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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <functional>
#include <map>
#include <memory>
#include <string>
#include <tuple>
#include <vector>
#include "mongo/base/status.h"
#include "mongo/base/status_with.h"
#include "mongo/base/string_data.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/views/durable_view_catalog.h"
#include "mongo/db/views/resolved_view.h"
#include "mongo/db/views/view.h"
#include "mongo/db/views/view_graph.h"
#include "mongo/platform/mutex.h"
#include "mongo/util/concurrency/with_lock.h"
#include "mongo/util/string_map.h"
namespace mongo {
class OperationContext;
class Database;
/**
* In-memory data structure for view definitions. Instances returned by get() are immutable,
* modifications through the static functions copy the existing instance and perform the
* modification on the copy. A new call to get() is necessary to observe the modification.
*
* Writes via the static functions are thread-safe and serialized with a mutex per Database -- this
* is needed as concurrent updates may happen through direct writes to the views catalog collection.
*
* The static methods refresh the in-memory map with the views catalog collection if necessary,
* throwing if the refresh fails.
*/
class ViewCatalog {
public:
using ViewMap = StringMap<std::shared_ptr<ViewDefinition>>;
using ViewIteratorCallback = std::function<bool(const ViewDefinition& view)>;
static std::shared_ptr<const ViewCatalog> get(const Database* db);
static void set(Database* db, std::unique_ptr<ViewCatalog> catalog);
explicit ViewCatalog(std::unique_ptr<DurableViewCatalog> durable)
: _durable(std::move(durable)), _valid(false), _viewGraphNeedsRefresh(true) {}
/**
* Iterates through the catalog, applying 'callback' to each view. This callback function
* executes under the catalog's mutex, so it must not access other methods of the catalog,
* acquire locks or run for a long time. If the 'callback' returns false, the iterator exists
* early.
*/
void iterate(ViewIteratorCallback callback) const;
/**
* Create a new view 'viewName' with contents defined by running the specified aggregation
* 'pipeline' with collation 'collation' on a collection or view 'viewOn'. This method will
* check correctness with respect to the view catalog, but will not check for conflicts with the
* database's catalog, so the check for an existing collection with the same name must be done
* before calling createView.
*
* Must be in WriteUnitOfWork. View creation rolls back if the unit of work aborts.
*/
static Status createView(OperationContext* opCtx,
const Database* db,
const NamespaceString& viewName,
const NamespaceString& viewOn,
const BSONArray& pipeline,
const BSONObj& collation);
/**
* Drop the view named 'viewName'.
*
* Must be in WriteUnitOfWork. The drop rolls back if the unit of work aborts.
*/
static Status dropView(OperationContext* opCtx,
const Database* db,
const NamespaceString& viewName);
/**
* Modify the view named 'viewName' to have the new 'viewOn' and 'pipeline'.
*
* Must be in WriteUnitOfWork. The modification rolls back if the unit of work aborts.
*/
static Status modifyView(OperationContext* opCtx,
const Database* db,
const NamespaceString& viewName,
const NamespaceString& viewOn,
const BSONArray& pipeline);
/**
* Look up the 'nss' in the view catalog, returning a shared pointer to a View definition, or
* nullptr if it doesn't exist.
*/
std::shared_ptr<const ViewDefinition> lookup(OperationContext* opCtx, StringData nss) const;
/**
* Same functionality as above, except this function skips validating durable views in the view
* catalog.
*/
std::shared_ptr<const ViewDefinition> lookupWithoutValidatingDurableViews(
OperationContext* opCtx, StringData nss) const;
/**
* Resolve the views on 'nss', transforming the pipeline appropriately. This function returns a
* fully-resolved view definition containing the backing namespace, the resolved pipeline and
* the collation to use for the operation.
*/
StatusWith<ResolvedView> resolveView(OperationContext* opCtx, const NamespaceString& nss) const;
/**
* Usage statistics about this view catalog.
* Total views = internal + userViews + userTimeseries.
*/
struct Stats {
int userViews = 0;
int userTimeseries = 0;
int internal = 0;
};
/**
* Returns statistics for this view catalog.
*/
Stats getStats() const;
/**
* Returns Status::OK with the set of involved namespaces if the given pipeline is eligible to
* act as a view definition. Otherwise, returns ErrorCodes::OptionNotSupportedOnView.
*/
static StatusWith<stdx::unordered_set<NamespaceString>> validatePipeline(
OperationContext* opCtx, const ViewDefinition& viewDef);
/**
* Reloads the in-memory state of the view catalog from the 'system.views' collection catalog.
* If the 'lookupBehavior' is 'kValidateDurableViews', then the durable view definitions will be
* validated. Reading stops on the first invalid entry with errors logged and returned. Performs
* no cycle detection, etc.
* This is implicitly called by other methods when write operations are performed on the view
* catalog, on external changes to the 'system.views' collection and on the first opening of a
* database.
*/
static Status reload(OperationContext* opCtx,
const Database* db,
ViewCatalogLookupBehavior lookupBehavior);
/**
* Clears the in-memory state of the view catalog.
*/
static void clear(OperationContext* opCtx, const Database* db);
/**
* The view catalog needs to ignore external changes for its own modifications.
*/
static bool shouldIgnoreExternalChange(OperationContext* opCtx,
const Database* db,
const NamespaceString& name);
private:
Status _createOrUpdateView(OperationContext* opCtx,
const NamespaceString& viewName,
const NamespaceString& viewOn,
const BSONArray& pipeline,
std::unique_ptr<CollatorInterface> collator);
/**
* Parses the view definition pipeline, attempts to upsert into the view graph, and refreshes
* the graph if necessary. Returns an error status if the resulting graph would be invalid.
*/
Status _upsertIntoGraph(OperationContext* opCtx, const ViewDefinition& viewDef);
/**
* Returns Status::OK if each view namespace in 'refs' has the same default collation as 'view'.
* Otherwise, returns ErrorCodes::OptionNotSupportedOnView.
*/
Status _validateCollation(OperationContext* opCtx,
const ViewDefinition& view,
const std::vector<NamespaceString>& refs) const;
std::shared_ptr<const ViewDefinition> _lookup(OperationContext* opCtx,
StringData ns,
ViewCatalogLookupBehavior lookupBehavior) const;
std::shared_ptr<ViewDefinition> _lookup(OperationContext* opCtx,
StringData ns,
ViewCatalogLookupBehavior lookupBehavior);
Status _reload(OperationContext* opCtx,
ViewCatalogLookupBehavior lookupBehavior,
bool reloadForCollectionCatalog);
/**
* uasserts with the InvalidViewDefinition error if the current in-memory state of the view
* catalog is invalid. This ensures that calling into the view catalog while it is invalid
* renders it inoperable.
*/
void _requireValidCatalog() const;
ViewMap _viewMap;
std::shared_ptr<DurableViewCatalog> _durable;
bool _valid;
ViewGraph _viewGraph;
bool _viewGraphNeedsRefresh;
Stats _stats;
};
} // namespace mongo
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