Filter only ordinary tables in estimated count (#8913)

* Revert "[deploy] Use max_by instead to get the highest value (#8890)"

This reverts commit b0fb0a484d.

* Only count actual ordinary tables

app/models/application_record.rb

@@ -3,12 +3,15 @@ class ApplicationRecord < ActiveRecord::Base
 
   include Purgeable
 
+  # see <https://www.postgresql.org/docs/11/catalog-pg-class.html> for details
+  # on the `pg_class` table
   QUERY_ESTIMATED_COUNT = <<~SQL.squish.freeze
     SELECT (
       (reltuples / GREATEST(relpages, 1)) *
       (pg_relation_size(?) / (GREATEST(current_setting('block_size')::integer, 1)))
     )::bigint AS count
-    FROM pg_class WHERE relname = ?;
+    FROM pg_class
+    WHERE relname = ? AND relkind = 'r';
   SQL
 
   # Computes an estimated count of the number of rows using stats collected by VACUUM
@@ -18,7 +21,7 @@ class ApplicationRecord < ActiveRecord::Base
     query = sanitize_sql_array([QUERY_ESTIMATED_COUNT, table_name, table_name])
     result = connection.execute(query)
 
-    count = result.max_by(&:values)["count"] # sometimes is an array of hashes, for ex. [{"count" => 0}, [{"count" => 1000}]
+    count = result.first["count"]
     result.clear # PG::Result is manually managed in memory, we need to release its resources
     count
   end