[Kernel] Resolve some TODOs

kernel/kernel-api/src/main/java/io/delta/kernel/Scan.java

@@ -86,7 +86,7 @@ public interface Scan {
      *  </ul></li>
      *  <li><ul>
      *      <li>name: {@code tableRoot}, type: {@code string}</li>
-     *      <li>Description: Absolute path of the table location. TODO: this is temporary. Will
+     *      <li>Description: Absolute path of the table location. NOTE: this is temporary. Will
      *      be removed in future. @see <a href=https://github.com/delta-io/delta/issues/2089>
      *          </a></li>
      *  </ul></li>

kernel/kernel-api/src/main/java/io/delta/kernel/expressions/Literal.java

@@ -49,7 +49,7 @@ public final class Literal implements Expression {
      * @return a {@link Literal} of type {@link BooleanType}
      */
     public static Literal ofBoolean(boolean value) {
-        return new Literal(value, BooleanType.INSTANCE);
+        return new Literal(value, BooleanType.BOOLEAN);
     }
 
     /**
@@ -59,7 +59,7 @@ public static Literal ofBoolean(boolean value) {
      * @return a {@link Literal} of type {@link ByteType}
      */
     public static Literal ofByte(byte value) {
-        return new Literal(value, ByteType.INSTANCE);
+        return new Literal(value, ByteType.BYTE);
     }
 
     /**
@@ -69,7 +69,7 @@ public static Literal ofByte(byte value) {
      * @return a {@link Literal} of type {@link ShortType}
      */
     public static Literal ofShort(short value) {
-        return new Literal(value, ShortType.INSTANCE);
+        return new Literal(value, ShortType.SHORT);
     }
 
     /**
@@ -79,7 +79,7 @@ public static Literal ofShort(short value) {
      * @return a {@link Literal} of type {@link IntegerType}
      */
     public static Literal ofInt(int value) {
-        return new Literal(value, IntegerType.INSTANCE);
+        return new Literal(value, IntegerType.INTEGER);
     }
 
     /**
@@ -89,7 +89,7 @@ public static Literal ofInt(int value) {
      * @return a {@link Literal} of type {@link LongType}
      */
     public static Literal ofLong(long value) {
-        return new Literal(value, LongType.INSTANCE);
+        return new Literal(value, LongType.LONG);
     }
 
     /**
@@ -99,7 +99,7 @@ public static Literal ofLong(long value) {
      * @return a {@link Literal} of type {@link FloatType}
      */
     public static Literal ofFloat(float value) {
-        return new Literal(value, FloatType.INSTANCE);
+        return new Literal(value, FloatType.FLOAT);
     }
 
     /**
@@ -109,7 +109,7 @@ public static Literal ofFloat(float value) {
      * @return a {@link Literal} of type {@link DoubleType}
      */
     public static Literal ofDouble(double value) {
-        return new Literal(value, DoubleType.INSTANCE);
+        return new Literal(value, DoubleType.DOUBLE);
     }
 
     /**
@@ -119,7 +119,7 @@ public static Literal ofDouble(double value) {
      * @return a {@link Literal} of type {@link StringType}
      */
     public static Literal ofString(String value) {
-        return new Literal(value, StringType.INSTANCE);
+        return new Literal(value, StringType.STRING);
     }
 
     /**
@@ -129,7 +129,7 @@ public static Literal ofString(String value) {
      * @return a {@link Literal} of type {@link BinaryType}
      */
     public static Literal ofBinary(byte[] value) {
-        return new Literal(value, BinaryType.INSTANCE);
+        return new Literal(value, BinaryType.BINARY);
     }
 
     /**
@@ -139,7 +139,7 @@ public static Literal ofBinary(byte[] value) {
      * @return a {@link Literal} of type {@link DateType}
      */
     public static Literal ofDate(int daysSinceEpochUTC) {
-        return new Literal(daysSinceEpochUTC, DateType.INSTANCE);
+        return new Literal(daysSinceEpochUTC, DateType.DATE);
     }
 
