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Introduce raw fwd index version V5 containing implicit num doc length…
…, improving space efficiency (#14105)
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.../java/org/apache/pinot/segment/local/io/writer/impl/VarByteChunkForwardIndexWriterV5.java
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| /** | ||
| * 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.local.io.writer.impl; | ||
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| import java.io.File; | ||
| import java.io.IOException; | ||
| import javax.annotation.concurrent.NotThreadSafe; | ||
| import org.apache.pinot.segment.local.utils.ArraySerDeUtils; | ||
| import org.apache.pinot.segment.spi.compression.ChunkCompressionType; | ||
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| /** | ||
| * Forward index writer that extends {@link VarByteChunkForwardIndexWriterV4} and overrides the data layout for | ||
| * multi-value fixed byte operations to improve space efficiency. | ||
| * | ||
| * <p>Consider the following multi-value document as an example: {@code [int(1), int(2), int(3)]}. | ||
| * The current binary data layout in {@code VarByteChunkForwardIndexWriterV4} is as follows:</p> | ||
| * <pre> | ||
| * 0x00000010 0x00000003 0x00000001 0x00000002 0x00000003 | ||
| * </pre> | ||
| * | ||
| * <ol> | ||
| * <li>The first 4 bytes ({@code 0x00000010}) represent the total payload length of the byte array | ||
| * containing the multi-value document content, which in this case is 16 bytes.</li> | ||
| * | ||
| * <li>The next 4 bytes ({@code 0x00000003}) represent the number of elements in the multi-value document (i.e., 3) | ||
| * .</li> | ||
| * | ||
| * <li>The remaining 12 bytes ({@code 0x00000001 0x00000002 0x00000003}) represent the 3 integer values of the | ||
| * multi-value document: 1, 2, and 3.</li> | ||
| * </ol> | ||
| * | ||
| * <p>In Pinot, the fixed byte raw forward index can only store one specific fixed-length data type: | ||
| * {@code int}, {@code long}, {@code float}, or {@code double}. Instead of explicitly storing the number of elements | ||
| * for each document for multi-value document, this value can be inferred by:</p> | ||
| * <pre> | ||
| * number of elements = buffer payload length / size of data type | ||
| * </pre> | ||
| * | ||
| * <p>If the forward index uses the passthrough chunk compression type (i.e., no compression), we can save | ||
| * 4 bytes per document by omitting the explicit element count. This leads to the following space savings:</p> | ||
| * | ||
| * <ul> | ||
| * <li>For documents with 0 elements, we save 50%.</li> | ||
| * <li>For documents with 1 element, we save 33%.</li> | ||
| * <li>For documents with 2 elements, we save 25%.</li> | ||
| * <li>As the number of elements increases, the percentage of space saved decreases.</li> | ||
| * </ul> | ||
| * | ||
| * <p>For forward indexes that use compression to reduce data size, the savings can be even more significant | ||
| * in certain cases. This is demonstrated in the unit test {@link VarByteChunkV5Test#validateCompressionRatioIncrease}, | ||
| * where ZStandard was used as the chunk compressor. In the test, 1 million short multi-value (MV) documents | ||
| * were inserted, following a Gaussian distribution for document lengths. Additionally, the values of each integer | ||
| * in the MV documents were somewhat repetitive. Under these conditions, we observed a 50%+ reduction in on-disk | ||
| * file size compared to the V4 forward index writer version.</p> | ||
| * | ||
| * <p>Note that the {@code VERSION} tag is a {@code static final} class variable set to {@code 5}. Since static | ||
| * variables are shadowed in the child class thus associated with the class that defines them, care must be taken to | ||
| * ensure that the parent class can correctly observe the child class's {@code VERSION} value at runtime. To handle | ||
| * this cleanly and correctly, the {@code getVersion()} method is overridden to return the concrete subclass's | ||
| * {@code VERSION} value, ensuring that the correct version number is returned even when using a reference to the | ||
| * parent class.</p> | ||
| * | ||
| * @see VarByteChunkForwardIndexWriterV4 | ||
| * @see VarByteChunkForwardIndexWriterV5#getVersion() | ||
| */ | ||
| @NotThreadSafe | ||
| public class VarByteChunkForwardIndexWriterV5 extends VarByteChunkForwardIndexWriterV4 { | ||
| public static final int VERSION = 5; | ||
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| public VarByteChunkForwardIndexWriterV5(File file, ChunkCompressionType compressionType, int chunkSize) | ||
| throws IOException { | ||
| super(file, compressionType, chunkSize); | ||
| } | ||
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| // Override the parent class getVersion(); | ||
| @Override | ||
