C++ intrusive_ptr::addInitialSource方法代码示例

//.........这里部分代码省略.........
      will already come sorted in the specified order as a result of the
      index scan.
    */
    intrusive_ptr<DocumentSourceSort> sortStage;
    BSONObj sortObj;
    if (!sources.empty()) {
        sortStage = dynamic_cast<DocumentSourceSort*>(sources.front().get());
        if (sortStage) {
            // build the sort key
            sortObj = sortStage->serializeSortKey(/*explain*/ false).toBson();
        }
    }

    // Create the PlanExecutor.
    //
    // If we try to create a PlanExecutor that includes both the match and the
    // sort, and the two are incompatible wrt the available indexes, then
    // we don't get a PlanExecutor back.
    //
    // So we try to use both first.  If that fails, try again, without the
    // sort.
    //
    // If we don't have a sort, jump straight to just creating a PlanExecutor.
    // without the sort.
    //
    // If we are able to incorporate the sort into the PlanExecutor, remove it
    // from the head of the pipeline.
    //
    // LATER - we should be able to find this out before we create the
    // cursor.  Either way, we can then apply other optimizations there
    // are tickets for, such as SERVER-4507.
    const size_t runnerOptions = QueryPlannerParams::DEFAULT |
        QueryPlannerParams::INCLUDE_SHARD_FILTER | QueryPlannerParams::NO_BLOCKING_SORT;
    std::shared_ptr<PlanExecutor> exec;
    bool sortInRunner = false;

    const WhereCallbackReal whereCallback(pExpCtx->opCtx, pExpCtx->ns.db());

    if (sortStage) {
        auto statusWithCQ = CanonicalQuery::canonicalize(
            pExpCtx->ns, queryObj, sortObj, projectionForQuery, whereCallback);

        if (statusWithCQ.isOK()) {
            auto statusWithPlanExecutor = getExecutor(txn,
                                                      collection,
                                                      std::move(statusWithCQ.getValue()),
                                                      PlanExecutor::YIELD_AUTO,
                                                      runnerOptions);
            if (statusWithPlanExecutor.isOK()) {
                // success: The PlanExecutor will handle sorting for us using an index.
                exec = std::move(statusWithPlanExecutor.getValue());
                sortInRunner = true;

                sources.pop_front();
                if (sortStage->getLimitSrc()) {
                    // need to reinsert coalesced $limit after removing $sort
                    sources.push_front(sortStage->getLimitSrc());
                }
            }
        }
    }

    if (!exec.get()) {
        const BSONObj noSort;
        auto statusWithCQ = CanonicalQuery::canonicalize(
            pExpCtx->ns, queryObj, noSort, projectionForQuery, whereCallback);
        uassertStatusOK(statusWithCQ.getStatus());

        exec = uassertStatusOK(getExecutor(txn,
                                           collection,
                                           std::move(statusWithCQ.getValue()),
                                           PlanExecutor::YIELD_AUTO,
                                           runnerOptions));
    }


    // DocumentSourceCursor expects a yielding PlanExecutor that has had its state saved. We
    // deregister the PlanExecutor so that it can be registered with ClientCursor.
    exec->deregisterExec();
    exec->saveState();

    // Put the PlanExecutor into a DocumentSourceCursor and add it to the front of the pipeline.
    intrusive_ptr<DocumentSourceCursor> pSource =
        DocumentSourceCursor::create(fullName, exec, pExpCtx);

    // Note the query, sort, and projection for explain.
    pSource->setQuery(queryObj);
    if (sortInRunner)
        pSource->setSort(sortObj);

    pSource->setProjection(deps.toProjection(), deps.toParsedDeps());

    while (!sources.empty() && pSource->coalesce(sources.front())) {
        sources.pop_front();
    }

    pPipeline->addInitialSource(pSource);

    return exec;
}

        /*
          Execute the pipeline for the explain.  This is common to both the
          locked and unlocked code path.  However, the results are different.
          For an explain, with no lock, it really outputs the pipeline
          chain rather than fetching the data.
         */
        bool executeSplitPipeline(BSONObjBuilder& result, string& errmsg,
                                  const string& ns, const string& db,
                                  intrusive_ptr<Pipeline>& pPipeline,
                                  intrusive_ptr<ExpressionContext>& pCtx) {
            /* setup as if we're in the router */
            pCtx->inRouter = true;

            /*
            Here, we'll split the pipeline in the same way we would for sharding,
            for testing purposes.

            Run the shard pipeline first, then feed the results into the remains
            of the existing pipeline.

            Start by splitting the pipeline.
            */
            intrusive_ptr<Pipeline> pShardSplit = pPipeline->splitForSharded();

            // Write the split pipeline as we would in order to transmit it to the shard servers.
            Document shardCmd = pShardSplit->serialize();

            DEV log() << "\n---- shardDescription\n" << shardCmd.toString() << "\n----\n";

            // for debugging purposes, show what the pipeline now looks like
            DEV log() << "\n---- pipelineDescription\n" << pPipeline->serialize() << "\n----\n";

            /* on the shard servers, create the local pipeline */
            intrusive_ptr<ExpressionContext> pShardCtx =
                new ExpressionContext(InterruptStatusMongod::status, NamespaceString(ns));
            BSONObj shardObj = shardCmd.toBson();
            intrusive_ptr<Pipeline> pShardPipeline(
                Pipeline::parseCommand(errmsg, shardObj, pShardCtx));
            if (!pShardPipeline.get()) {
                return false;
            }

            PipelineD::prepareCursorSource(pShardPipeline, nsToDatabase(ns), pCtx);

            /* run the shard pipeline */
            BSONObjBuilder shardResultBuilder;
            string shardErrmsg;
            pShardPipeline->stitch();
            pShardPipeline->run(shardResultBuilder);
            BSONObj shardResult(shardResultBuilder.done());

            /* pick out the shard result, and prepare to read it */
            intrusive_ptr<DocumentSourceBsonArray> pShardSource;
            BSONObjIterator shardIter(shardResult);
            while(shardIter.more()) {
                BSONElement shardElement(shardIter.next());
                const char *pFieldName = shardElement.fieldName();

                if ((strcmp(pFieldName, "result") == 0) ||
                    (strcmp(pFieldName, "serverPipeline") == 0)) {
                    pPipeline->addInitialSource(DocumentSourceBsonArray::create(&shardElement, pCtx));
                    pPipeline->stitch();

                    /*
                    Connect the output of the shard pipeline with the mongos
                    pipeline that will merge the results.
                    */
                    pPipeline->run(result);
                    return true;
                }
            }

            /* NOTREACHED */
            verify(false);
            return false;
        }