     /**
@@ -149,7 +149,7 @@ public static Literal ofDate(int daysSinceEpochUTC) {
      * @return a {@link Literal} with data type {@link TimestampType}
      */
     public static Literal ofTimestamp(long microsSinceEpochUTC) {
-        return new Literal(microsSinceEpochUTC, TimestampType.INSTANCE);
+        return new Literal(microsSinceEpochUTC, TimestampType.TIMESTAMP);
     }
 
     /**

kernel/kernel-api/src/main/java/io/delta/kernel/internal/InternalScanFileUtils.java

@@ -43,7 +43,7 @@ public class InternalScanFileUtils {
     private InternalScanFileUtils() {}
 
     private static final String TABLE_ROOT_COL_NAME = "tableRoot";
-    private static final DataType TABLE_ROOT_DATA_TYPE = StringType.INSTANCE;
+    private static final DataType TABLE_ROOT_DATA_TYPE = StringType.STRING;
     /**
      * {@link Column} expression referring to the `partitionValues` in scan `add` file.
      */
@@ -58,7 +58,7 @@ private InternalScanFileUtils() {}
 
     public static final StructType SCAN_FILE_SCHEMA = new StructType()
         .add("add", AddFile.SCHEMA)
-        // TODO: table root is temporary, until the path in `add.path` is converted to
+        // NOTE: table root is temporary, until the path in `add.path` is converted to
         // an absolute path. https://github.com/delta-io/delta/issues/2089
         .add(TABLE_ROOT_COL_NAME, TABLE_ROOT_DATA_TYPE);
 

kernel/kernel-api/src/main/java/io/delta/kernel/internal/actions/AddFile.java

@@ -21,15 +21,15 @@
  * Delta log action representing an `AddFile`
  */
 public class AddFile {
-    // TODO: there are more optional fields in `AddFile` according to the spec. We will be adding
+    // Note: these are more optional fields in `AddFile` according to the spec. We will be adding
     // them in read schema as we support the related features.
     public static final StructType SCHEMA = new StructType()
-        .add("path", StringType.INSTANCE, false /* nullable */)
+        .add("path", StringType.STRING, false /* nullable */)
         .add("partitionValues",
-            new MapType(StringType.INSTANCE, StringType.INSTANCE, true),
+            new MapType(StringType.STRING, StringType.STRING, true),
             false /* nullable*/)
-        .add("size", LongType.INSTANCE, false /* nullable*/)
-        .add("modificationTime", LongType.INSTANCE, false /* nullable*/)
-        .add("dataChange", BooleanType.INSTANCE, false /* nullable*/)
+        .add("size", LongType.LONG, false /* nullable*/)
+        .add("modificationTime", LongType.LONG, false /* nullable*/)
+        .add("dataChange", BooleanType.BOOLEAN, false /* nullable*/)
         .add("deletionVector", DeletionVectorDescriptor.READ_SCHEMA, true /* nullable */);
 }

kernel/kernel-api/src/main/java/io/delta/kernel/internal/actions/DeletionVectorDescriptor.java

@@ -63,11 +63,11 @@ public static DeletionVectorDescriptor fromRow(Row row) {
     public static final String UUID_DV_MARKER = "u";
 
     public static final StructType READ_SCHEMA = new StructType()
-        .add("storageType", StringType.INSTANCE, false /* nullable*/)
-        .add("pathOrInlineDv", StringType.INSTANCE, false /* nullable*/)
-        .add("offset", IntegerType.INSTANCE, true /* nullable*/)
-        .add("sizeInBytes", IntegerType.INSTANCE, false /* nullable*/)
-        .add("cardinality", LongType.INSTANCE, false /* nullable*/);
+        .add("storageType", StringType.STRING, false /* nullable*/)
+        .add("pathOrInlineDv", StringType.STRING, false /* nullable*/)
+        .add("offset", IntegerType.INTEGER, true /* nullable*/)
+        .add("sizeInBytes", IntegerType.INTEGER, false /* nullable*/)
+        .add("cardinality", LongType.LONG, false /* nullable*/);
 
     private static final Map<String, Integer> COL_NAME_TO_ORDINAL =
         IntStream.range(0, READ_SCHEMA.length())