| public int getVersion() { | ||
| return VERSION; | ||
| } | ||
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| @Override | ||
| public void putIntMV(int[] values) { | ||
| putBytes(ArraySerDeUtils.serializeIntArrayWithoutLength(values)); | ||
| } | ||
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| @Override | ||
| public void putLongMV(long[] values) { | ||
| putBytes(ArraySerDeUtils.serializeLongArrayWithoutLength(values)); | ||
| } | ||
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| @Override | ||
| public void putFloatMV(float[] values) { | ||
| putBytes(ArraySerDeUtils.serializeFloatArrayWithoutLength(values)); | ||
| } | ||
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| @Override | ||
| public void putDoubleMV(double[] values) { | ||
| putBytes(ArraySerDeUtils.serializeDoubleArrayWithoutLength(values)); | ||
| } | ||
| } |
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83 changes: 83 additions & 0 deletions
83
...e/pinot/segment/local/segment/index/readers/forward/VarByteChunkForwardIndexReaderV5.java
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| @@ -0,0 +1,83 @@ | ||
| /** | ||
| * 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.local.segment.index.readers.forward; | ||
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| import org.apache.pinot.segment.local.io.writer.impl.VarByteChunkForwardIndexWriterV4; | ||
| import org.apache.pinot.segment.local.io.writer.impl.VarByteChunkForwardIndexWriterV5; | ||
| import org.apache.pinot.segment.local.utils.ArraySerDeUtils; | ||
| import org.apache.pinot.segment.spi.memory.PinotDataBuffer; | ||
| import org.apache.pinot.spi.data.FieldSpec; | ||
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| /** | ||
| * Chunk-based raw (non-dictionary-encoded) forward index reader for values of SV variable length data types | ||
| * (BIG_DECIMAL, STRING, BYTES), MV fixed length and MV variable length data types. | ||
| * <p>For data layout, please refer to the documentation for {@link VarByteChunkForwardIndexWriterV4} | ||
| */ | ||
| public class VarByteChunkForwardIndexReaderV5 extends VarByteChunkForwardIndexReaderV4 { | ||
| public VarByteChunkForwardIndexReaderV5(PinotDataBuffer dataBuffer, FieldSpec.DataType storedType, | ||
| boolean isSingleValue) { | ||
| super(dataBuffer, storedType, isSingleValue); | ||
| } | ||
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| @Override | ||
| public int getVersion() { | ||
| return VarByteChunkForwardIndexWriterV5.VERSION; | ||
| } | ||
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| @Override | ||
| public int getIntMV(int docId, int[] valueBuffer, VarByteChunkForwardIndexReaderV4.ReaderContext context) { | ||
| return ArraySerDeUtils.deserializeIntArrayWithoutLength(context.getValue(docId), valueBuffer); | ||
| } | ||
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| @Override | ||
| public int[] getIntMV(int docId, VarByteChunkForwardIndexReaderV4.ReaderContext context) { | ||
| return ArraySerDeUtils.deserializeIntArrayWithoutLength(context.getValue(docId)); | ||
| } | ||
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| @Override | ||
| public int getLongMV(int docId, long[] valueBuffer, VarByteChunkForwardIndexReaderV4.ReaderContext context) { | ||
| return ArraySerDeUtils.deserializeLongArrayWithoutLength(context.getValue(docId), valueBuffer); | ||
| } | ||
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| @Override | ||
| public long[] getLongMV(int docId, VarByteChunkForwardIndexReaderV4.ReaderContext context) { | ||
| return ArraySerDeUtils.deserializeLongArrayWithoutLength(context.getValue(docId)); | ||
| } | ||
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| @Override | ||
| public int getFloatMV(int docId, float[] valueBuffer, VarByteChunkForwardIndexReaderV4.ReaderContext context) { | ||
| return ArraySerDeUtils.deserializeFloatArrayWithoutLength(context.getValue(docId), valueBuffer); | ||
| } | ||
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| @Override | ||
| public float[] getFloatMV(int docId, VarByteChunkForwardIndexReaderV4.ReaderContext context) { | ||
| return ArraySerDeUtils.deserializeFloatArrayWithoutLength(context.getValue(docId)); | ||
| } | ||
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| @Override | ||
| public int getDoubleMV(int docId, double[] valueBuffer, VarByteChunkForwardIndexReaderV4.ReaderContext context) { | ||
| return ArraySerDeUtils.deserializeDoubleArrayWithoutLength(context.getValue(docId), valueBuffer); | ||
| } | ||
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| @Override | ||
| public double[] getDoubleMV(int docId, VarByteChunkForwardIndexReaderV4.ReaderContext context) { | ||
| return ArraySerDeUtils.deserializeDoubleArrayWithoutLength(context.getValue(docId)); | ||
| } | ||
| } |
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