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Author: mutianf

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStub.java

@@ -395,9 +395,20 @@ public Map<String, String> extract(ReadRowsRequest readRowsRequest) {
  }
 
  /**
- * @param rowAdapter
- * @param <RowT>
- * @return
+ * Creates a callable chain to handle bulk ReadRows RPCs. This is meant to be used in ReadRows
+ * batcher. The chain will:
+ *
+ * <ul>
+ * <li>Convert a {@link Query} into a {@link com.google.bigtable.v2.ReadRowsRequest}.
+ * <li>Upon receiving the response stream, it will merge the {@link
+ * com.google.bigtable.v2.ReadRowsResponse.CellChunk}s in logical rows. The actual row
+ * implementation can be configured in by the {@code rowAdapter} parameter.
+ * <li>Retry/resume on failure.
+ * <li>Filter out marker rows.
+ * <li>Construct a {@link UnaryCallable} that will buffer the entire stream into memory before
+ * completing. If the stream is empty, then the list will be empty.
+ * <li>Add tracing & metrics.
+ * </ul>
  */
  private <RowT> UnaryCallable<Query, List<RowT>> createBulkReadRowsCallable(
  RowAdapter<RowT> rowAdapter) {
@@ -409,6 +420,8 @@ private <RowT> UnaryCallable<Query, List<RowT>> createBulkReadRowsCallable(
 
  SpanName span = getSpanName("ReadRows");
 
+ // TracedBatchingContextCallable needs to be the last in the callable chain so Batcher can pass
+ // a BatchedCallContext to add batching metrics to ApiTracer.
  UnaryCallable<Query, List<RowT>> traced =
  new TracedBatchedContextCallable<>(
  readRowsUserCallable.all(),
@@ -540,7 +553,7 @@ private UnaryCallable<BulkMutation, Void> createBulkMutateRowsCallable() {
  userFacing, settings.getHeaderTracer(), spanName.toString());
 
  // TracedBatchingContextCallable needs to be the last in the callable chain so Batcher can pass
- // batchingCallContext to add batching metrics to ApiTracer.
+ // a BatchedCallContext to add batching metrics to ApiTracer.
  UnaryCallable<BulkMutation, Void> batchingContextCallable =
  new TracedBatchedContextCallable<>(
  withHeaderTracer,