A number of stages track whether their child is open via a _childOpened boolean flag. This flag is usually set after calling open() on the child. For example:

    // From FilterStage.
    void open(bool reOpen) final {
        // <Other logic omitted>
        _children[0]->open(reOpen);// This might throw!
        _childOpened = true;
    } 

Unfortunately, a call to open() may throw, in order to abort a trial period. If this happens, the stage's _childOpened flag is never set to true. This means that a call to close() on the parent stage will not result in the child stage being closed.

    // FilterStage.
    void close() final {
        // <Omitted>
        if (_childOpened) {
            // This branch isn't taken if the exception is thrown on open().
            _children[0]->close();
            _childOpened = false;
        }
    } 

In other words, after the exception is thrown, even closing() and opening() the plan leaves the tree in an invalid state. Attempting to use the plan may result in a server crash.

We should do a full audit of all of the SBE stages and make sure this pattern is fixed in every case. Here are the two places I've encountered it:

https://github.com/mongodb/mongo/blob/fbe42b59f77c645413ebb60f6d11df7acf9612ee/src/mongo/db/exec/sbe/stages/filter.h#L98-L99

https://github.com/mongodb/mongo/blob/fbe42b59f77c645413ebb60f6d11df7acf9612ee/src/mongo/db/exec/sbe/stages/hash_agg.cpp#L167-L168