add presto dttm format in dttm_converter

[tarekrached]

Presto doesn't understand ISO 8601 timestamp strings as time-like, so currently, timestamp comparisons in Presto are being executed as lexical varchar comparisons.

This means that TIMESTAMP columns in Presto can't be used as dttm columns. If you do try to use a TIMESTAMP column in Presto as a dttm column, you get a GREATER_THAN_OR_EQUAL(timestamp, varchar) not registered

One solution would be to add a Presto-specific dttm_converter, such as

"CAST('{}' AS TIMESTAMP)".format(dttm.strftime('%Y-%m-%d %H:%M:%S.%f')[:-3]))

This approach was initially proposed in #522, but I'm creating this issue so that we can discuss more broadly.
#506 (or a per-column version) is necessary but not sufficient - if & when it it gets merged, the timestamp comparison with still be performed as a lexical string comparisons in Presto, and that is not going to work for date formats such as MM/DD/YYYY. (e.g. 01/01/2001 < 02/01/2000).

Whatever solution we end up with should not hinder Presto's optimizer from partition pruning and index utilization.

[mistercrunch]

We now support per-column spec for how to handle date time, it will be in the next release.

[tarekrached]

Thanks again for your work on this, @mistercrunch!