Question

I’m working on an application that does reporting-type things, and I often need to take a filter specified with JSON, convert that to an SQLAlchemy query, then send the results back to the browser (for example the filter start_date: 1234, end_date: 5678, widget_ids: [1, 2, 3] needs to be converted into the query … WHERE start_date >= 1234 AND end_date <= 5678 AND widget_id in (1, 2, 3)).

Is there a tool which will do this kind of conversion automatically (for example, using suffixes like Django’s ORM: start_date__ge: 1234, end_date__le: 5678, widget_id__in: [1, 2, 3])?

Obviously there would be security and performance implications of such a scheme… But I’d like to know if anything like this exists before I build one myself.

Edit: I realize that I could build my own thing, but I’m specifically wondering if there are existing tools/libraries, so I don’t need to re-invent the wheel.

Answer 1

I have some simple code that may be of interest (source):

def create_attr_filter(request, mapped_class):
    """Create an ``and_`` SQLAlchemy filter (a ClauseList object) based
    on the request params (``queryable``, ``eq``, ``ne``, ...).

    Arguments:

    request
        the request.

    mapped_class
        the SQLAlchemy mapped class.
    """

    mapping = {
        'eq'   : '__eq__',
        'ne'   : '__ne__',
        'lt'   : '__lt__',
        'lte'  : '__le__',
        'gt'   : '__gt__',
        'gte'  : '__ge__',
        'like' : 'like',
        'ilike': 'ilike'
    }
    filters = []
    if 'queryable' in request.params:
        queryable = request.params['queryable'].split(',')
        for k in request.params:
            if len(request.params[k]) <= 0 or '__' not in k:
                continue
            col, op = k.split("__")
            if col not in queryable or op not in mapping.keys():
                continue
            column = getattr(mapped_class, col)
            f = getattr(column, mapping[op])(request.params[k])
            filters.append(f)
    return and_(*filters) if len(filters) > 0 else None