support dumping PostgreSQL partitioning options to schema.rb

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Add support for dumping native partitioning table definitions for PostgeSQL adapter
+
+    *Justin Talbott*
+
 *   Make `ActiveRecord::Encryption::Encryptor` agnostic of the serialization format used for encrypted data.
 
     Previously, the encryptor instance only allowed an encrypted value serialized as a `String` to be passed to the message serializer.

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -152,9 +152,14 @@ def indexes(table_name) # :nodoc:
         end
 
         def table_options(table_name) # :nodoc:
+          options = {}
           if comment = table_comment(table_name)
-            { comment: comment }
+            options[:comment] = comment
           end
+          if supports_native_partitioning? && partition_definition = table_partition_definition(table_name)
+            options[:options] = "PARTITION BY #{partition_definition}"
+          end
+          options
         end
 
         # Returns a comment stored in database for given table
@@ -172,6 +177,20 @@ def table_comment(table_name) # :nodoc:
           end
         end
 
+        # Returns the partition definition of a given table
+        def table_partition_definition(table_name) # :nodoc:
+          scope = quoted_scope(table_name, type: "BASE TABLE")
+
+          query_value(<<~SQL, "SCHEMA")
+            SELECT pg_catalog.pg_get_partkeydef(c.oid)
+            FROM pg_catalog.pg_class c
+              LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
+            WHERE c.relname = #{scope[:name]}
+              AND c.relkind IN (#{scope[:type]})
+              AND n.nspname = #{scope[:schema]}
+          SQL
+        end
+
         # Returns the current database name.
         def current_database
           query_value("SELECT current_database()", "SCHEMA")

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -275,6 +275,10 @@ def supports_nulls_not_distinct?
         database_version >= 15_00_00 # >= 15.0
       end
 
+      def supports_native_partitioning?
+        database_version >= 12_00_00 # >= 12.0
+      end
+
       def index_algorithms
         { concurrently: "CONCURRENTLY" }
       end

activerecord/test/cases/adapters/postgresql/schema_test.rb

@@ -832,3 +832,51 @@ def test_nulls_not_set_is_dumped
     assert_no_match(/nulls_not_distinct/, output)
   end
 end
+
+class SchemaPartitionDefinitionsTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+
+  setup do
+    @connection = ActiveRecord::Base.connection
+  end
+
+  teardown do
+    @connection.drop_table "trains", if_exists: true
+  end
+
+  def test_list_partition_options_is_dumped
+    skip("current adapter doesn't support native partitioning") unless supports_native_partitioning?
+
+    @connection.create_table "trains", id: false, options: "PARTITION BY LIST (kind)" do |t|
+      t.string :name
+      t.string :kind
+    end
+
+    output = dump_table_schema "trains"
+
+    assert_match('options: "PARTITION BY LIST (kind)"', output)
+  end
+
+  def test_range_partition_options_is_dumped
+    skip("current adapter doesn't support native partitioning") unless supports_native_partitioning?
+
+    @connection.create_table "trains", id: false, options: "PARTITION BY RANGE (created_at)" do |t|
+      t.string :name
+      t.datetime :created_at, null: false
+    end
+
+    output = dump_table_schema "trains"
+
+    assert_match('options: "PARTITION BY RANGE (created_at)"', output)
+  end
+
+  def test_no_partition_options_are_dumped
+    @connection.create_table "trains" do |t|
+      t.string :name
+    end
+
+    output = dump_table_schema "trains"
+
+    assert_no_match("options:", output)
+  end
+end

activerecord/test/support/adapter_helper.rb

@@ -60,6 +60,7 @@ def supports_text_column_with_default?
     supports_nulls_not_distinct?
     supports_identity_columns?
     supports_virtual_columns?
+    supports_native_partitioning?
   ].each do |method_name|
     define_method method_name do
       ActiveRecord::Base.connection.public_send(method_name)