kernel/kernel-api/src/main/java/io/delta/kernel/internal/actions/Format.java

@@ -32,9 +32,9 @@ public static Format fromRow(Row row) {
     }
 
     public static final StructType READ_SCHEMA = new StructType()
-        .add("provider", StringType.INSTANCE, false /* nullable */)
+        .add("provider", StringType.STRING, false /* nullable */)
         .add("options",
-            new MapType(StringType.INSTANCE, StringType.INSTANCE, false),
+            new MapType(StringType.STRING, StringType.STRING, false),
             true /* nullable */
         );
 

kernel/kernel-api/src/main/java/io/delta/kernel/internal/actions/Metadata.java

@@ -58,17 +58,17 @@ public static Metadata fromRow(Row row, TableClient tableClient) {
     }
 
     public static final StructType READ_SCHEMA = new StructType()
-        .add("id", StringType.INSTANCE, false /* nullable */)
-        .add("name", StringType.INSTANCE, true /* nullable */)
-        .add("description", StringType.INSTANCE, true /* nullable */)
+        .add("id", StringType.STRING, false /* nullable */)
+        .add("name", StringType.STRING, true /* nullable */)
+        .add("description", StringType.STRING, true /* nullable */)
         .add("format", Format.READ_SCHEMA, false /* nullable */)
-        .add("schemaString", StringType.INSTANCE, false /* nullable */)
+        .add("schemaString", StringType.STRING, false /* nullable */)
         .add("partitionColumns",
-            new ArrayType(StringType.INSTANCE, false /* contains null */),
+            new ArrayType(StringType.STRING, false /* contains null */),
             false /* nullable */)
-        .add("createdTime", LongType.INSTANCE, true /* contains null */)
+        .add("createdTime", LongType.LONG, true /* contains null */)
         .add("configuration",
-            new MapType(StringType.INSTANCE, StringType.INSTANCE, false),
+            new MapType(StringType.STRING, StringType.STRING, false),
             false /* nullable */);
 
     private final String id;

kernel/kernel-api/src/main/java/io/delta/kernel/internal/actions/Protocol.java

@@ -40,10 +40,10 @@ public static Protocol fromRow(Row row) {
     }
 
     public static final StructType READ_SCHEMA = new StructType()
-        .add("minReaderVersion", IntegerType.INSTANCE, false /* nullable */)
-        .add("minWriterVersion", IntegerType.INSTANCE, false /* nullable */)
-        .add("readerFeatures", new ArrayType(StringType.INSTANCE, false /* contains null */))
-        .add("writerFeatures", new ArrayType(StringType.INSTANCE, false /* contains null */));
+        .add("minReaderVersion", IntegerType.INTEGER, false /* nullable */)
+        .add("minWriterVersion", IntegerType.INTEGER, false /* nullable */)
+        .add("readerFeatures", new ArrayType(StringType.STRING, false /* contains null */))
+        .add("writerFeatures", new ArrayType(StringType.STRING, false /* contains null */));
 
     private final int minReaderVersion;
     private final int minWriterVersion;

kernel/kernel-api/src/main/java/io/delta/kernel/internal/checkpoints/CheckpointMetaData.java

@@ -30,11 +30,10 @@ public static CheckpointMetaData fromRow(Row row) {
         );
     }
 
-    // TODO: there are more optional fields
     public static StructType READ_SCHEMA = new StructType()
-        .add("version", LongType.INSTANCE, false /* nullable */)
-        .add("size", LongType.INSTANCE, false /* nullable */)
-        .add("parts", LongType.INSTANCE);
+        .add("version", LongType.LONG, false /* nullable */)
+        .add("size", LongType.LONG, false /* nullable */)
+        .add("parts", LongType.LONG);
 
     public final long version;
     public final long size;

kernel/kernel-api/src/main/java/io/delta/kernel/internal/checkpoints/Checkpointer.java

