## Is your feature request related to a problem?

There's only 2 files where we use pandas, but pandas is 49MB and numpy is another 86MB, slowing down builds massively.

## Describe the solution you'd like

Replace pandas with a pure SQL/Python solution in
- posthog/queries/trends.py
- posthog/queries/sessions.py

Both of those have equivalent examples in Clickhouse (ee/clickhouse) that don't use Pandas.

## Describe alternatives you've considered

Continue using Pandas and clogging builds

## Additional context



#### *Thank you* for your feature request – we love each and every one!

posthog/queries/test/test_trends.py
"2020-11-05",
                            "2020-11-06",
                            "2020-11-07",
                            "2020-11-08",
                            "2020-11-09",
                            "2020-11-10",
                            "2020-11-11",
                            "2020-11-12",
                            "2020-11-13",
                            "2020-11-14",
                        ],
                    }
                ],
            )
        def test_last30days_timerange(self):
            self._test_events_with_dates(
                dates=[
                    "2020-11-01 05:20:00",
                    "2020-11-11 10:22:00",
                    "2020-11-24 10:25:00",
                    "2020-11-05 08:25:00",
                    "2020-11-05 08:25:00",
                    "2020-11-10 08:25:00",
                ],
                date_from="-30d",
                interval="week",
                query_time="2020-11-30 10:20:00",
                result=[
                    {
                        "action": {