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// dbhelpers.h
/**
* Copyright (C) 2008 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/* db helpers are helper functions and classes that let us easily manipulate the local
database instance.
*/
#pragma once
namespace mongo {
struct Helpers {
/* ensure the specified index exists.
@param keyPattern key pattern, e.g., { ts : 1 }
@param name index name, e.g., "name_1"
This method can be a little (not much) cpu-slow, so you may wish to use
OCCASIONALLY ensureIndex(...);
Note: use ensureHaveIdIndex() for the _id index: it is faster.
Note: does nothing if collection does not yet exist.
*/
static void ensureIndex(const char *ns, BSONObj keyPattern, const char *name);
/* fetch a single object from collection ns that matches query.
set your db context first.
@param requireIndex if true, complain if no index for the query. a way to guard against
writing a slow query.
@return true if object found
*/
static bool findOne(const char *ns, BSONObj query, BSONObj& result, bool requireIndex = false);
/* Get/put the first object from a collection. Generally only useful if the collection
only ever has a single object -- which is a "singleton collection".
You do not need to set the database before calling.
Returns: true if object exists.
*/
static bool getSingleton(const char *ns, BSONObj& result);
static void putSingleton(const char *ns, BSONObj obj);
/* Remove all objects from a collection.
You do not need to set the database before calling.
*/
static void emptyCollection(const char *ns);
};
/* Set database we want to use, then, restores when we finish (are out of scope)
Note this is also helpful if an exception happens as the state if fixed up.
*/
class DBContext {
Database *old;
public:
DBContext(const char *ns) {
old = database;
setClientTempNs(ns);
}
DBContext(string ns) {
old = database;
setClientTempNs(ns.c_str());
}
~DBContext() {
database = old;
}
};
} // namespace mongo
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