Chain filter conditions dynamically

Question

How to chain multiple conditions in RethinkDB? This is what I got right now and what works if I only pass live or sports as a parameter. As soon as I pass the live and sports parameter, sports obviously always overwrites the filter variable and the live parameter is ignored.

app.get('/bets', function (req, res) {
    var live = req.query.live;
    var sports = req.query.sports;

    var filter = {};

    if (live === undefined) {
        filter = r.or(r.row('live').eq(0), r.row('live').eq(1));
    } else {
        filter.live = parseInt(live);
    }

    if (sports !== undefined) {
        var sports = sports.split(',');
        filter = function (doc) {
            return r.expr(sports).contains(doc("sport"));
        }
    }

    r.table('bets').filter(filter).limit(100).run(connection, function(err, cursor) {
        // ...
    });
});

Still couldn't get it to work, any ideas? – Chris Mar 23 '16 at 14:24 — Chris, Mar 23 '16 at 14:24

nha · Accepted Answer · 2016-03-24T10:34:03.120

You can chain filters with RethinkDB.

Something along the lines of this (warning, untested) :

app.get('/bets', function (req, res) {
    var live = req.query.live;
    var sports = req.query.sports;

    var liveFilter, sportFilter;

    if (live === undefined) {
        liveFilter = r.or(r.row('live').eq(0), r.row('live').eq(1));
    } else {
        liveFilter = function (doc) { return true; };
    }

    if (sports !== undefined) {
        sports = sports.split(','); // no need to redefine the variable here
        sportFilter = function (doc) {
            return r.expr(sports).contains(doc("sport"));
        }
    } else {
         sportFilter = function (doc) { return true; };
    }

    r.table('bets')
     .filter(liveFilter)     // apply the first filter
     .filter(sportsFilter)   // apply the second filter
     .limit(100)
     .run(connection, function(err, cursor) {
        // ...
    });
});

Alternatively you could make one filter function that would handle both the live and sport filters (equally untested, this is to get you started) :

app.get('/bets', function (req, res) {
    var live = req.query.live;
    var sports = req.query.sports.split(',');

    var filter = function(doc){
      var sportPass, livePass;

        if (live === undefined) {
            livePass = r.or(r.row('live').eq(0), r.row('live').eq(1))(doc);
        } else {
            livePass = parseInt(live); // not sure what you meant by filter.live here
        }

        if (sports !== undefined) {
            sportPass = r.expr(sports).contains(doc("sport"));
        }

        return sportPass && livePass;
    };


    r.table('bets').filter(filter).limit(100).run(connection, function(err, cursor) {
        // ...
    });
});

Chain filter conditions dynamically

1 Answers1