SubsetColumnTable.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.Index;

namespace Deveel.Data.Sql.Tables {
    class SubsetColumnTable : FilterTable, IRootTable {
        private readonly int[] columnMap;
        private int[] reverseColumnMap;
        private TableInfo subsetTableInfo;
        private readonly ObjectName[] aliases;

        public SubsetColumnTable(ITable parent, int[] columnMap, ObjectName[] aliases) 
            : base(parent) {
            this.aliases = aliases;
            this.columnMap = columnMap;

            SetColumnMap(columnMap);
        }

        private void SetColumnMap(int[] mapping) {
            reverseColumnMap = new int[Parent.ColumnCount()];
            for (int i = 0; i < reverseColumnMap.Length; ++i) {
                reverseColumnMap[i] = -1;
            }

            var parentInfo = Parent.TableInfo;
            subsetTableInfo = new TableInfo(parentInfo.TableName);

            for (int i = 0; i < mapping.Length; ++i) {
                int mapTo = mapping[i];

                var origColumnInfo = Parent.TableInfo[mapTo];
                var columnInfo = new ColumnInfo(aliases[i].Name, origColumnInfo.ColumnType) {
                    DefaultExpression = origColumnInfo.DefaultExpression,
                    IsNotNull = origColumnInfo.IsNotNull,
                    IndexType = origColumnInfo.IndexType
                };

                subsetTableInfo.AddColumnSafe(columnInfo);

                reverseColumnMap[mapTo] = i;
            }

            subsetTableInfo = subsetTableInfo.AsReadOnly();
        }

        protected override int ColumnCount {
            get { return aliases.Length; }
        }

        public override TableInfo TableInfo {
            get { return subsetTableInfo; }
        }

        protected override int IndexOfColumn(ObjectName columnName) {
            for (int i = 0; i < aliases.Length; ++i) {
                if (columnName.Equals(aliases[i])) {
                    return i;
                }
            }
            return -1;
        }

        protected override ObjectName GetResolvedColumnName(int column) {
            return aliases[column];
        }

        protected override ColumnIndex GetIndex(int column, int originalColumn, ITable table) {
            // We need to map the original_column if the original column is a reference
            // in this subset column table.  Otherwise we leave as is.
            // The reason is because FilterTable pretends the call came from its
            // parent if a request is made on this table.
            int mappedOriginalColumn = originalColumn;
            if (table == this) {
                mappedOriginalColumn = columnMap[originalColumn];
            }

            return base.GetIndex(columnMap[column], mappedOriginalColumn, table);
        }

        protected override IEnumerable<int> ResolveRows(int column, IEnumerable<int> rowSet, ITable ancestor) {
            return base.ResolveRows(columnMap[column], rowSet, ancestor);
        }

        public override DataObject GetValue(long rowNumber, int columnOffset) {
            return Parent.GetValue(rowNumber, columnMap[columnOffset]);
        }

        public bool TypeEquals(IRootTable other) {
            return this == other;
        }
    }
}