Adjusted to properly type each of the database interactions

lib/mixer/metrics/buffer.ex

@@ -128,14 +128,18 @@ defmodule Mixer.Metrics.Buffer do
 
   defp do_flush(events) do
     rows = Enum.reverse(events)
+    count = length(rows)
 
     try do
-      {count, _} = Mixer.ClickhouseRepo.insert_all(PostEvent, rows)
+      # ClickHouse async inserts acknowledge writes immediately and always
+      # return num_rows: 0 — the data is queued for background commitment.
+      # We use our own row count for the log so it is always accurate.
+      Mixer.ClickhouseRepo.insert_all(PostEvent, rows)
       Logger.debug("[Mixer.Metrics.Buffer] Flushed #{count} event(s) to ClickHouse")
     rescue
       error ->
         Logger.error(
-          "[Mixer.Metrics.Buffer] Failed to flush #{length(rows)} event(s) to ClickHouse: " <>
+          "[Mixer.Metrics.Buffer] Failed to flush #{count} event(s) to ClickHouse: " <>
             Exception.message(error)
         )
     end

lib/mixer/metrics/post_event.ex

@@ -22,19 +22,23 @@ defmodule Mixer.Metrics.PostEvent do
   @primary_key false
 
   schema "post_events" do
-    # LowCardinality(String) in ClickHouse — keep values in the set above
-    field :event_type, :string
+    # Must be Ch-typed so ecto_ch emits LowCardinality(String) in the RowBinary
+    # header, matching the ClickHouse table DDL exactly.
+    field :event_type, Ch, type: "LowCardinality(String)"
 
     # The tweet that the event relates to
     field :tweet_id, Ecto.UUID
 
-    # The acting user; may be nil for anonymous views
-    field :user_id, Ecto.UUID
+    # The acting user; may be nil for anonymous views.
+    # Must be Ch-typed so ecto_ch emits Nullable(UUID) in the RowBinary header,
+    # matching the ClickHouse table DDL exactly.
+    field :user_id, Ch, type: "Nullable(UUID)"
 
     # Wall-clock time of the event (UTC, second precision)
     field :occurred_at, :utc_datetime
 
-    # Optional originating IP, useful for deduplicating anonymous views
-    field :ip_address, :string
+    # Optional originating IP, useful for deduplicating anonymous views.
+    # Nullable(String) for the same reason as user_id above.
+    field :ip_address, Ch, type: "Nullable(String)"
   end
 end