[HUDI-2938] Metadata table util to get latest file slices for reader/writers (#4218)

hudi-client/hudi-client-common/src/main/java/org/apache/hudi/metadata/HoodieBackedTableMetadataWriter.java

@@ -697,7 +697,6 @@ public abstract class HoodieBackedTableMetadataWriter implements HoodieTableMeta
       return;
     }
 
-
     // Trigger compaction with suffixes based on the same instant time. This ensures that any future
     // delta commits synced over will not have an instant time lesser than the last completed instant on the
     // metadata table.

hudi-client/hudi-flink-client/src/main/java/org/apache/hudi/metadata/FlinkHoodieBackedTableMetadataWriter.java

@@ -154,7 +154,7 @@ public class FlinkHoodieBackedTableMetadataWriter extends HoodieBackedTableMetad
    * The record is tagged with respective file slice's location based on its record key.
    */
   private List<HoodieRecord> prepRecords(List<HoodieRecord> records, String partitionName, int numFileGroups) {
-    List<FileSlice> fileSlices = HoodieTableMetadataUtil.loadPartitionFileGroupsWithLatestFileSlices(metadataMetaClient, partitionName, false);
+    List<FileSlice> fileSlices = HoodieTableMetadataUtil.getPartitionLatestFileSlices(metadataMetaClient, partitionName);
     ValidationUtils.checkArgument(fileSlices.size() == numFileGroups, String.format("Invalid number of file groups: found=%d, required=%d", fileSlices.size(), numFileGroups));
 
     return records.stream().map(r -> {

hudi-client/hudi-spark-client/src/main/java/org/apache/hudi/metadata/SparkHoodieBackedTableMetadataWriter.java

@@ -169,7 +169,7 @@ public class SparkHoodieBackedTableMetadataWriter extends HoodieBackedTableMetad
    * The record is tagged with respective file slice's location based on its record key.
    */
   private JavaRDD<HoodieRecord> prepRecords(JavaRDD<HoodieRecord> recordsRDD, String partitionName, int numFileGroups) {
-    List<FileSlice> fileSlices = HoodieTableMetadataUtil.loadPartitionFileGroupsWithLatestFileSlices(metadataMetaClient, partitionName, false);
+    List<FileSlice> fileSlices = HoodieTableMetadataUtil.getPartitionLatestFileSlices(metadataMetaClient, partitionName);
     ValidationUtils.checkArgument(fileSlices.size() == numFileGroups, String.format("Invalid number of file groups: found=%d, required=%d", fileSlices.size(), numFileGroups));
 
     return recordsRDD.map(r -> {

hudi-client/hudi-spark-client/src/test/java/org/apache/hudi/client/functional/TestHoodieBackedMetadata.java

@@ -424,10 +424,8 @@ public class TestHoodieBackedMetadata extends TestHoodieMetadataBase {
     });
   }
 
-
   /**
    * Tests that virtual key configs are honored in base files after compaction in metadata table.
-   *
    */
   @ParameterizedTest
   @ValueSource(booleans = {true, false})

hudi-common/src/main/java/org/apache/hudi/metadata/HoodieBackedTableMetadata.java

@@ -245,7 +245,7 @@ public class HoodieBackedTableMetadata extends BaseTableMetadata {
 
         // Metadata is in sync till the latest completed instant on the dataset
         HoodieTimer timer = new HoodieTimer().startTimer();
-        List<FileSlice> latestFileSlices = HoodieTableMetadataUtil.loadPartitionFileGroupsWithLatestFileSlices(metadataMetaClient, partitionName, true);
+        List<FileSlice> latestFileSlices = HoodieTableMetadataUtil.getPartitionLatestMergedFileSlices(metadataMetaClient, partitionName);
         if (latestFileSlices.size() == 0) {
           // empty partition
           return Pair.of(null, null);

