intrusive_ptr<DocumentSource> DocumentSourceGroup::createMerger() {
intrusive_ptr<DocumentSourceGroup> pMerger(
DocumentSourceGroup::create(pCtx));
/* the merger will use the same grouping key */
pMerger->setIdExpression(ExpressionFieldPath::create(
Document::idName.c_str()));
const size_t n = vFieldName.size();
for(size_t i = 0; i < n; ++i) {
/*
The merger's output field names will be the same, as will the
accumulator factories. However, for some accumulators, the
expression to be accumulated will be different. The original
accumulator may be collecting an expression based on a field
expression or constant. Here, we accumulate the output of the
same name from the prior group.
*/
pMerger->addAccumulator(
vFieldName[i], vpAccumulatorFactory[i],
ExpressionFieldPath::create(vFieldName[i]));
}
return pMerger;
}
intrusive_ptr<DocumentSource> DocumentSourceGroup::getRouterSource() {
intrusive_ptr<ExpressionContext> pMergerExpCtx = pExpCtx->clone();
pMergerExpCtx->setDoingMerge(true);
intrusive_ptr<DocumentSourceGroup> pMerger(DocumentSourceGroup::create(pMergerExpCtx));
/* the merger will use the same grouping key */
pMerger->setIdExpression(ExpressionFieldPath::parse("$$ROOT._id"));
const size_t n = vFieldName.size();
for(size_t i = 0; i < n; ++i) {
/*
The merger's output field names will be the same, as will the
accumulator factories. However, for some accumulators, the
expression to be accumulated will be different. The original
accumulator may be collecting an expression based on a field
expression or constant. Here, we accumulate the output of the
same name from the prior group.
*/
pMerger->addAccumulator(
vFieldName[i], vpAccumulatorFactory[i],
ExpressionFieldPath::parse("$$ROOT." + vFieldName[i]));
}
return pMerger;
}
