title: How to optimize BigQuery queries on a date field where most queries are at a year-month level
body: <p>A question about BigQuery query performance on date fields...</p>
  <p>I have a very large data table where each record has an 'event date' field.  Most of the queries on the table are actually run at a calendar month level, e.g. January 2020 .  Is there any BigQuery performance gain to be had from having an extra field(s) that store either 'year-month' as one field or 'year' and 'month' as two separate extra fields?</p>