            : base(child) {
            Expression = expression;
        }

        private RangeSelectNode(ObjectData data)
            : base(data) {
            Expression = data.GetValue<SqlExpression>("Expression");
        }

        public SqlExpression Expression { get; private set; }

        protected override void GetData(SerializeData data) {
            data.SetValue("Expression", Expression);
        }

        public override ITable Evaluate(IRequest context) {
            var t = Child.Evaluate(context);

            var exp = Expression;

            // Assert that all variables in the expression are identical.
            var columnNames = exp.DiscoverReferences();
            ObjectName columnName = null;
            foreach (var cv in columnNames) {
                if (columnName != null && !cv.Equals(columnName))
                    throw new InvalidOperationException("Range plan does not contain common column.");

                columnName = cv;
            }

            // Find the variable field in the table.
            var col = t.IndexOfColumn(columnName);
            if (col == -1)
                throw new InvalidOperationException("Could not find column reference in table: " + columnName);

            var field = t.TableInfo[col];

            // Calculate the range
            var range = new IndexRangeSet();
            var calculator = new RangeSetCalculator(context, field, range);
            range = calculator.Calculate(exp);

            // Select the range from the table
            var ranges = range.ToArray();
            return t.SelectRange(columnName, ranges);
        }

        #region RangeSetUpdater

        class RangeSetUpdater : SqlExpressionVisitor {
            private IndexRangeSet indexRangeSet;
            private readonly IRequest context;
            private readonly ColumnInfo field;

            public RangeSetUpdater(IRequest context, ColumnInfo field, IndexRangeSet indexRangeSet) {
                this.context = context;
                this.field = field;
                this.indexRangeSet = indexRangeSet;
            }

            public IndexRangeSet Update(SqlExpression expression) {
                Visit(expression);
                return indexRangeSet;
            }

            public override SqlExpression VisitBinary(SqlBinaryExpression binaryEpression) {
                var op = binaryEpression.ExpressionType;

                // Evaluate to an object
                var value = binaryEpression.Right.EvaluateToConstant(context, null);

                // If the evaluated object is not of a comparable type, then it becomes
                // null.
                var fieldType = field.ColumnType;
                if (!value.Type.IsComparable(fieldType))
                    value = DataObject.Null(fieldType);

                // Intersect this in the range set
                indexRangeSet = indexRangeSet.Intersect(op, value);

                return base.VisitBinary(binaryEpression);
            }
        }

        #endregion

        #region RangeSetCalculator

        class RangeSetCalculator : SqlExpressionVisitor {
            private IndexRangeSet rangeSet;
            private readonly IRequest context;
            private readonly ColumnInfo field;

            public RangeSetCalculator(IRequest context, ColumnInfo field, IndexRangeSet rangeSet) {
                this.context = context;
                this.field = field;
                this.rangeSet = rangeSet;
            }

            private IndexRangeSet UpdateRange(SqlExpression expression) {
                var updater = new RangeSetUpdater(context, field, rangeSet);
                return updater.Update(expression);
            }

            private IndexRangeSet CalcExpression(SqlExpression expression) {
                var indexRangeSet = new IndexRangeSet();
                var calculator = new RangeSetCalculator(context, field, indexRangeSet);
                return calculator.Calculate(expression);
            }

            public override SqlExpression VisitBinary(SqlBinaryExpression binaryEpression) {
                if (binaryEpression.ExpressionType == SqlExpressionType.And) {
                    rangeSet = UpdateRange(binaryEpression.Left);
                    rangeSet = UpdateRange(binaryEpression.Right);
                } else if (binaryEpression.ExpressionType == SqlExpressionType.Or) {
                    var left = CalcExpression(binaryEpression.Left);
                    var right = CalcExpression(binaryEpression.Right);

                    rangeSet = rangeSet.Union(left);
                    rangeSet = rangeSet.Union(right);
                } else {
                    rangeSet = UpdateRange(binaryEpression);
                }

                return base.VisitBinary(binaryEpression);
            }

            public IndexRangeSet Calculate(SqlExpression expression) {
                Visit(expression);
                return rangeSet;
            }
        }

        #endregion
    }
}