@@ -98,9 +98,8 @@ public Optional<CheckpointMetaData> readLastCheckpointFile(TableClient tableClie
      */
     private Optional<CheckpointMetaData> loadMetadataFromFile(TableClient tableClient) {
         try {
-            // TODO: we have no way to get the file size and modification time within the api
-            // module. Should we have a client API for that or make use of the
-            // `FileSystemClient#listFrom`?
+            // For now we use file size = 0 and modification time = 0, in the future we should use
+            // listFrom to retrieve the real values see delta-io/delta#2140
             FileStatus lastCheckpointFile = FileStatus.of(lastCheckpointFilePath.toString(), 0, 0);
             JsonHandler jsonHandler = tableClient.getJsonHandler();
             try (CloseableIterator<FileReadContext> fileReadContextIter =

kernel/kernel-api/src/main/java/io/delta/kernel/internal/data/ScanStateRow.java

@@ -36,13 +36,13 @@
  */
 public class ScanStateRow extends GenericRow {
     private static final StructType SCHEMA = new StructType()
-        .add("configuration", new MapType(StringType.INSTANCE, StringType.INSTANCE, false))
-        .add("logicalSchemaString", StringType.INSTANCE)
-        .add("physicalSchemaString", StringType.INSTANCE)
-        .add("partitionColumns", new ArrayType(StringType.INSTANCE, false))
-        .add("minReaderVersion", IntegerType.INSTANCE)
-        .add("minWriterVersion", IntegerType.INSTANCE)
-        .add("tablePath", StringType.INSTANCE);
+        .add("configuration", new MapType(StringType.STRING, StringType.STRING, false))
+        .add("logicalSchemaString", StringType.STRING)
+        .add("physicalSchemaString", StringType.STRING)
+        .add("partitionColumns", new ArrayType(StringType.STRING, false))
+        .add("minReaderVersion", IntegerType.INTEGER)
+        .add("minWriterVersion", IntegerType.INTEGER)
+        .add("tablePath", StringType.STRING);
 
     private static final Map<String, Integer> COL_NAME_TO_ORDINAL =
         IntStream.range(0, SCHEMA.length())

kernel/kernel-api/src/main/java/io/delta/kernel/internal/data/SelectionColumnVector.java

@@ -38,7 +38,7 @@ public SelectionColumnVector(RoaringBitmapArray bitmap, ColumnVector rowIndices)
 
     @Override
     public DataType getDataType() {
-        return BooleanType.INSTANCE;
+        return BooleanType.BOOLEAN;
     }
 
     @Override

kernel/kernel-api/src/main/java/io/delta/kernel/internal/deletionvectors/RoaringBitmapArray.java

@@ -27,9 +27,6 @@
 
 import static io.delta.kernel.internal.util.InternalUtils.checkArgument;
 
-// TODO: add test suite
-// If we implement additional methods (i.e. serialize) we can copy the test suite from delta-spark
-
 /**
  * A 64-bit extension of [[RoaringBitmap]] that is optimized for cases that usually fit within
  * a 32-bit bitmap, but may run over by a few bits on occasion.

kernel/kernel-api/src/main/java/io/delta/kernel/internal/fs/Path.java

@@ -29,8 +29,8 @@
  * <p>
  * Taken from https://github.com/apache/hadoop/blob/branch-3.3
  * .4/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/Path.java
- * TODO: remove unused parts
  */
+// TODO remove this class
 public class Path
     implements Comparable<Path>, Serializable, ObjectInputValidation {
 

kernel/kernel-api/src/main/java/io/delta/kernel/internal/replay/ActiveAddFilesIterator.java

@@ -220,7 +220,7 @@ private void prepareNext() {
                 .getEvaluator(
                     scanAddFiles.getSchema(),
                     Literal.ofString(tableRoot.toUri().toString()),
-                    StringType.INSTANCE);
+                    StringType.STRING);
         }
         ColumnVector tableRootVector = tableRootVectorGenerator.eval(scanAddFiles);
         scanAddFiles = scanAddFiles.withNewColumn(

kernel/kernel-api/src/main/java/io/delta/kernel/internal/replay/LogReplay.java

@@ -66,7 +66,7 @@ public class LogReplay implements Logging {
         // the whether stats are needed or not: https://github.com/delta-io/delta/issues/1961
         .add("add", AddFile.SCHEMA)
         .add("remove", new StructType()
-            .add("path", StringType.INSTANCE, false /* nullable */)
+            .add("path", StringType.STRING, false /* nullable */)
             .add("deletionVector", DeletionVectorDescriptor.READ_SCHEMA, true /* nullable */)
         );
 

kernel/kernel-api/src/main/java/io/delta/kernel/types/MixedDataType.java → kernel/kernel-api/src/main/java/io/delta/kernel/internal/types/MixedDataType.java

