Use BlockingQueue of FrameEnvelopes rather than IO pipes

core/src/main/java/org/apache/calcite/avatica/AvaticaConnection.java

@@ -698,7 +698,7 @@ protected ResultSet createResultSet(Meta.MetaResultSet metaResultSet, QueryState
   }
 
   /** Creates a statement wrapper around an existing handle. */
-  public AvaticaStatement lookupStatement(Meta.StatementHandle h)
+  protected AvaticaStatement lookupStatement(Meta.StatementHandle h)
       throws SQLException {
     final AvaticaStatement statement = statementMap.get(h.id);
     if (statement != null) {
@@ -796,7 +796,7 @@ public <T> T invokeWithRetries(CallableWithoutException<T> callable) {
       } catch (AvaticaClientRuntimeException e) {
         lastException = e;
         if (ErrorResponse.MISSING_CONNECTION_ERROR_CODE == e.getErrorCode()
-            && transparentReconnectEnabled) {
+                && transparentReconnectEnabled) {
           this.openConnection();
           continue;
         }

core/src/main/java/org/apache/calcite/avatica/MetaImpl.java

@@ -1527,12 +1527,12 @@ public Object next() {
 
   /** Iterable that yields an iterator over rows coming from a sequence of
    * {@link Meta.Frame}s. */
-  public class FetchIterable implements Iterable<Object> {
+  private class FetchIterable implements Iterable<Object> {
     private final AvaticaStatement stmt;
     private final QueryState state;
     private final Frame firstFrame;
 
-    public FetchIterable(AvaticaStatement stmt, QueryState state, Frame firstFrame) {
+    private FetchIterable(AvaticaStatement stmt, QueryState state, Frame firstFrame) {
       this.stmt = stmt;
       this.state = state;
       this.firstFrame = firstFrame;
@@ -1544,15 +1544,15 @@ public Iterator<Object> iterator() {
   }
 
   /** Iterator over rows coming from a sequence of {@link Meta.Frame}s. */
-  public class FetchIterator implements Iterator<Object> {
+  private class FetchIterator implements Iterator<Object> {
     private final AvaticaStatement stmt;
     private final QueryState state;
     private final int fetchSize;
     private Frame frame;
     private Iterator<Object> rows;
     private long currentOffset = 0;
 
-    public FetchIterator(AvaticaStatement stmt, QueryState state, Frame firstFrame) {
+    private FetchIterator(AvaticaStatement stmt, QueryState state, Frame firstFrame) {
       this.stmt = stmt;
       this.state = state;
       int fetchRowCount;
@@ -1590,14 +1590,7 @@ public Object next() {
       return o;
     }
 
-    /** A helper method to call {@link Meta#fetch}. Pulled out from {@link #moveNext()} so that
-     * extending classes can override the fetch implementation without calling out to a Meta. */
-    protected Frame doFetch(StatementHandle h, long currentOffset, int fetchSize)
-        throws NoSuchStatementException, MissingResultsException {
-      return fetch(h, currentOffset, fetchSize);
-    }
-
-    void moveNext() {
+    private void moveNext() {
       for (;;) {
         if (rows.hasNext()) {
           break;
@@ -1608,7 +1601,7 @@ void moveNext() {
         }
         try {
           // currentOffset updated after element is read from `rows` iterator
-          frame = doFetch(stmt.handle, currentOffset, fetchSize);
+          frame = fetch(stmt.handle, currentOffset, fetchSize);
         } catch (NoSuchStatementException e) {
           resetStatement();
           // re-fetch the batch where we left off

core/src/main/java/org/apache/calcite/avatica/remote/RemoteMeta.java

@@ -40,11 +40,11 @@
  * driver.
  */
 public class RemoteMeta extends MetaImpl {
-  public final Service service;
+  final Service service;
   final Map<String, ConnectionPropertiesImpl> propsMap = new HashMap<>();
   private Map<DatabaseProperty, Object> databaseProperties;
 
-  public RemoteMeta(AvaticaConnection connection, Service service) {
+  protected RemoteMeta(AvaticaConnection connection, Service service) {
     super(connection);
     this.service = service;
   }

core/src/main/java/org/apache/calcite/avatica/remote/Service.java

@@ -38,7 +38,6 @@
 import com.google.protobuf.Message;
 import com.google.protobuf.UnsafeByteOperations;
 
-import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.sql.SQLException;
@@ -147,7 +146,7 @@ protected static int p(int result, long v) {
           name = "prepareAndExecuteBatch"),
       @JsonSubTypes.Type(value = ExecuteBatchRequest.class, name = "executeBatch") })
   abstract class Request extends Base {
-    abstract Response accept(Service service) throws IOException;
+    abstract Response accept(Service service);
     abstract Request deserialize(Message genericMsg);
     abstract Message serialize();
   }
@@ -949,7 +948,7 @@ public PrepareAndExecuteRequest(
       this.maxRowsInFirstFrame = maxRowsInFirstFrame;
     }
 
-    @Override ExecuteResponse accept(Service service) throws IOException {
+    @Override ExecuteResponse accept(Service service) {
       return service.apply(this);
     }
 

core/src/main/java/org/apache/calcite/avatica/remote/looker/Driver.java

@@ -21,14 +21,20 @@
 import org.apache.calcite.avatica.Meta;
 import org.apache.calcite.avatica.UnregisteredDriver;
 import org.apache.calcite.avatica.remote.Service;
-import org.apache.calcite.avatica.remote.looker.utils.LookerSdkFactory;
 
 import com.looker.sdk.LookerSDK;
 
 import java.sql.Connection;
 import java.sql.SQLException;
 import java.util.Properties;
 
+/**
+ * JDBC Driver for Looker's SQL Interface. Communicates with a Looker instance via
+ * {@link LookerSDK}. Backed by Looker-specific {@link LookerRemoteMeta} and
+ * {@link LookerRemoteService}.
+ *
+ * Use 'jdbc:looker' as the protocol to select this over the default remote Avatica driver.
+ */
 public class Driver extends UnregisteredDriver {
 
   static {
@@ -69,12 +75,14 @@ public Meta createMeta(AvaticaConnection connection) {
     AvaticaConnection conn = (AvaticaConnection) super.connect(url, info);
 
     if (conn == null) {
-      // It's not an url for our driver
+      // the URL did not match Looker's JDBC connection string prefix
       return null;
     }
-    Service service = conn.getService();
+
     // the `looker` driver should always have a matching Service
+    Service service = conn.getService();
     assert service instanceof LookerRemoteService;
+
     // create and set LookerSDK for the connection
     LookerSDK sdk = LookerSdkFactory.createSdk(conn.config().url(), info);
     ((LookerRemoteService) service).setSdk(sdk);