[Kernel] Clean up package organization of kernel-default module.

kernel/README.md

@@ -26,7 +26,7 @@ Notice that there two sets of public APIs to build connectors.
 # Project setup with Delta Kernel 
 The Delta Kernel project provides the following two Maven artifacts:
 - `delta-kernel-api`: This is a must-have dependency and contains all the public `Table` and `TableClient` APIs discussed earlier.
-- `delta-kernel-default`: This is an optional dependency that contains *default* implementations of the `TableClient` interfaces using Hadoop libraries. Developers can optionally use these default implementations to speed up the development of their Delta connector.
+- `delta-kernel-defaults`: This is an optional dependency that contains *default* implementations of the `TableClient` interfaces using Hadoop libraries. Developers can optionally use these default implementations to speed up the development of their Delta connector.
 ```xml
 <!-- Must have dependency -->
 <dependency>
@@ -38,7 +38,7 @@ The Delta Kernel project provides the following two Maven artifacts:
 <!-- Optional dependency -->
 <dependency>
   <groupId>io.delta</groupId>
-  <artifactId>delta-kernel-default</artifactId>
+  <artifactId>delta-kernel-defaults</artifactId>
   <version>VERSION</version>
 </dependency>
 ```

kernel/build.sbt

@@ -76,10 +76,10 @@ val scalaTestVersion = "3.2.15"
 val deltaSparkVersion = deltaStorageVersion
 val sparkVersion = "3.3.2"
 
-lazy val kernelDefault = (project in file("kernel-default"))
+lazy val kernelDefaults = (project in file("kernel-defaults"))
   .dependsOn(kernelApi)
   .settings(
-    name := "delta-kernel-default",
+    name := "delta-kernel-defaults",
     commonSettings,
     scalaStyleSettings,
     releaseSettings,

kernel/dev/checkstyle.xml

@@ -197,11 +197,15 @@
         <blank line>
         import io.delta.kernel.*
         import io.delta.kernel.internal.*
+        <blank line>
+        import io.delta.kernel.defaults.*
+        import io.delta.kernel.defaults.internal.*
         -->
         <module name="ImportOrder">
             <property name="separated" value="true"/>
             <property name="ordered" value="true"/>
-            <property name="groups" value="java,javax,scala,*,io.delta.kernel,io.delta.kernel.internal"/>
+            <property name="groups"
+                      value="java,javax,scala,*,io.delta.kernel,io.delta.kernel.internal,io.delta.kernel.defaults,io.delta.kernel.defaults.internal"/>
             <property name="option" value="under"/>
         </module>
 
@@ -216,6 +220,13 @@
             <property name="checks" value="ImportOrder"/>
             <property name="message" value="^'io.delta.kernel.internal\..*'.*"/>
         </module>
+
+        <!-- io.delta.kernel.defaults and io.delta.kernel.defaults.internal -->
+        <module name="SuppressionXpathSingleFilter">
+            <property name="checks" value="ImportOrder"/>
+            <property name="message" value="^'io.delta.kernel.defaults.internal\..*'.*"/>
+        </module>
+
         <!-- java and javax -->
         <module name="SuppressionXpathSingleFilter">
             <property name="checks" value="ImportOrder"/>

kernel/examples/table-reader/pom.xml

@@ -47,7 +47,7 @@ limitations under the License.-->
 
         <dependency>
             <groupId>io.delta</groupId>
-            <artifactId>delta-kernel-default</artifactId>
+            <artifactId>delta-kernel-defaults</artifactId>
             <version>${delta-kernel.version}</version>
         </dependency>
 

kernel/examples/table-reader/src/main/java/io/delta/kernel/examples/BaseTableReader.java

@@ -21,6 +21,9 @@
 import java.util.Optional;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
+import static java.lang.String.format;
+import static java.util.Objects.requireNonNull;
+
 import org.apache.commons.cli.CommandLine;
 import org.apache.commons.cli.CommandLineParser;
 import org.apache.commons.cli.DefaultParser;
@@ -31,38 +34,34 @@
 import org.apache.hadoop.conf.Configuration;
 
 import io.delta.kernel.TableNotFoundException;
-import io.delta.kernel.client.DefaultTableClient;
 import io.delta.kernel.client.TableClient;
 import io.delta.kernel.data.ColumnVector;
 import io.delta.kernel.data.ColumnarBatch;
 import io.delta.kernel.data.DataReadResult;
-import io.delta.kernel.data.vector.VectorUtils;
 import io.delta.kernel.types.StructField;
 import io.delta.kernel.types.StructType;
 
-import static java.lang.String.format;
-import static java.util.Objects.requireNonNull;
+import io.delta.kernel.defaults.client.DefaultTableClient;
+import io.delta.kernel.defaults.internal.data.vector.VectorUtils;
 
