siddharthteotia commented on code in PR #9454: URL: https://github.com/apache/pinot/pull/9454#discussion_r983079883
########## pinot-segment-local/src/main/java/org/apache/pinot/segment/local/segment/index/loader/ForwardIndexHandler.java: ########## @@ -0,0 +1,273 @@ +/** + * 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.loader; + +import com.google.common.annotations.VisibleForTesting; +import com.google.common.base.Preconditions; +import java.io.File; +import java.math.BigDecimal; +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.Set; +import org.apache.commons.io.FileUtils; +import org.apache.pinot.segment.local.segment.readers.PinotSegmentColumnReader; +import org.apache.pinot.segment.spi.ColumnMetadata; +import org.apache.pinot.segment.spi.SegmentMetadata; +import org.apache.pinot.segment.spi.V1Constants; +import org.apache.pinot.segment.spi.compression.ChunkCompressionType; +import org.apache.pinot.segment.spi.creator.IndexCreationContext; +import org.apache.pinot.segment.spi.creator.IndexCreatorProvider; +import org.apache.pinot.segment.spi.creator.SegmentVersion; +import org.apache.pinot.segment.spi.index.creator.ForwardIndexCreator; +import org.apache.pinot.segment.spi.index.reader.ForwardIndexReader; +import org.apache.pinot.segment.spi.store.ColumnIndexType; +import org.apache.pinot.segment.spi.store.SegmentDirectory; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + + +/** + * Helper class used by {@link SegmentPreProcessor} to make changes to forward index and dictionary configs. Note + * that this handler only works for segment versions >= 3.0. Support for segment version < 3.0 is not added because + * majority of the usecases are in versions >= 3.0 and this avoids adding tech debt. The currently supported + * operations are: + * 1. Change compression on raw SV columns. + * + * TODO: Add support for the following: + * 1. Change compression for raw MV columns + * 2. Enable dictionary + * 3. Disable dictionary + */ +public class ForwardIndexHandler implements IndexHandler { + private static final Logger LOGGER = LoggerFactory.getLogger(ForwardIndexHandler.class); + + private final SegmentMetadata _segmentMetadata; + IndexLoadingConfig _indexLoadingConfig; + + protected enum Operation { + // TODO: Add other operations like ENABLE_DICTIONARY, DISABLE_DICTIONARY. + CHANGE_RAW_INDEX_COMPRESSION_TYPE, + } + + public ForwardIndexHandler(SegmentMetadata segmentMetadata, IndexLoadingConfig indexLoadingConfig) { + _segmentMetadata = segmentMetadata; + _indexLoadingConfig = indexLoadingConfig; + } + + @Override + public boolean needUpdateIndices(SegmentDirectory.Reader segmentReader) + throws Exception { + Map<String, Operation> columnOperationMap = computeOperation(segmentReader); + return !columnOperationMap.isEmpty(); + } + + @Override + public void updateIndices(SegmentDirectory.Writer segmentWriter, IndexCreatorProvider indexCreatorProvider) + throws Exception { + Map<String, Operation> columnOperationMap = computeOperation(segmentWriter); + if (columnOperationMap.isEmpty()) { + return; + } + + for (Map.Entry<String, Operation> entry : columnOperationMap.entrySet()) { + String column = entry.getKey(); + Operation operation = entry.getValue(); + + switch (operation) { + case CHANGE_RAW_INDEX_COMPRESSION_TYPE: + rewriteRawForwardIndex(column, segmentWriter, indexCreatorProvider); + break; + // TODO: Add other operations here. + default: + throw new IllegalStateException("Unsupported operation for column " + column); + } + } + } + + @VisibleForTesting + Map<String, Operation> computeOperation(SegmentDirectory.Reader segmentReader) + throws Exception { + Map<String, Operation> columnOperationMap = new HashMap<>(); + + // Does not work for segment versions < V3 + if (_segmentMetadata.getVersion().compareTo(SegmentVersion.v3) < 0) { + return columnOperationMap; + } + + // From existing column config. + Set<String> existingAllColumns = _segmentMetadata.getAllColumns(); + Set<String> existingDictColumns = + segmentReader.toSegmentDirectory().getColumnsWithIndex(ColumnIndexType.DICTIONARY); + Set<String> existingNoDictColumns = new HashSet<>(); + for (String column : existingAllColumns) { + if (!existingDictColumns.contains(column)) { + existingNoDictColumns.add(column); + } + } + + // From new column config. + Set<String> newNoDictColumns = _indexLoadingConfig.getNoDictionaryColumns(); + + for (String column : existingAllColumns) { + if (existingNoDictColumns.contains(column) && newNoDictColumns.contains(column)) { + // Both existing and new column is RAW forward index encoded. Check if compression needs to be changed. + if (shouldChangeCompressionType(column, segmentReader)) { + columnOperationMap.put(column, Operation.CHANGE_RAW_INDEX_COMPRESSION_TYPE); + } + } + } + + return columnOperationMap; + } + + private boolean shouldChangeCompressionType(String column, SegmentDirectory.Reader segmentReader) throws Exception { + ColumnMetadata existingColMetadata = _segmentMetadata.getColumnMetadataFor(column); + + // TODO: Remove this MV column limitation. + if (!existingColMetadata.isSingleValue()) { + return false; + } + + // The compression type for an existing segment can only be determined by reading the forward index header. + try (ForwardIndexReader fwdIndexReader = LoaderUtils.getForwardIndexReader(segmentReader, existingColMetadata)) { + ChunkCompressionType existingCompressionType = fwdIndexReader.getCompressionType(); + Preconditions.checkState(existingCompressionType != null, + "Existing compressionType cannot be null for raw forward index column=" + column); + + // Get the new compression type. + ChunkCompressionType newCompressionType = null; + Map<String, ChunkCompressionType> newCompressionConfigs = _indexLoadingConfig.getCompressionConfigs(); + if (newCompressionConfigs.containsKey(column)) { + newCompressionType = newCompressionConfigs.get(column); + } + + // Note that default compression type (PASS_THROUGH for metric and LZ4 for dimension) is not considered if the + // compressionType is not explicitly provided in tableConfig. This is to avoid incorrectly rewriting the all + // forward indexes during segmentReload when the default compressionType changes. + if (newCompressionType == null || existingCompressionType == newCompressionType) { + return false; + } + + return true; + } + } + + private void rewriteRawForwardIndex(String column, SegmentDirectory.Writer segmentWriter, + IndexCreatorProvider indexCreatorProvider) + throws Exception { + Preconditions.checkState(_segmentMetadata.getVersion() == SegmentVersion.v3); Review Comment: Can we put a TODO to remove this limitation ? I am not super sure if everyone in OSS has indeed migrated to v3. SegmentPreprocessor will only convert v1 to v3 if the tableConfig has v3 set otherwise it will leave as is. So, there is a chance of having some user still in v1 segment file format. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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