nssalian commented on code in PR #16827:
URL: https://github.com/apache/iceberg/pull/16827#discussion_r3779003615
##########
spark/v4.1/spark/src/test/java/org/apache/iceberg/spark/actions/TestSparkFileRewriteRunners.java:
##########
@@ -136,4 +136,38 @@ public void testInvalidValuesForZOrderDataOptions() {
.hasMessageContaining("Cannot use less than 1 byte for variable length
types with ZOrder")
.hasMessageContaining("'var-length-contribution' was set to 0");
}
+
+ @Test
+ public void testInvalidConstructorUsagesHilbertData() {
Review Comment:
Some enhancement suggestions: could you add a column-not-found case
(hilbert("nonexistent")) and a mixed identity+data case (hilbert("dep", "id"))
to testInvalidConstructorUsagesHilbertData, plus a zero-columns case
(hilbertIndex(new byte[0][], 8)) in TestHilbertByteUtils, to cover the "Cannot
find column", identity-filtering, and "zero columns" guards?
##########
core/src/main/java/org/apache/iceberg/util/HilbertByteUtils.java:
##########
@@ -0,0 +1,141 @@
+/*
+ * 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.util;
+
+import java.nio.ByteBuffer;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+
+/**
+ * Maps a set of columns (each already converted to fixed-width,
lexicographically-ordered unsigned
+ * bytes by {@link ZOrderByteUtils}) onto a single byte array whose unsigned
big-endian
+ * lexicographic ordering follows the multi-dimensional Hilbert space-filling
curve.
+ *
+ * <p>Unlike Z-ordering, the Hilbert transform requires every dimension to
contribute the same
+ * number of bits, so each column is read to a fixed {@code bitsPerColumn}
precision.
+ *
+ * <p>The transform is the standard "axes to transposed Hilbert index"
algorithm from J. Skilling,
+ * "Programming the Hilbert curve" (2004); the transposed index is then
serialized to a scalar with
Review Comment:
nit: do we want to copy the full reference with the citation here?
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