Problem

Using update_resource to bring more source data into a Resource Dataset uses more resources than desired.

Solution

Use the union verb to join the source datasets in a single worksheet before using make_resource to create the Resource Dataset.

Explanation

It is common to build a Resource based on events coming from multiple event Datastreams. It is much more efficient to union the event streams together and do make_resource once. This allows Observe to efficiently align time windows and create an optimal Resource definition.

If you start by using make_resource on one event Datastream and then use update_resource to merge in the other event streams, this will cause an expensive temporal left outer join.

Better:

// I want to build a resource that contains information from three
// event streams. Here the input is dataset evt1.
union @evt2
union @evt3
make_resource options(expiry:1h),
  col1:col1, // from evt1
  col2:col2, // from evt2
  col3:col3, // from evt3
  primary_key(key)

Less Good:

make_resource options(expiry:1h),
  col1:col1,
  primary_key(key)
update_resource options(expiry:1h),
  key=@evt2.key,
  col2:@evt2.col2
update_resource options(expiry:1h),
  key=@evt3.key,
  col3:@evt3.col3