@@ -13,13 +13,15 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package io.delta.kernel.types;
+package io.delta.kernel.internal.types;
 
 import io.delta.kernel.annotation.Evolving;
 import io.delta.kernel.data.ColumnVector;
+import io.delta.kernel.types.DataType;
+import io.delta.kernel.types.StructType;
 
 /**
- * TODO:
+ * TODO: this is temporary
  * This is a controversial data type to have, but we have no way to specify the schema
  * of JSON serialized table schema. In order to use the
  * {@link io.delta.kernel.client.JsonHandler#parseJson(ColumnVector, StructType)}, the Kernel

kernel/kernel-api/src/main/java/io/delta/kernel/internal/types/TableSchemaSerDe.java

@@ -34,13 +34,13 @@
 import io.delta.kernel.types.DataType;
 import io.delta.kernel.types.DecimalType;
 import io.delta.kernel.types.MapType;
-import io.delta.kernel.types.MixedDataType;
 import io.delta.kernel.types.StringType;
 import io.delta.kernel.types.StructField;
 import io.delta.kernel.types.StructType;
 import io.delta.kernel.utils.CloseableIterator;
 import io.delta.kernel.utils.Utils;
 import io.delta.kernel.utils.VectorUtils;
+import io.delta.kernel.internal.util.InternalUtils;
 
 /**
  * Utility class to serialize and deserialize the table schema which is of type {@link StructType}.
@@ -190,7 +190,7 @@ private static <R> R parseAndEvalSingleRow(
         String jsonString,
         StructType outputSchema,
         Function<Row, R> evalFunction) {
-        ColumnVector columnVector = Utils.singletonColumnVector(jsonString);
+        ColumnVector columnVector = InternalUtils.singletonStringColumnVector(jsonString);
         ColumnarBatch result = jsonHandler.parseJson(columnVector, outputSchema);
 
         assert result.getSize() == 1;
@@ -207,11 +207,11 @@ private static <R> R parseAndEvalSingleRow(
      * Schema of the one member ({@link StructField}) in {@link StructType}.
      */
     private static final StructType STRUCT_FIELD_SCHEMA = new StructType()
-        .add("name", StringType.INSTANCE)
+        .add("name", StringType.STRING)
         .add("type", MixedDataType.INSTANCE) // Data type can be a string or a object.
-        .add("nullable", BooleanType.INSTANCE)
+        .add("nullable", BooleanType.BOOLEAN)
         .add("metadata",
-            new MapType(StringType.INSTANCE, StringType.INSTANCE, false /* valueContainsNull */));
+            new MapType(StringType.STRING, StringType.STRING, false /* valueContainsNull */));
 
     /**
      * Schema of the serialized {@link StructType}.
@@ -238,9 +238,9 @@ private static <R> R parseAndEvalSingleRow(
      */
     private static StructType ARRAY_TYPE_SCHEMA =
         new StructType()
-            .add("type", StringType.INSTANCE)
+            .add("type", StringType.STRING)
             .add("elementType", MixedDataType.INSTANCE)
-            .add("containsNull", BooleanType.INSTANCE);
+            .add("containsNull", BooleanType.BOOLEAN);
 
     /**
      * Example Map Type in serialized format
@@ -253,10 +253,10 @@ private static <R> R parseAndEvalSingleRow(
      */
     private static StructType MAP_TYPE_SCHEMA =
         new StructType()
-            .add("type", StringType.INSTANCE)
+            .add("type", StringType.STRING)
             .add("keyType", MixedDataType.INSTANCE)
             .add("valueType", MixedDataType.INSTANCE)
-            .add("valueContainsNull", BooleanType.INSTANCE);
+            .add("valueContainsNull", BooleanType.BOOLEAN);
 
     private static Pattern DECIMAL_TYPE_PATTERN =
         Pattern.compile("decimal\\(\\s*(?<precision>[0-9]+),\\s*(?<scale>[0-9]+)\\s*\\)");