Added a basic JsonRow

Author: scottsand-db

core/src/main/java/io/delta/core/data/Row.java

@@ -8,35 +8,35 @@
 
 public interface Row {
 
-    boolean isNullAt(int ordinal);
-
-    boolean getBoolean(int ordinal);
-
-    byte getByte(int ordinal);
-
-    short getShort(int ordinal);
-
-    int getInt(int ordinal);
+//    boolean isNullAt(int ordinal);
+//
+//    boolean getBoolean(int ordinal);
+//
+//    byte getByte(int ordinal);
+//
+//    short getShort(int ordinal);
+//
+//    int getInt(int ordinal);
 
     long getLong(int ordinal);
 
-    float getFloat(int ordinal);
-
-    double getDouble(int ordinal);
-
-    BigDecimal getDecimal(int ordinal, int precision, int scale);
-
-    String getString(int ordinal);
-
-    byte[] getBinary(int ordinal);
-
-    Timestamp getTimestamp(int ordinal);
-
-    Date getDate(int ordinal);
-
-    Row getRecord(int ordinal);
-
-    <T> List<T> getList(int ordinal);
-
-    <K, V> Map<K, V> getMap(int ordinal);
+//    float getFloat(int ordinal);
+//
+//    double getDouble(int ordinal);
+//
+//    BigDecimal getDecimal(int ordinal, int precision, int scale);
+//
+//    String getString(int ordinal);
+//
+//    byte[] getBinary(int ordinal);
+//
+//    Timestamp getTimestamp(int ordinal);
+//
+//    Date getDate(int ordinal);
+//
+//    Row getRecord(int ordinal);
+//
+//    <T> List<T> getList(int ordinal);
+//
+//    <K, V> Map<K, V> getMap(int ordinal);
 }

core/src/main/java/io/delta/core/helpers/TableHelper.java

@@ -12,15 +12,7 @@ public interface TableHelper {
 
     CloseableIterator<FileStatus> listFiles(String path) throws FileNotFoundException;
 
-    CloseableIterator<FileStatus> listFiles(String path, String prefixToListFrom) throws FileNotFoundException;
-
-    // DECISION 1 OPTION 1
     CloseableIterator<Row> readJsonFile(String path, StructType readSchema);
-    // each class needs a fromRow()
-
-    // DECISION 1 OPTION 2
-    CloseableIterator<String> readJsonFile(String path);
-    <T> T fromJson(String json, TypeReference<T> typeReference);
 
     /** Uses the readSchema for partition pruning. */
     CloseableIterator<Row> readParquetFile(String path, StructType readSchema);

core/src/main/java/io/delta/core/helpers/TypeReference.java

@@ -1,20 +1,18 @@
 package io.delta.core.internal.checkpoint;
 
 import io.delta.core.data.Row;
-import io.delta.core.helpers.TypeReference;
+import io.delta.core.types.LongType;
 import io.delta.core.types.StructType;
 
 public class CheckpointMetaData {
 
-    // DECISION 1 OPTION 1
     public static CheckpointMetaData fromRow(Row row) {
         return null;
     }
-    // DECISION 1 OPTION 2
-    public static TypeReference<CheckpointMetaData> TYPE_REFERENCE =
-        new TypeReference<CheckpointMetaData>() { };
 
-    public static StructType READ_SCHEMA = null;
+    public static StructType READ_SCHEMA = new StructType()
+        .add("version", new LongType())
+        .add("size", new LongType());
 
     public final long version;
     public final long size;

core/src/main/java/io/delta/core/internal/checkpoint/CheckpointMetaData.java

@@ -72,17 +72,10 @@ public Optional<CheckpointMetaData> readLastCheckpointFile() {
 
     /** Loads the checkpoint metadata from the _last_checkpoint file. */
     private Optional<CheckpointMetaData> loadMetadataFromFile(int tries) {
-        // DECISION 1 OPTION 1
-        final CloseableIterator<Row> data1 =
-            tableImpl.tableHelper.readJsonFile(LAST_CHECKPOINT, CheckpointMetaData.READ_SCHEMA);
-        final Optional<CheckpointMetaData> result1 = Optional.of(CheckpointMetaData.fromRow(data1.next()));
-
-        // DECISION 1 OPTION 2
-        final CloseableIterator<String> data2 = tableImpl.tableHelper.readJsonFile(LAST_CHECKPOINT);
-        final Optional<CheckpointMetaData> result2 = Optional.of(
-            tableImpl.tableHelper.fromJson(data2.next(), CheckpointMetaData.TYPE_REFERENCE)
-        );
-
-        return result1;
+        final CloseableIterator<Row> data1 = tableImpl
+            .tableHelper
+            .readJsonFile(LAST_CHECKPOINT, CheckpointMetaData.READ_SCHEMA);
+
+        return Optional.of(CheckpointMetaData.fromRow(data1.next()));
     }
 }

core/src/main/java/io/delta/core/internal/checkpoint/Checkpointer.java

@@ -96,7 +96,6 @@ private Optional<CloseableIterator<FileStatus>> listFromOrNone(long startVersion
         // LIST the directory, starting from the provided lower bound (treat missing dir as empty).
         // NOTE: "empty/missing" is _NOT_ equivalent to "contains no useful commit files."
         try {
-            // TODO: would be great to build our own better Optional class, e.g. Option.filterNot
             CloseableIterator<FileStatus> results = listFrom(startVersion);
             if (results.hasNext()) {
                 return Optional.of(results);

core/src/main/java/io/delta/core/internal/snapshot/SnapshotManager.java

@@ -1,4 +1,14 @@
 package io.delta.core.types;
 
-public abstract class DataType { }
+import java.util.Locale;
+
+public abstract class DataType {
+    public String typeName() {
+       String name = this.getClass().getSimpleName();
+       if (name.endsWith("Type")) {
+           name = name.substring(0, name.length() - 4);
+       }
+       return name.toLowerCase(Locale.ROOT);
+    }
+}
 

core/src/main/java/io/delta/core/types/DataType.java

@@ -0,0 +1,4 @@
+package io.delta.core.types;
+
+public class LongType extends DataType {
+}

core/src/main/java/io/delta/core/types/LongType.java

@@ -0,0 +1,14 @@
+package io.delta.core.types;
+
+public class StructField {
+    public final String name;
+    public final DataType dataType;
+    public final boolean nullable;
+    // private final FieldMetadata metadata;
+
+    public StructField(String name, DataType dataType, boolean nullable) {
+        this.name = name;
+        this.dataType = dataType;
+        this.nullable = nullable;
+    }
+}

core/src/main/java/io/delta/core/types/StructField.java

@@ -1,3 +1,44 @@
 package io.delta.core.types;
 
-public final class StructType extends DataType { }
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public final class StructType extends DataType {
+    private final List<StructField> fields;
+
+    public StructType() {
+        this(new ArrayList<>());
+    }
+
+    public StructType(List<StructField> fields) {
+        this.fields = fields;
+    }
+
+    public StructType add(StructField field) {
+        final List<StructField> fieldsCopy = new ArrayList<>(fields);
+        fieldsCopy.add(field);
+
+        return new StructType(fieldsCopy);
+    }
+
+    public StructType add(String name, DataType dataType) {
+        return add(new StructField(name, dataType, true /* nullable */));
+    }
+
+    public List<String> fieldNames() {
+        return fields.stream().map(f -> f.name).collect(Collectors.toList());
+    }
+
+    public int length() {
+        return fields.size();
+    }
+
+    public StructField at(int index) {
+        return fields.get(index);
+    }
+
+    public String treeString() {
+        return "TODO";
+    }
+}