I have a query as follows:

select count(*) from githubEvents where dateTrunc('YEAR', event_time) = '2016-01-01 00:00:00.0'

It produces a nonzero result:

However, when I try an explain plan:

explain plan for select count(*) from githubEvents where dateTrunc('YEAR', event_time) = '2016-01-01 00:00:00.0'

The query plan picks a segment at random which should have been pruned, and doesn't reflect the way the query is evaluated:

It would be helpful if the plan chose a segment which has data, or queried all segments and merged operators when the operator varies according to segment.