fix(bigtable): reject empty split points in RowSetUtil and clarify QueryPaginator Javadoc

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/internal/RowSetUtil.java

@@ -51,6 +51,7 @@ private RowSetUtil() {}
 
   /** Removes the {@code #excludePoint} rowkey from the {@code RowSet} */
   public static RowSet eraseLargeRow(RowSet rowSet, ByteString excludePoint) {
+    Preconditions.checkArgument(!excludePoint.isEmpty(), "Can't handle empty excludePoint");
 
     RowSet.Builder newRowSet = RowSet.newBuilder();
 
@@ -89,6 +90,7 @@ public static RowSet eraseLargeRow(RowSet rowSet, ByteString excludePoint) {
    * removed. The primary usecase is to resume a broken ReadRows stream.
    */
   public static RowSet erase(RowSet rowSet, ByteString splitPoint, boolean fromStart) {
+    Preconditions.checkArgument(!splitPoint.isEmpty(), "Can't handle empty splitPoint");
     RowSet.Builder newRowSet = RowSet.newBuilder();
 
     if (rowSet.getRowKeysList().isEmpty() && rowSet.getRowRangesList().isEmpty()) {

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/models/Query.java

@@ -292,13 +292,13 @@ public List<Query> shard(SortedSet<ByteString> splitPoints) {
    *
    * <pre>{@code
    * Query query = Query.create(...).range("a", "z");
-   * Query.QueryPaginator paginator = query.createQueryPaginator(100);
+   * Query.QueryPaginator paginator = query.createPaginator(100);
    * ByteString lastSeenRowKey = ByteString.EMPTY;
    * do {
    *     List<Row> rows = client.readRowsCallable().all().call(paginator.getNextQuery());
    *     for (Row row : rows) {
    *        // do some processing
-   *        lastSeenRow = row;
+   *        lastSeenRowKey = row.getKey();
    *     }
    * } while (paginator.advance(lastSeenRowKey));
    * }</pre>
@@ -440,6 +440,12 @@ public Query getNextQuery() {
     /**
      * Construct the next query. Return true if there are more queries to return. False if we've
      * read everything.
+     *
+     * @param lastSeenRowKey the key of the last row received across the pagination loop. Initialize
+     *     this to {@link ByteString#EMPTY} before the loop and update it as each row is read (see
+     *     {@link #createPaginator(int)}). If the first page is empty, {@link ByteString#EMPTY}
+     *     signals completion; if a subsequent page is empty, passing the unchanged key from the
+     *     previous page signals completion.
      */
     public boolean advance(@Nonnull ByteString lastSeenRowKey) {
       Preconditions.checkNotNull(

java-bigtable/google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/internal/RowSetUtilTest.java

@@ -16,6 +16,7 @@
 package com.google.cloud.bigtable.data.v2.internal;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
 
 import com.google.bigtable.v2.RowRange;
 import com.google.bigtable.v2.RowSet;
@@ -344,4 +345,20 @@ public void eraseLargeRowEmptyRangeTest() {
     RowSet actual = RowSetUtil.eraseLargeRow(rowSet, key);
     assertThat(actual).isNull();
   }
+
+  @Test
+  public void testEraseEmptyKey() {
+    RowSet rowSet = RowSet.getDefaultInstance();
+    assertThrows(
+        IllegalArgumentException.class, () -> RowSetUtil.erase(rowSet, ByteString.EMPTY, true));
+    assertThrows(
+        IllegalArgumentException.class, () -> RowSetUtil.erase(rowSet, ByteString.EMPTY, false));
+  }
+
+  @Test
+  public void testEraseLargeRowEmptyKey() {
+    RowSet rowSet = RowSet.getDefaultInstance();
+    assertThrows(
+        IllegalArgumentException.class, () -> RowSetUtil.eraseLargeRow(rowSet, ByteString.EMPTY));
+  }
 }