Channels: Migration to add materialized column, backfill code (#4798)

* Channels: Migration to add column, backfill code

This change adds `acqusition_channel` columns to events_v2 and
sessions_v2 tables. These columns are materialized - we don't ingest
into them directly. Instead they're calculated based on other columns.

The data migration changes now allow to also backfill the column.

Tested the ability to change definitions by changing the function
definitions and re-running the migration with backfill. Confirmed that
the underlying data changed as expected.

* quiet option

* Exclude data migrations from validation

* Migration consistency

.github/workflows/migrations-validation.yml

@@ -16,13 +16,17 @@ jobs:
       id: changes
       with:
         list-files: json
+        predicate-quantifier: 'every'
         filters: |
           lib:
             - 'lib/**'
+            - '!lib/plausible/data_migration/**'
+          extra:
             - 'extra/**'
+          config:
             - 'config/**'
 
-    - if: steps.changes.outputs.lib == 'true'
+    - if: steps.changes.outputs.lib == 'true' || steps.changes.outputs.extra == 'true' || steps.changes.outputs.config == 'true'
       run: |
         echo "::error file=${{ fromJSON(steps.changes.outputs.lib_files)[0] }}::Code and migrations shouldn't be changed at the same time"
         exit 1

lib/plausible/data_migration/acquisition_channel.ex

@@ -2,6 +2,15 @@ defmodule Plausible.DataMigration.AcquisitionChannel do
   @moduledoc """
   Creates dictionaries and functions to calculate acquisition channel in ClickHouse
 
+  Creates `acquisition_channel` columns in `events_v2` and `sessions_v2` tables.
+  Run via `Plausible.DataMigration.AcquisitionChannel.run(options)`
+
+  Options:
+  - `add_column` - creates the materialized column. Already done in a migration
+  - `update_column` - Updates the column definition to use new function definitions. Defaults to true.
+      Note that historical data is only updated if `backfill` is set to true or if it was never materialized.
+  - `backfill` - backfills the data for the column. Speeds up calculations on historical data.
+
   SQL files available at: priv/data_migrations/AcquisitionChannel/sql
   """
   use Plausible.DataMigration, dir: "AcquisitionChannel", repo: Plausible.IngestRepo
@@ -11,6 +20,7 @@ defmodule Plausible.DataMigration.AcquisitionChannel do
     # In distributed environments, wait for insert to all temporary tables.
     insert_quorum = Plausible.IngestRepo.replica_count("sessions_v2")
 
+    :ok =
       run_sql_multi(
         "acquisition_channel_functions",
         [
@@ -25,5 +35,56 @@ defmodule Plausible.DataMigration.AcquisitionChannel do
         },
         quiet: Keyword.get(opts, :quiet, false)
       )
+
+    cond do
+      Keyword.get(opts, :add_column) ->
+        alter_data_tables(
+          "acquisition_channel_add_materialized_column",
+          on_cluster_statement,
+          opts
+        )
+
+      Keyword.get(opts, :update_column, true) ->
+        alter_data_tables(
+          "acquisition_channel_update_materialized_column",
+          on_cluster_statement,
+          opts
+        )
+
+      true ->
+        nil
+    end
+
+    if Keyword.get(opts, :backfill) do
+      alter_data_tables(
+        "acquisition_channel_backfill_materialized_column",
+        on_cluster_statement,
+        opts
+      )
+    end
+
+    :ok
+  end
+
+  defp alter_data_tables(sql_name, on_cluster_statement, opts) do
+    {:ok, _} =
+      run_sql(
+        sql_name,
+        [
+          table: "events_v2",
+          on_cluster_statement: on_cluster_statement
+        ],
+        quiet: Keyword.get(opts, :quiet, false)
+      )
+
+    {:ok, _} =
+      run_sql(
+        sql_name,
+        [
+          table: "sessions_v2",
+          on_cluster_statement: on_cluster_statement
+        ],
+        quiet: Keyword.get(opts, :quiet, false)
+      )
   end
 end

priv/data_migrations/AcquisitionChannel/sql/acquisition_channel_add_materialized_column.sql.eex

@@ -0,0 +1,4 @@
+ALTER TABLE <%= @table %>
+<%= @on_cluster_statement %>
+ADD COLUMN IF NOT EXISTS acquisition_channel LowCardinality(String)
+MATERIALIZED acquisition_channel(referrer_source, utm_medium, utm_campaign, utm_source, click_id_param)

priv/data_migrations/AcquisitionChannel/sql/acquisition_channel_backfill_materialized_column.sql.eex

@@ -0,0 +1,2 @@
+ALTER TABLE <%= @table %>
+MATERIALIZE COLUMN acquisition_channel

priv/data_migrations/AcquisitionChannel/sql/acquisition_channel_functions.sql.eex

@@ -11,7 +11,7 @@ ENGINE = MergeTree()
 <% end %>
 ORDER BY referrer_source;
 
-TRUNCATE TABLE acquisition_channel_source_category SETTINGS alter_sync=2;
+TRUNCATE TABLE acquisition_channel_source_category <%= @on_cluster_statement %>;
 
 INSERT INTO acquisition_channel_source_category(referrer_source, category)
 SELECT t.1 AS referrer_source, t.2 AS category
@@ -43,7 +43,7 @@ ENGINE = MergeTree()
 <% end %>
 ORDER BY referrer_source;
 
-TRUNCATE TABLE acquisition_channel_paid_sources SETTINGS alter_sync=2;
+TRUNCATE TABLE acquisition_channel_paid_sources <%= @on_cluster_statement %>;
 
 INSERT INTO acquisition_channel_paid_sources(referrer_source)
 SELECT arrayJoin({paid_sources:Array(String)}) AS referrer_source

priv/data_migrations/AcquisitionChannel/sql/acquisition_channel_update_materialized_column.sql.eex

@@ -0,0 +1,4 @@
+ALTER TABLE <%= @table %>
+<%= @on_cluster_statement %>
+MODIFY COLUMN acquisition_channel LowCardinality(String)
+MATERIALIZED acquisition_channel(referrer_source, utm_medium, utm_campaign, utm_source, click_id_param)

priv/ingest_repo/migrations/20241111084056_create_acquisition_channel_column.exs

@@ -0,0 +1,11 @@
+defmodule Plausible.IngestRepo.Migrations.CreateAcquisitionChannelColumn do
+  use Ecto.Migration
+
+  def up do
+    Plausible.DataMigration.AcquisitionChannel.run(add_column: true, backfill: false)
+  end
+
+  def down do
+    raise "irreversible"
+  end
+end