adding comment on migration to explain how often cagg refresh policie…

…s are run and how far they look back

db/migrate/20231106170457_add_continuous_aggregate_refresh_policies.rb

@@ -1,5 +1,17 @@
 # frozen_string_literal: true
 
+# These refresh policies have a start_offset of 3 days, because that is the smallest possible starting offset (anything smaller will get a `refresh window is too small` db error)
+# These refresh policies will look back at the associated tables (classification_events, comment_events, or classification_user_groups) for the past 3 days through the last hour of when the refresh job is run, and re-compute the continuous aggregate.
+
+# These refresh policies run everyday, if we want to change the frequency refresh policies are run, we will need to update the `scheduling_interval` of the refresh policy
+
+# Eg.
+#
+# Refresh Continuous Aggregate Job is run today Nov 6th 1:47PM CST, the job will look at the classification_events table for the past 3 days (Nov 3rd) through the past hour (Nov 6th 12:47 PM CST), and will check for any changes in the classification_events table that have NOT been calculated in previous refresh jobs and then update the caggs with updated calculations.
+
+# More on refresh policies for continuous aggregates found here:
+# https://docs.timescale.com/api/latest/continuous-aggregates/add_continuous_aggregate_policy/
+
 class AddContinuousAggregateRefreshPolicies < ActiveRecord::Migration[7.0]
   # we have to disable the migration transaction because creating materialized views within it is not allowed.
   disable_ddl_transaction!