title: Do you need to add an index on a partitioned table (postgres 11)?
body: <p>My team is looking at moving our non partitioned table with ~1TB of data over to a partitioned table.</p>
  
  <p>We would be using range partitioning based on a timestamp column.</p>
  
  <p>One thing I don't understand is whether we need to add an index on the timestamp column if it's being used as the partition key. If we make our partitions quite small (e.g. partition for every day), would this act in a similar way to an index?</p>
  
  <p>We would only be doing queries on a maximum resolution of one day.</p>
  
  <p>I am reluctant to add an index as we've tried this in the past and it never completed (probably because we didn't turn off writes. Not really an option to turn off writes for an extended period).</p>