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Code Issues Releases Activity

SERVER-17672 Helpers::getSingleton()/getLast() return owned object

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This commit is contained in:
Jason Rassi 2015-03-20 16:51:37 -04:00
parent 3bcc824676
commit 8f931d4443
2 changed files with 29 additions and 19 deletions
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23
src/mongo/db/dbhelpers.cpp
View File

@ -199,19 +199,18 @@ namespace mongo {
return catalog->getIndex(desc)->findSingle( txn, idquery["_id"].wrap() );
}
/* Get the first object from a collection. Generally only useful if the collection
only ever has a single object -- which is a "singleton collection". Note that the
BSONObj returned is *not* owned and will become invalid if the database is closed.
Returns: true if object exists.
*/
bool Helpers::getSingleton(OperationContext* txn, const char *ns, BSONObj& result) {
AutoGetCollectionForRead ctx(txn, ns);
auto_ptr<PlanExecutor> exec(InternalPlanner::collectionScan(txn, ns, ctx.getCollection()));
PlanExecutor::ExecState state = exec->getNext(&result, NULL);
txn->getCurOp()->done();
return PlanExecutor::ADVANCED == state;
if (PlanExecutor::ADVANCED == state) {
result = result.getOwned();
return true;
}
return false;
}
bool Helpers::getLast(OperationContext* txn, const char *ns, BSONObj& result) {
@ -220,9 +219,13 @@ namespace mongo {
ns,
autoColl.getCollection(),
InternalPlanner::BACKWARD));
PlanExecutor::ExecState state = exec->getNext(&result, NULL);
return PlanExecutor::ADVANCED == state;
if (PlanExecutor::ADVANCED == state) {
result = result.getOwned();
return true;
}
return false;
}
void Helpers::upsert( OperationContext* txn,

25
src/mongo/db/dbhelpers.h
View File

@ -107,21 +107,28 @@ namespace mongo {
static RecordId findById(OperationContext* txn,
Collection* collection, const BSONObj& query);
/** Get/put the first (or last) 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 (Context) before calling.
@return true if object exists.
*/
/**
* Get the first object generated from a forward natural-order scan on "ns". Callers do not
* have to lock "ns".
*
* Returns true if there is such an object. An owned copy of the object is placed into the
* out-argument "result".
*
* Returns false if there is no such object.
*/
static bool getSingleton(OperationContext* txn, const char *ns, BSONObj& result);
static void putSingleton(OperationContext* txn, const char *ns, BSONObj obj);
/**
* get last object int he collection; e.g. {$natural : -1}
* Same as getSingleton, but with a reverse natural-order scan on "ns".
*/
static bool getLast(OperationContext* txn, const char *ns, BSONObj& result);
/**
* Performs an upsert of "obj" into the collection "ns", with an empty update predicate.
* Callers must have "ns" locked.
*/
static void putSingleton(OperationContext* txn, const char *ns, BSONObj obj);
/**
* you have to lock
* you do not have to have Context set