Fix merge conflict in postgresql_adapter_test, update README with new configuration setting

Author: keithdoggett

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## 6.1.0-beta.3 - 2021-04-02
+
+- Added a configuration option named `use_follower_reads_for_type_introspection`.
+  If true, it improves the speed of type introspection by allowing potentially stale
+  type metadata to be read. Defaults to false.
+
 ## 6.1.0-beta.2 - 2021-03-06
 
 - Improved connection performance by refactoring an introspection

README.md

@@ -22,6 +22,13 @@ development:
   user: <username>
 ```
 
+## Configuration
+
+In addition to the standard adapter settings, CockroachDB also supports the following:
+
+- `use_follower_reads_for_type_introspection`: Use follower reads on queries to the `pg_type` catalog when set to `true`. This helps to speed up initialization by reading historical data, but may not find recently created user-defined types.
+- `disable_cockroachdb_telemetry`: Determines if a telemetry call is made to the database when the connection pool is initialized. Setting this to `true` will prevent the call from being made.
+
 ## Working with Spatial Data
 
 The adapter uses [RGeo](https://github.com/rgeo/rgeo) and [RGeo-ActiveRecord](https://github.com/rgeo/rgeo-activerecord) to represent geometric and geographic data as Ruby objects and easily interface them with the adapter. The following is a brief introduction to RGeo and tips to help setup your spatial application. More documentation about RGeo can be found in the [YARD Docs](https://rubydoc.info/github/rgeo/rgeo) and [wiki](https://github.com/rgeo/rgeo/wiki).

activerecord-cockroachdb-adapter.gemspec

@@ -4,7 +4,7 @@ $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 
 Gem::Specification.new do |spec|
   spec.name          = "activerecord-cockroachdb-adapter"
-  spec.version       = "6.1.0-beta.2"
+  spec.version       = "6.1.0-beta.3"
   spec.licenses      = ["Apache-2.0"]
   spec.authors       = ["Cockroach Labs"]
   spec.email         = ["[email protected]"]

lib/active_record/connection_adapters/cockroachdb_adapter.rb

@@ -469,6 +469,97 @@ def is_cached_plan_failure?(e)
           false
         end
 
+        # override
+        # This method loads info about data types from the database to
+        # populate the TypeMap.
+        #
+        # Currently, querying from the pg_type catalog can be slow due to geo-partitioning
+        # so this modified query uses AS OF SYSTEM TIME '-10s' to read historical data.
+        def load_additional_types(oids = nil)
+          if @config[:use_follower_reads_for_type_introspection]
+            initializer = OID::TypeMapInitializer.new(type_map)
+
+            query = <<~SQL
+              SELECT t.oid, t.typname, t.typelem, t.typdelim, t.typinput, r.rngsubtype, t.typtype, t.typbasetype
+              FROM pg_type as t
+              LEFT JOIN pg_range as r ON oid = rngtypid AS OF SYSTEM TIME '-10s'
+            SQL
+
+            if oids
+              query += "WHERE t.oid IN (%s)" % oids.join(", ")
+            else
+              query += initializer.query_conditions_for_initial_load
+            end
+
+            execute_and_clear(query, "SCHEMA", []) do |records|
+              initializer.run(records)
+            end
+          else
+            super
+          end
+        rescue ActiveRecord::StatementInvalid => e
+          raise e unless e.cause.is_a? PG::InvalidCatalogName
+          # use original if database is younger than 10s
+          super
+        end
+
+        # override
+        # This method maps data types to their proper decoder.
+        #
+        # Currently, querying from the pg_type catalog can be slow due to geo-partitioning
+        # so this modified query uses AS OF SYSTEM TIME '-10s' to read historical data.
+        def add_pg_decoders
+          if @config[:use_follower_reads_for_type_introspection]
+            @default_timezone = nil
+            @timestamp_decoder = nil
+
+            coders_by_name = {
+              "int2" => PG::TextDecoder::Integer,
+              "int4" => PG::TextDecoder::Integer,
+              "int8" => PG::TextDecoder::Integer,
+              "oid" => PG::TextDecoder::Integer,
+              "float4" => PG::TextDecoder::Float,
+              "float8" => PG::TextDecoder::Float,
+              "numeric" => PG::TextDecoder::Numeric,
+              "bool" => PG::TextDecoder::Boolean,
+              "timestamp" => PG::TextDecoder::TimestampUtc,
+              "timestamptz" => PG::TextDecoder::TimestampWithTimeZone,
+            }
+
+            known_coder_types = coders_by_name.keys.map { |n| quote(n) }
+            query = <<~SQL % known_coder_types.join(", ")
+              SELECT t.oid, t.typname
+              FROM pg_type as t AS OF SYSTEM TIME '-10s'
+              WHERE t.typname IN (%s)
+            SQL
+
+            coders = execute_and_clear(query, "SCHEMA", []) do |result|
+              result
+                .map { |row| construct_coder(row, coders_by_name[row["typname"]]) }
+                .compact
+            end
+
+            map = PG::TypeMapByOid.new
+            coders.each { |coder| map.add_coder(coder) }
+            @connection.type_map_for_results = map
+
+            @type_map_for_results = PG::TypeMapByOid.new
+            @type_map_for_results.default_type_map = map
+            @type_map_for_results.add_coder(PG::TextDecoder::Bytea.new(oid: 17, name: "bytea"))
+            @type_map_for_results.add_coder(MoneyDecoder.new(oid: 790, name: "money"))
+
+            # extract timestamp decoder for use in update_typemap_for_default_timezone
+            @timestamp_decoder = coders.find { |coder| coder.name == "timestamp" }
+            update_typemap_for_default_timezone
+          else
+            super
+          end
+        rescue ActiveRecord::StatementInvalid => e
+          raise e unless e.cause.is_a? PG::InvalidCatalogName
+          # use original if database is younger than 10s
+          super
+        end
+
         def arel_visitor
           Arel::Visitors::CockroachDB.new(self)
         end

test/cases/adapters/postgresql/postgresql_adapter_test.rb

@@ -16,7 +16,7 @@ def setup
       end
 
       def teardown
-        # use connection without follower_reads
+        # use connection without follower_reads and telemetry
         database_config = { "adapter" => "cockroachdb", "database" => "activerecord_unittest" }
         ar_config = ActiveRecord::Base.configurations.configs_for(env_name: "arunit", name: "primary")
         database_config.update(ar_config.configuration_hash)
@@ -50,6 +50,18 @@ def test_using_telemetry_builtin_connects_properly
 
         assert_equal(false, conn_config[:disable_cockroachdb_telemetry])
       end
+
+      def test_using_follower_reads_connects_properly
+        database_config = { "use_follower_reads_for_type_introspection": true, "adapter" => "cockroachdb", "database" => "activerecord_unittest" }
+        ar_config = ActiveRecord::Base.configurations.configs_for(env_name: "arunit", name: "primary")
+        database_config.update(ar_config.configuration_hash)
+
+        ActiveRecord::Base.establish_connection(database_config)
+        conn = ActiveRecord::Base.connection
+        conn_config = conn.instance_variable_get("@config")
+
+        assert conn_config[:use_follower_reads_for_type_introspection]
+      end
     end
   end
 end