WIP: Proposed API to determine freshness of a cached table

presto-plugin-toolkit/src/main/java/io/prestosql/plugin/base/classloader/ClassLoaderSafeConnectorMetadata.java

@@ -40,6 +40,7 @@
 import io.prestosql.spi.connector.SchemaTableName;
 import io.prestosql.spi.connector.SchemaTablePrefix;
 import io.prestosql.spi.connector.SystemTable;
+import io.prestosql.spi.connector.TableToken;
 import io.prestosql.spi.expression.ConnectorExpression;
 import io.prestosql.spi.predicate.TupleDomain;
 import io.prestosql.spi.security.GrantInfo;
@@ -677,4 +678,20 @@ public void validateScan(ConnectorSession session, ConnectorTableHandle handle)
             delegate.validateScan(session, handle);
         }
     }
+
+    @Override
+    public Optional<TableToken> getTableToken(ConnectorSession session, ConnectorTableHandle tableHandle, TupleDomain<ColumnHandle> predicate)
+    {
+        try (ThreadContextClassLoader ignored = new ThreadContextClassLoader(classLoader)) {
+            return delegate.getTableToken(session, tableHandle, predicate);
+        }
+    }
+
+    @Override
+    public boolean isTableCurrent(ConnectorSession session, ConnectorTableHandle tableHandle, Optional<TableToken> tableToken, TupleDomain<ColumnHandle> predicate)
+    {
+        try (ThreadContextClassLoader ignored = new ThreadContextClassLoader(classLoader)) {
+            return delegate.isTableCurrent(session, tableHandle, tableToken, predicate);
+        }
+    }
 }

presto-spi/src/main/java/io/prestosql/spi/connector/ConnectorMetadata.java

@@ -823,4 +823,27 @@ default Optional<ConnectorTableHandle> applySample(ConnectorSession session, Con
      * <p>
      */
     default void validateScan(ConnectorSession session, ConnectorTableHandle handle) {}
+
+    /**
+     * API to determine if a table state (data in the table) has changed compared to cached table state in Presto.
+     * The cached table in Presto may take the form of result cache or a materialized view.
+     */
+    /**
+     * Method to request the connector for a token that captures the state of the table given the filters.
+     * Engine does not interpret the token in any way. It simply presents it back to the connector to determine freshness of the cached table
+     * the token is associated with.
+     */
+    default Optional<TableToken> getTableToken(ConnectorSession session, ConnectorTableHandle tableHandle, TupleDomain<ColumnHandle> predicate)
+    {
+        return Optional.empty();
+    }
+
+    /**
+     * Method for the engine to present a table token and applied predicates to request the connector to evaluate if the cached table
+     * is fresh compared to the actual table state.
+     */
+    default boolean isTableCurrent(ConnectorSession session, ConnectorTableHandle tableHandle, Optional<TableToken> tableToken, TupleDomain<ColumnHandle> predicate)
+    {
+        return false;
+    }
 }

presto-spi/src/main/java/io/prestosql/spi/connector/TableToken.java

@@ -0,0 +1,18 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.prestosql.spi.connector;
+
+public interface TableToken
+{
+}