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+---
+stage: Growth
+group: Product Intelligence
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
+---
+
+# Usage Data Metrics guide
+
+This guide describes deprecated usage for metrics in `usage_data.rb`.
+
+NOTE:
+Implementing metrics direct in `usage_data.rb` is deprecated, We recommend you use [instrumentation classes](metrics_instrumentation.md).
+
+## Ordinary batch counters
+
+Simple count of a given `ActiveRecord_Relation`, does a non-distinct batch count, smartly reduces `batch_size`, and handles errors.
+Handles the `ActiveRecord::StatementInvalid` error.
+
+Method:
+
+```ruby
+count(relation, column = nil, batch: true, start: nil, finish: nil)
+```
+
+Arguments:
+
+- `relation` the ActiveRecord_Relation to perform the count
+- `column` the column to perform the count on, by default is the primary key
+- `batch`: default `true` to use batch counting
+- `start`: custom start of the batch counting to avoid complex min calculations
+- `end`: custom end of the batch counting to avoid complex min calculations
+
+Examples:
+
+```ruby
+count(User.active)
+count(::Clusters::Cluster.aws_installed.enabled, :cluster_id)
+count(::Clusters::Cluster.aws_installed.enabled, :cluster_id, start: ::Clusters::Cluster.minimum(:id), finish: ::Clusters::Cluster.maximum(:id))
+```
+
+## Distinct batch counters
+
+Distinct count of a given `ActiveRecord_Relation` on given column, a distinct batch count, smartly reduces `batch_size`, and handles errors.
+Handles the `ActiveRecord::StatementInvalid` error.
+
+Method:
+
+```ruby
+distinct_count(relation, column = nil, batch: true, batch_size: nil, start: nil, finish: nil)
+```
+
+Arguments:
+
+- `relation`: the ActiveRecord_Relation to perform the count
+- `column`: the column to perform the distinct count, by default is the primary key
+- `batch`: default `true` to use batch counting
+- `batch_size`: if none set it uses default value 10000 from `Gitlab::Database::BatchCounter`
+- `start`: custom start of the batch counting to avoid complex min calculations
+- `end`: custom end of the batch counting to avoid complex min calculations
+
+WARNING:
+Counting over non-unique columns can lead to performance issues. For more information, see the [iterating tables in batches](../iterating_tables_in_batches.md) guide.
+
+Examples:
+
+```ruby
+distinct_count(::Project, :creator_id)
+distinct_count(::Note.with_suggestions.where(time_period), :author_id, start: ::User.minimum(:id), finish: ::User.maximum(:id))
+distinct_count(::Clusters::Applications::CertManager.where(time_period).available.joins(:cluster), 'clusters.user_id')
+```