Merge pull request rails#43075 from eileencodes/add-ignore-tables-to-schema-cache

Add ability to ignore tables in the schema cache

Author: eileencodes

activerecord/CHANGELOG.md

@@ -1,3 +1,21 @@
+*   Add config option for ignoring tables when dumping the schema cache.
+
+    Applications can now be configured to ignore certain tables when dumping the schema cache.
+
+    The configuration option can table an array of tables:
+
+    ```ruby
+    config.active_record.schema_cache_ignored_tables = ["ignored_table", "another_ignored_table"]
+    ```
+
+    Or a regex:
+
+    ```ruby
+    config.active_record.schema_cache_ignored_tables = [/^_/]
+    ```
+
+    *Eileen M. Uchitelle*
+
 *   Make schema cache methods return consistent results.
 
     Previously the schema cache methods `primary_keys`, `columns, `columns_hash`, and `indexes`

activerecord/lib/active_record.rb

@@ -170,6 +170,12 @@ module Tasks
   autoload :TestDatabases, "active_record/test_databases"
   autoload :TestFixtures, "active_record/fixtures"
 
+  # A list of tables or regex's to match tables to ignore when
+  # dumping the schema cache. For example if this is set to +[/^_/]+
+  # the schema cache will not dump tables named with an underscore.
+  singleton_class.attr_accessor :schema_cache_ignored_tables
+  self.schema_cache_ignored_tables = []
+
   singleton_class.attr_accessor :legacy_connection_handling
   self.legacy_connection_handling = true
 

activerecord/lib/active_record/connection_adapters/schema_cache.rb

@@ -86,6 +86,7 @@ def primary_keys(table_name)
 
       # A cached lookup for table existence.
       def data_source_exists?(name)
+        return if ignored_table?(name)
         prepare_data_sources if @data_sources.empty?
         return @data_sources[name] if @data_sources.key? name
 
@@ -108,6 +109,10 @@ def data_sources(name)
 
       # Get the columns for a table
       def columns(table_name)
+        if ignored_table?(table_name)
+          raise ActiveRecord::StatementInvalid, "Table '#{table_name}' doesn't exist"
+        end
+
         @columns.fetch(table_name) do
           @columns[deep_deduplicate(table_name)] = deep_deduplicate(connection.columns(table_name))
         end
@@ -166,7 +171,7 @@ def clear_data_source_cache!(name)
 
       def dump_to(filename)
         clear!
-        connection.data_sources.each { |table| add(table) }
+        tables_to_cache.each { |table| add(table) }
         open(filename) { |f|
           if filename.include?(".dump")
             f.write(Marshal.dump(self))
@@ -190,6 +195,18 @@ def marshal_load(array)
       end
 
       private
+        def tables_to_cache
+          connection.data_sources.reject do |table|
+            ignored_table?(table)
+          end
+        end
+
+        def ignored_table?(table_name)
+          ActiveRecord.schema_cache_ignored_tables.any? do |ignored|
+            ignored === table_name
+          end
+        end
+
         def reset_version!
           @version = connection.migration_context.current_version
         end
@@ -216,7 +233,9 @@ def deep_deduplicate(value)
         end
 
         def prepare_data_sources
-          connection.data_sources.each { |source| @data_sources[source] = true }
+          tables_to_cache.each do |source|
+            @data_sources[source] = true
+          end
         end
 
         def open(filename)

activerecord/test/cases/connection_adapters/schema_cache_test.rb

@@ -220,6 +220,43 @@ def test_marshal_dump_and_load_via_disk
         tempfile.unlink
       end
 
+      def test_marshal_dump_and_load_with_ignored_tables
+        old_ignore = ActiveRecord.schema_cache_ignored_tables
+        ActiveRecord.schema_cache_ignored_tables = ["p_schema_migrations"]
+        # Create an empty cache.
+        cache = SchemaCache.new @connection
+
+        tempfile = Tempfile.new(["schema_cache-", ".dump"])
+        # Dump it. It should get populated before dumping.
+        cache.dump_to(tempfile.path)
+
+        # Load a new cache.
+        cache = SchemaCache.load_from(tempfile.path)
+        cache.connection = @connection
+
+        # Assert a table in the cache
+        assert cache.data_sources("posts"), "expected posts to be in the cached data_sources"
+        assert_equal 12, cache.columns("posts").size
+        assert_equal 12, cache.columns_hash("posts").size
+        assert cache.data_sources("posts")
+        assert_equal "id", cache.primary_keys("posts")
+        assert_equal 1, cache.indexes("posts").size
+
+        # Assert ignored table. Behavior should match non-existent table.
+        assert_nil cache.data_sources("p_schema_migrations"), "expected comments to not be in the cached data_sources"
+        assert_raises ActiveRecord::StatementInvalid do
+          cache.columns("p_schema_migrations")
+        end
+        assert_raises ActiveRecord::StatementInvalid do
+          cache.columns_hash("p_schema_migrations").size
+        end
+        assert_nil cache.primary_keys("p_schema_migrations")
+        assert_equal [], cache.indexes("p_schema_migrations")
+      ensure
+        tempfile.unlink
+        ActiveRecord.schema_cache_ignored_tables = old_ignore
+      end
+
       def test_marshal_dump_and_load_with_gzip
         # Create an empty cache.
         cache = SchemaCache.new @connection