QueryExtensions.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 System.Linq;

using Deveel.Data.Security;
using Deveel.Data.Sql.Query;
using Deveel.Data.Transactions;

namespace Deveel.Data.Sql.Views {
    public static class QueryExtensions {
        public static bool ViewExists(this IQuery context, ObjectName viewName) {
            return context.ObjectExists(DbObjectType.View, viewName);
        }

        public static void DefineView(this IQuery context, ViewInfo viewInfo, bool replaceIfExists) {
            var tablesInPlan = viewInfo.QueryPlan.DiscoverTableNames();
            foreach (var tableName in tablesInPlan) {
                if (!context.UserCanSelectFromTable(tableName))
                    throw new InvalidAccessException(context.UserName(), tableName);
            }

            if (context.ViewExists(viewInfo.ViewName)) {
                if (!replaceIfExists)
                    throw new InvalidOperationException(
                        String.Format("The view {0} already exists and the REPLCE clause was not specified.", viewInfo.ViewName));

                context.DropObject(DbObjectType.View, viewInfo.ViewName);
            }

            context.CreateObject(viewInfo);

            // The initial grants for a view is to give the user who created it
            // full access.
            using (var systemContext = context.Direct()) {
                systemContext.GrantToUserOnTable(viewInfo.ViewName, context.UserName(), Privileges.TableAll);
            }
        }

        public static void DefineView(this IQuery context, ObjectName viewName, IQueryPlanNode queryPlan, bool replaceIfExists) {
            // We have to execute the plan to get the TableInfo that represents the
            // result of the view execution.
            var table = queryPlan.Evaluate(context);
            var tableInfo = table.TableInfo.Alias(viewName);

            var viewInfo = new ViewInfo(tableInfo, null, queryPlan);
            context.DefineView(viewInfo, replaceIfExists);
        }

        public static void DropView(this IQuery context, ObjectName viewName) {
            DropView(context, viewName, false);
        }

        public static void DropView(this IQuery context, ObjectName viewName, bool ifExists) {
            context.DropViews(new[] { viewName }, ifExists);
        }

        public static void DropViews(this IQuery context, IEnumerable<ObjectName> viewNames) {
            DropViews(context, viewNames, false);
        }

        public static void DropViews(this IQuery context, IEnumerable<ObjectName> viewNames, bool onlyIfExists) {
            var viewNameList = viewNames.ToList();
            foreach (var tableName in viewNameList) {
                if (!context.UserCanDropObject(DbObjectType.View, tableName))
                    throw new MissingPrivilegesException(context.UserName(), tableName, Privileges.Drop);
            }

            // If the 'only if exists' flag is false, we need to check tables to drop
            // exist first.
            if (!onlyIfExists) {
                // For each table to drop.
                foreach (var viewName in viewNameList) {
                    // If view doesn't exist, throw an error
                    if (!context.ViewExists(viewName)) {
                        throw new ObjectNotFoundException(viewName, String.Format("The view '{0}' does not exist and cannot be dropped.", viewName));
                    }
                }
            }

            foreach (var viewName in viewNameList) {
                // Does the table already exist?
                if (context.ViewExists(viewName)) {
                    // Drop table in the transaction
                    context.DropObject(DbObjectType.Table, viewName);

                    // Revoke all the grants on the table
                    context.RevokeAllGrantsOnView(viewName);
                }
            }
        }

        public static View GetView(this IQuery context, ObjectName viewName) {
            return context.GetObject(DbObjectType.View, viewName, AccessType.Read) as View;
        }

        public static IQueryPlanNode GetViewQueryPlan(this IQuery context, ObjectName viewName) {
            var view = context.GetView(viewName);
            return view == null ? null : view.QueryPlan;
        }
    }
}