动态构建rethinkdb查询-python

Question

I'm trying to build a rethinkdb query server-side, dynamically. The end goal is to have queries that are structured approximately like this (in javascript):

r.db('test').table('data')
.filter(function (row) {
  return row('subgroup').eq('x').or(row('subgroup').eq('y'))
  .and(
    .row('metric_id').eq('a')
    .or(row('metric_id).eq('b')
    .or(row('metric_id').eq('c'))
})

I need to pass in a set of keys, each with a set of acceptable values. For the above example, I'd pass in

{
  'subgroup': ['x', 'y'],
  'metric_id': ['a', 'b', 'c']
}

The query should return all records for which subgroup is x OR y AND metric_id is a OR b OR c .

I'm struggling with the correct way to do this. See one attempt below:

def parse_filters(cls, filters):
    def rethink_filter(data):
        result = r.expr(True) # initialize filter function
        for key in filters:
            or_statements = []
            for value in filters[key]:
                f = {}
                f[key] = value
                or_statements.append(r.expr(f)) # build a list of 
            result = result.and_(r.or_(r.expr(or_statements)))
            if not result:
                break
        return result

    return rethink_filter

With the input of

{
  'entity_id': ['a', 'b'],
  'metric_id': ['x']
}

rethink_filter gives the query:

r.and_(r.and_(True, r.or_([{'entity_id': 'a'}, {'entity_id': 'b'}])), r.or_([{'metric_id': 'x'}]))

which looks like it ought to give the results I'm after, but it returns all items in the table, regardless of entity_id or metric_id .

Where am I going wrong?

Answer 1

r.or can be used as an infix operator, or all of the arguments can be provided as parameters . You are passing in only a single parameter: an array.

Since an array always evaluated to True, this query:

r.and_(r.and_(True, r.or_([{'entity_id': 'a'}, {'entity_id': 'b'}])), r.or_([{'metric_id': 'x'}]))

effectively becomes:

r.and_(r.and_(True, r.or_(True)), r.or_(True))

Which I hope you can see will evaluate to True for every record.

When you need to pass an array to a function in RethinkDB that expects parameters, you can use r.args .

You will also not be able to use the dictionary shorthand inside of an r.or function. That is, instead of { 'entity_id' : 'a' } you will need to translate those into document['entity_id'] == 'a' I believe. You can get access to the document through a lambda function, see the examples on the filter documentation .