Minimal RelationTracker (tracking RelationMessage) with further exten…

…sibility for oid caching.

CHANGELOG.md

@@ -6,6 +6,7 @@
 - `TypeCodec` interface is used for encoding/decoding value by OIDs.
   Gets a reference to `TypeCodecContext` which contains `encoding` and runtime parameters.
 - `TypeEncoderFn` value converter for generic Dart -> Postgres object encoders (where type is not specified as parameter).
+- `RelationTracker` tracks information about relations (currently limited to `RelationMessage` caching).
 - `RuntimeParameters` to access server-provided parameter status values.
 
 ## 3.3.0

lib/src/types/type_codec.dart

@@ -3,6 +3,8 @@ import 'dart:collection';
 import 'dart:convert';
 import 'dart:typed_data';
 
+import 'package:postgres/src/v3/relation_tracker.dart';
+
 import '../buffer.dart';
 import 'type_registry.dart';
 
@@ -85,11 +87,13 @@ class RuntimeParameters {
 
 class TypeCodecContext {
   final Encoding encoding;
+  final RelationTracker relationTracker;
   final RuntimeParameters runtimeParameters;
   final TypeRegistry typeRegistry;
 
   TypeCodecContext({
     required this.encoding,
+    required this.relationTracker,
     required this.runtimeParameters,
     required this.typeRegistry,
   });

lib/src/v3/connection.dart

@@ -12,10 +12,12 @@ import 'package:stream_channel/stream_channel.dart';
 
 import '../../postgres.dart';
 import '../auth/auth.dart';
+import '../messages/logical_replication_messages.dart';
 import '../types/type_codec.dart';
 import '../types/type_registry.dart';
 import 'protocol.dart';
 import 'query_description.dart';
+import 'relation_tracker.dart';
 import 'resolved_settings.dart';
 
 const _debugLog = false;
@@ -348,6 +350,9 @@ class PgConnectionImplementation extends _PgSessionBase implements Connection {
   late final runtimeParameters =
       RuntimeParameters(latestValues: UnmodifiableMapView(_parameters));
 
+  // TODO: share this between pooled connections
+  final _relationTracker = RelationTracker();
+
   var _statementCounter = 0;
   var _portalCounter = 0;
   var _queryCount = 0;
@@ -406,6 +411,13 @@ class PgConnectionImplementation extends _PgSessionBase implements Connection {
     try {
       message as ServerMessage;
 
+      if (message is XLogDataLogicalMessage) {
+        final embedded = message.message;
+        if (embedded is RelationMessage) {
+          _relationTracker.addRelationMessage(embedded);
+        }
+      }
+
       if (message is ParameterStatusMessage) {
         _parameters[message.name] = message.value;
       } else if (message is BackendKeyMessage || message is NoticeMessage) {
@@ -541,6 +553,7 @@ class PgConnectionImplementation extends _PgSessionBase implements Connection {
   TypeCodecContext createTypeCodecContext() {
     return TypeCodecContext(
       encoding: encoding,
+      relationTracker: _relationTracker,
       runtimeParameters: runtimeParameters,
       typeRegistry: _settings.typeRegistry,
     );

lib/src/v3/relation_tracker.dart

@@ -0,0 +1,32 @@
+import 'package:postgres/src/messages/logical_replication_messages.dart';
+
+/// Trackes and caches the type and name info of relations (tables, views, indexes...).
+///
+/// Currently it only collects and caches [RelationMessage] instances.
+///
+/// TODO: Implement active querying using `pg_class` like the below query:
+///       "SELECT relname FROM pg_class WHERE relkind='r' AND oid = ?",
+///       https://www.postgresql.org/docs/current/catalog-pg-class.html
+class RelationTracker {
+  final _relationMessages = <int, RelationMessage>{};
+
+  /// Returns the type OID for [relationId] and [columnIndex].
+  /// Returns `null` if the [relationId] is unknown or the [columnIndex]
+  /// is out of bounds.
+  int? getTypeOid(int relationId, int columnIndex) {
+    final m = _relationMessages[relationId];
+    if (m == null) {
+      return null;
+    }
+    if (columnIndex < 0 || columnIndex > m.columns.length) {
+      return null;
+    }
+    return m.columns[columnIndex].typeOid;
+  }
+}
+
+extension RelationInfoViewExt on RelationTracker {
+  void addRelationMessage(RelationMessage message) {
+    _relationMessages[message.relationId] = message;
+  }
+}