hudi-common/src/main/java/org/apache/hudi/metadata/HoodieTableMetadataUtil.java

@@ -338,29 +338,65 @@ public class HoodieTableMetadataUtil {
   }
 
   /**
-   * Loads the list of file groups for a partition of the Metadata Table with latest file slices.
+   * Get the latest file slices for a Metadata Table partition. If the file slice is
+   * because of pending compaction instant, then merge the file slice with the one
+   * just before the compaction instant time. The list of file slices returned is
+   * sorted in the correct order of file group name.
    *
-   * The list of file slices returned is sorted in the correct order of file group name.
+   * @param metaClient - Instance of {@link HoodieTableMetaClient}.
-   * @param metaClient instance of {@link HoodieTableMetaClient}.
+   * @param partition  - The name of the partition whose file groups are to be loaded.
-   * @param partition The name of the partition whose file groups are to be loaded.
-   * @param isReader true if reader code path, false otherwise.
    * @return List of latest file slices for all file groups in a given partition.
    */
-  public static List<FileSlice> loadPartitionFileGroupsWithLatestFileSlices(HoodieTableMetaClient metaClient, String partition, boolean isReader) {
+  public static List<FileSlice> getPartitionLatestMergedFileSlices(HoodieTableMetaClient metaClient, String partition) {
-    LOG.info("Loading file groups for metadata table partition " + partition);
+    LOG.info("Loading latest merged file slices for metadata table partition " + partition);
+    return getPartitionFileSlices(metaClient, partition, true);
+  }
 
-    // If there are no commits on the metadata table then the table's default FileSystemView will not return any file
+  /**
-    // slices even though we may have initialized them.
+   * Get the latest file slices for a Metadata Table partition. The list of file slices
+   * returned is sorted in the correct order of file group name.
+   *
+   * @param metaClient - Instance of {@link HoodieTableMetaClient}.
+   * @param partition  - The name of the partition whose file groups are to be loaded.
+   * @return List of latest file slices for all file groups in a given partition.
+   */
+  public static List<FileSlice> getPartitionLatestFileSlices(HoodieTableMetaClient metaClient, String partition) {
+    LOG.info("Loading latest file slices for metadata table partition " + partition);
+    return getPartitionFileSlices(metaClient, partition, false);
+  }
+
+  /**
+   * Get the latest file slices for a given partition.
+   *
+   * @param metaClient      - Instance of {@link HoodieTableMetaClient}.
+   * @param partition       - The name of the partition whose file groups are to be loaded.
+   * @param mergeFileSlices - When enabled, will merge the latest file slices with the last known
+   *                        completed instant. This is useful for readers when there are pending
+   *                        compactions. MergeFileSlices when disabled, will return the latest file
+   *                        slices without any merging, and this is needed for the writers.
+   * @return List of latest file slices for all file groups in a given partition.
+   */
+  private static List<FileSlice> getPartitionFileSlices(HoodieTableMetaClient metaClient, String partition,
+                                                        boolean mergeFileSlices) {
+    // If there are no commits on the metadata table then the table's
+    // default FileSystemView will not return any file slices even
+    // though we may have initialized them.
     HoodieTimeline timeline = metaClient.getActiveTimeline();
     if (timeline.empty()) {
-      final HoodieInstant instant = new HoodieInstant(false, HoodieTimeline.DELTA_COMMIT_ACTION, HoodieActiveTimeline.createNewInstantTime());
+      final HoodieInstant instant = new HoodieInstant(false, HoodieTimeline.DELTA_COMMIT_ACTION,
+          HoodieActiveTimeline.createNewInstantTime());
       timeline = new HoodieDefaultTimeline(Arrays.asList(instant).stream(), metaClient.getActiveTimeline()::getInstantDetails);
     }
 
     HoodieTableFileSystemView fsView = new HoodieTableFileSystemView(metaClient, timeline);
-    Stream<FileSlice> fileSliceStream = isReader ? fsView.getLatestMergedFileSlicesBeforeOrOn(partition, timeline.filterCompletedInstants().lastInstant().get().getTimestamp()) :
+    Stream<FileSlice> fileSliceStream;
-        fsView.getLatestFileSlices(partition);
+    if (mergeFileSlices) {
-    return fileSliceStream.sorted((s1, s2) -> s1.getFileId().compareTo(s2.getFileId()))
+      fileSliceStream = fsView.getLatestMergedFileSlicesBeforeOrOn(
-        .collect(Collectors.toList());
+          partition, timeline.filterCompletedInstants().lastInstant().get().getTimestamp());
+    } else {
+      fileSliceStream = fsView.getLatestFileSlices(partition);
     }
+    return fileSliceStream.sorted((s1, s2) -> s1.getFileId().compareTo(s2.getFileId())).collect(Collectors.toList());
+  }
+
 }