Status ModifierInc::prepare(mutablebson::Element root,
StringData matchedField,
ExecInfo* execInfo) {
_preparedState.reset(new PreparedState(root.getDocument()));
// If we have a $-positional field, it is time to bind it to an actual field part.
if (_posDollar) {
if (matchedField.empty()) {
return Status(ErrorCodes::BadValue,
str::stream() << "The positional operator did not find the match "
"needed from the query. Unexpanded update: "
<< _fieldRef.dottedField());
}
_fieldRef.setPart(_posDollar, matchedField);
}
// Locate the field name in 'root'. Note that we may not have all the parts in the path
// in the doc -- which is fine. Our goal now is merely to reason about whether this mod
// apply is a noOp or whether is can be in place. The remaining path, if missing, will
// be created during the apply.
Status status = pathsupport::findLongestPrefix(_fieldRef,
root,
&_preparedState->idxFound,
&_preparedState->elemFound);
// FindLongestPrefix may say the path does not exist at all, which is fine here, or
// that the path was not viable or otherwise wrong, in which case, the mod cannot
// proceed.
if (status.code() == ErrorCodes::NonExistentPath) {
_preparedState->elemFound = root.getDocument().end();
}
else if (!status.isOK()) {
return status;
}
// We register interest in the field name. The driver needs this info to sort out if
// there is any conflict among mods.
execInfo->fieldRef[0] = &_fieldRef;
// Capture the value we are going to write. At this point, there may not be a value
// against which to operate, so the result will be simply _val.
_preparedState->newValue = _val;
//
// in-place and no-op logic
//
// If the field path is not fully present, then this mod cannot be in place, nor is a
// noOp.
if (!_preparedState->elemFound.ok() ||
_preparedState->idxFound < (_fieldRef.numParts() - 1)) {
// For multiplication, we treat ops against missing as yielding zero. We take
// advantage here of the promotion rules for SafeNum; the expression below will
// always yield a zero of the same type of operand that the user provided
// (e.g. double).
if (_mode == MODE_MUL)
_preparedState->newValue *= SafeNum(static_cast<int>(0));
return Status::OK();
}
// If the value being $inc'ed is the same as the one already in the doc, than this is a
// noOp.
if (!_preparedState->elemFound.isNumeric()) {
mb::Element idElem = mb::findFirstChildNamed(root, "_id");
return Status(
ErrorCodes::TypeMismatch,
str::stream() << "Cannot apply "
<< (_mode == MODE_INC ? "$inc" : "$mul")
<< " to a value of non-numeric type. {"
<< idElem.toString()
<< "} has the field '" << _preparedState->elemFound.getFieldName()
<< "' of non-numeric type "
<< typeName(_preparedState->elemFound.getType()));
}
const SafeNum currentValue = _preparedState->elemFound.getValueSafeNum();
// Update newValue w.r.t to the current value of the found element.
if (_mode == MODE_INC)
_preparedState->newValue += currentValue;
else
_preparedState->newValue *= currentValue;
// If the result of the addition is invalid, we must return an error.
if (!_preparedState->newValue.isValid()) {
mb::Element idElem = mb::findFirstChildNamed(root, "_id");
return Status(ErrorCodes::BadValue,
str::stream() << "Failed to apply $inc operations to current value ("
<< currentValue.debugString() << ") for document {"
<< idElem.toString() << "}");
}
// If the values are identical (same type, same value), then this is a no-op.
if (_preparedState->newValue.isIdentical(currentValue)) {
_preparedState->noOp = execInfo->noOp = true;
return Status::OK();
}
return Status::OK();
}