xiangfu0 commented on code in PR #18092:
URL: https://github.com/apache/pinot/pull/18092#discussion_r3036488543
##########
pinot-segment-local/src/main/java/org/apache/pinot/segment/local/segment/index/forward/ForwardIndexType.java:
##########
@@ -113,6 +113,8 @@ private void validateForwardIndexEnabled(ForwardIndexConfig
forwardIndexConfig,
if (dictionaryConfig.isEnabled()) {
Preconditions.checkState(compressionCodec == null ||
compressionCodec.isApplicableToDictEncodedIndex(),
"Compression codec: %s is not applicable to dictionary encoded
column: %s", compressionCodec, column);
+ Preconditions.checkState(forwardIndexConfig.getTransformCodec() == null,
+ "Transform codec is not supported for dictionary-encoded column:
%s", column);
Review Comment:
This is no longer applicable — `TransformCodec` was removed. The codec
pipeline is now a `ChunkCodecPipeline` (list of `ChunkCodec` stages), and
dictionary-encoded columns never have a pipeline set.
##########
pinot-segment-spi/src/main/java/org/apache/pinot/segment/spi/compression/TransformCodec.java:
##########
@@ -0,0 +1,67 @@
+/**
+ * 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.pinot.segment.spi.compression;
+
+/**
+ * Enum representing reversible numeric transforms that can be applied to
chunk data before compression.
+ * Unlike {@link ChunkCompressionType}, which defines byte-level compression
algorithms, TransformCodec
+ * operates on typed numeric values (INT/LONG) to reduce entropy before the
compression stage.
+ *
+ * <p>The transform is applied per-chunk: each chunk is independently
transformed and compressed.
+ * On read, the reverse transform is applied after decompression.</p>
+ *
+ * <p>Supported in V1 for single-value INT and LONG RAW forward index columns
only.</p>
+ */
+public enum TransformCodec {
+
+ /** No transform applied. */
+ NONE(0),
+
+ /**
+ * Delta encoding: stores the first value as-is, then each subsequent value
as the difference
+ * from the previous value. Effective for monotonically increasing data
(e.g., timestamps).
+ */
+ DELTA(1),
+
+ /**
+ * Double-delta encoding: stores the first value as-is, the first delta
as-is, then each
+ * subsequent value as the difference of consecutive deltas. Effective for
data with constant
+ * or near-constant step sizes (e.g., fixed-interval timestamps).
+ */
+ DOUBLE_DELTA(2);
+
+ private static final TransformCodec[] VALUES = values();
+
+ private final int _value;
+
+ TransformCodec(int value) {
+ _value = value;
+ }
+
+ public int getValue() {
+ return _value;
+ }
+
+ public static TransformCodec valueOf(int ordinal) {
+ if (ordinal < 0 || ordinal >= VALUES.length) {
+ throw new IllegalArgumentException("Invalid TransformCodec ordinal: " +
ordinal);
+ }
+ return VALUES[ordinal];
+ }
Review Comment:
No longer applicable — `TransformCodec` was removed entirely. The new
`ChunkCodec` enum uses an explicit `fromValue(int)` method that iterates over
all enum values and matches by `_value`, so it's safe against reordering.
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