 /**
  * Base class for reading Delta Lake tables using the Delta Kernel APIs.
  */
-public abstract class BaseTableReader
-{
+public abstract class BaseTableReader {
     public static final int DEFAULT_LIMIT = 20;
 
     protected final String tablePath;
     protected final TableClient tableClient;
 
-    public BaseTableReader(String tablePath)
-    {
+    public BaseTableReader(String tablePath) {
         this.tablePath = requireNonNull(tablePath);
         this.tableClient = DefaultTableClient.create(new Configuration());
     }
 
     /**
      * Show the given {@code limit} rows containing the given columns from the table.
      *
-     * @param limit Max number of rows to show.
+     * @param limit      Max number of rows to show.
      * @param columnsOpt If null, show all columns in the table.
      * @throws TableNotFoundException
      * @throws IOException
@@ -74,8 +73,7 @@ public abstract void show(int limit, Optional<List<String>> columnsOpt)
      * Utility method to return a pruned schema that contains the given {@code columns} from
      * {@code baseSchema}
      */
-    protected static StructType pruneSchema(StructType baseSchema, Optional<List<String>> columns)
-    {
+    protected static StructType pruneSchema(StructType baseSchema, Optional<List<String>> columns) {
         if (!columns.isPresent()) {
             return baseSchema;
         }
@@ -90,8 +88,7 @@ protected static StructType pruneSchema(StructType baseSchema, Optional<List<Str
         return new StructType(selectedFields);
     }
 
-    protected static int printData(DataReadResult dataReadResult, int maxRowsToPrint)
-    {
+    protected static int printData(DataReadResult dataReadResult, int maxRowsToPrint) {
         int printedRowCount = 0;
         ColumnarBatch data = dataReadResult.getData();
         Optional<ColumnVector> selectionVector = dataReadResult.getSelectionVector();
@@ -107,13 +104,11 @@ protected static int printData(DataReadResult dataReadResult, int maxRowsToPrint
         return printedRowCount;
     }
 
-    protected static void printSchema(StructType schema)
-    {
+    protected static void printSchema(StructType schema) {
         System.out.printf(formatter(schema.length()), schema.fieldNames().toArray(new String[0]));
     }
 
-    protected static void printRow(ColumnarBatch batch, int rowId)
-    {
+    protected static void printRow(ColumnarBatch batch, int rowId) {
         int numCols = batch.getSchema().length();
         Object[] rowValues = IntStream.range(0, numCols).mapToObj(colOrdinal -> {
             ColumnVector columnVector = batch.getColumnVector(colOrdinal);
@@ -126,18 +121,10 @@ protected static void printRow(ColumnarBatch batch, int rowId)
         System.out.printf(formatter(numCols), rowValues);
     }
 
-    private static String formatter(int length)
-    {
-        return IntStream.range(0, length)
-            .mapToObj(i -> "%20s")
-            .collect(Collectors.joining("|")) + "\n";
-    }
-
     /**
      * Minimum command line options for any implementation of this reader.
      */
-    protected static Options baseOptions()
-    {
+    protected static Options baseOptions() {
         return new Options()
             .addRequiredOption("t", "table", true, "Fully qualified table path")
             .addOption("c", "columns", true,
@@ -157,14 +144,12 @@ protected static Options baseOptions()
     /**
      * Helper method to parse the command line arguments.
      */
-    protected static CommandLine parseArgs(Options options, String[] args)
-    {
+    protected static CommandLine parseArgs(Options options, String[] args) {
         CommandLineParser cliParser = new DefaultParser();
 
         try {
             return cliParser.parse(options, args);
-        }
-        catch (ParseException parseException) {
+        } catch (ParseException parseException) {
             new HelpFormatter().printHelp(
                 "java " + SingleThreadedTableReader.class.getCanonicalName(),
                 options,
@@ -175,19 +160,23 @@ protected static CommandLine parseArgs(Options options, String[] args)
         return null;
     }
 
-    protected static Optional<List<String>> parseColumnList(CommandLine cli, String optionName)
-    {
+    protected static Optional<List<String>> parseColumnList(CommandLine cli, String optionName) {
         return Optional.ofNullable(cli.getOptionValue(optionName))
             .map(colString -> Arrays.asList(colString.split(",[ ]*")));
     }
 
     protected static int parseInt(CommandLine cli, String optionName, int defaultValue)
-        throws ParseException
-    {
+        throws ParseException {
         return Optional.ofNullable(cli.getParsedOptionValue(optionName))
             .map(Number.class::cast)
             .map(Number::intValue)
             .orElse(defaultValue);
     }
+
+    private static String formatter(int length) {
+        return IntStream.range(0, length)
+            .mapToObj(i -> "%20s")
+            .collect(Collectors.joining("|")) + "\n";
+    }
 }