Support reading tables with only Hive metadata (#23)

* Support reading tables with Hive metadata if Iceberg metadata is not available

core/src/main/java/org/apache/iceberg/BaseFileScanTask.java

@@ -29,15 +29,15 @@
 import org.apache.iceberg.expressions.Expression;
 import org.apache.iceberg.expressions.ResidualEvaluator;
 
-class BaseFileScanTask implements FileScanTask {
+public class BaseFileScanTask implements FileScanTask {
   private final DataFile file;
   private final String schemaString;
   private final String specString;
   private final ResidualEvaluator residuals;
 
   private transient PartitionSpec spec = null;
 
-  BaseFileScanTask(DataFile file, String schemaString, String specString, ResidualEvaluator residuals) {
+  public BaseFileScanTask(DataFile file, String schemaString, String specString, ResidualEvaluator residuals) {
     this.file = file;
     this.schemaString = schemaString;
     this.specString = specString;

core/src/main/java/org/apache/iceberg/BaseMetastoreCatalog.java

@@ -177,7 +177,7 @@ private Table loadMetadataTable(TableIdentifier identifier) {
     }
   }
 
-  private boolean isValidMetadataIdentifier(TableIdentifier identifier) {
+  protected boolean isValidMetadataIdentifier(TableIdentifier identifier) {
     return MetadataTableType.from(identifier.name()) != null &&
         isValidIdentifier(TableIdentifier.of(identifier.namespace().levels()));
   }
@@ -275,7 +275,7 @@ private static void deleteFiles(FileIO io, Set<ManifestFile> allManifests) {
         });
   }
 
-  private static String fullTableName(String catalogName, TableIdentifier identifier) {
+  protected static String fullTableName(String catalogName, TableIdentifier identifier) {
     StringBuilder sb = new StringBuilder();
 
     if (catalogName.contains("/") || catalogName.contains(":")) {

core/src/main/java/org/apache/iceberg/BaseMetastoreTableOperations.java

@@ -270,4 +270,13 @@ private void deleteRemovedMetadataFiles(TableMetadata base, TableMetadata metada
           .run(previousMetadataFile -> io().deleteFile(previousMetadataFile.file()));
     }
   }
+
+  protected void setCurrentMetadata(TableMetadata currentMetadata) {
+    this.currentMetadata = currentMetadata;
+  }
+
+  protected void setShouldRefresh(boolean shouldRefresh) {
+    this.shouldRefresh = shouldRefresh;
+  }
+
 }

hive/src/main/java/org/apache/iceberg/hive/HiveCatalogs.java

@@ -25,6 +25,7 @@
 import java.util.concurrent.TimeUnit;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hive.conf.HiveConf;
+import org.apache.iceberg.hive.legacy.LegacyHiveCatalog;
 
 public final class HiveCatalogs {
 
@@ -39,6 +40,11 @@ public final class HiveCatalogs {
           .removalListener((RemovalListener<String, HiveCatalog>) (uri, catalog, cause) -> catalog.close())
           .build();
 
+  private static final Cache<String, HiveCatalog> LEGACY_CATALOG_CACHE = Caffeine.newBuilder()
+      .expireAfterAccess(10, TimeUnit.MINUTES)
+      .removalListener((RemovalListener<String, HiveCatalog>) (uri, catalog, cause) -> catalog.close())
+      .build();
+
   private HiveCatalogs() {}
 
   public static HiveCatalog loadCatalog(Configuration conf) {
@@ -47,6 +53,12 @@ public static HiveCatalog loadCatalog(Configuration conf) {
     return CATALOG_CACHE.get(metastoreUri, uri -> new HiveCatalog(conf));
   }
 
+  public static HiveCatalog loadLegacyCatalog(Configuration conf) {
+    // metastore URI can be null in local mode
+    String metastoreUri = conf.get(HiveConf.ConfVars.METASTOREURIS.varname, "");
+    return LEGACY_CATALOG_CACHE.get(metastoreUri, uri -> new LegacyHiveCatalog(conf));
+  }
+
   /**
    * @deprecated Use {@link #loadHiveMetadataPreservingCatalog(Configuration)} instead
    */

hive/src/main/java/org/apache/iceberg/hive/HiveMetadataPreservingTableOperations.java

@@ -83,6 +83,7 @@ protected void doRefresh() {
           String errMsg = String.format("%s.%s is missing %s property", database, tableName, METADATA_LOCATION_PROP);
           throw new IllegalArgumentException(errMsg);
         }
+
         if (!io().newInputFile(metadataLocation).exists()) {
           String errMsg = String.format("%s property for %s.%s points to a non-existent file %s",
               METADATA_LOCATION_PROP, database, tableName, metadataLocation);

hive/src/main/java/org/apache/iceberg/hive/HiveTableOperations.java

@@ -113,6 +113,11 @@ protected void doRefresh() {
         throw new IllegalArgumentException(errMsg);
       }
 
+      if (!io().newInputFile(metadataLocation).exists()) {
+        String errMsg = String.format("%s property for %s.%s points to a non-existent file %s",
+            METADATA_LOCATION_PROP, database, tableName, metadataLocation);
+        throw new IllegalArgumentException(errMsg);
+      }
     } catch (NoSuchObjectException e) {
       if (currentMetadataLocation() != null) {
         throw new NoSuchTableException(String.format("No such table: %s.%s", database, tableName));

hive/src/main/java/org/apache/iceberg/hive/legacy/DirectoryInfo.java

@@ -0,0 +1,51 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.iceberg.hive.legacy;
+
+import org.apache.iceberg.FileFormat;
+import org.apache.iceberg.StructLike;
+
+
+/**
+ * Metadata for a data directory referenced by either a Hive table or a partition
+ */
+class DirectoryInfo {
+  private final String location;
+  private final FileFormat format;
+  private final StructLike partitionData;
+
+  DirectoryInfo(String location, FileFormat format, StructLike partitionData) {
+    this.location = location;
+    this.format = format;
+    this.partitionData = partitionData;
+  }
+
+  public String location() {
+    return location;
+  }
+
+  public FileFormat format() {
+    return format;
+  }
+
+  public StructLike partitionData() {
+    return partitionData;
+  }
+}

hive/src/main/java/org/apache/iceberg/hive/legacy/FileSystemUtils.java

@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.iceberg.hive.legacy;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.PathFilter;
+import org.apache.iceberg.exceptions.RuntimeIOException;
+
+
+class FileSystemUtils {
+
+  private FileSystemUtils() {}
+
+  /**
+   * Lists all non-hidden files for the given directory
+   */
+  static List<FileStatus> listFiles(String directory, Configuration conf) {
+
+    final Path directoryPath = new Path(directory);
+    final FileStatus[] files;
+    try {
+      FileSystem fs = directoryPath.getFileSystem(conf);
+      files = fs.listStatus(directoryPath, HiddenPathFilter.INSTANCE);
+    } catch (IOException e) {
+      throw new RuntimeIOException(e, "Error listing files for directory: " + directory);
+    }
+    return Arrays.asList(files);
+  }
+
+  private enum HiddenPathFilter implements PathFilter {
+    INSTANCE;
+
+    @Override
+    public boolean accept(Path path) {
+      return !path.getName().startsWith("_") && !path.getName().startsWith(".");
+    }
+  }
+}