jihoonson commented on a change in pull request #12279: URL: https://github.com/apache/druid/pull/12279#discussion_r826540489
########## File path: processing/src/main/java/org/apache/druid/segment/serde/NullColumnPartSerde.java ########## @@ -0,0 +1,212 @@ +/* + * 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.druid.segment.serde; + +import com.fasterxml.jackson.annotation.JsonCreator; +import com.fasterxml.jackson.annotation.JsonProperty; +import com.google.common.base.Suppliers; +import org.apache.druid.java.util.common.io.smoosh.FileSmoosher; +import org.apache.druid.query.extraction.ExtractionFn; +import org.apache.druid.segment.DimensionSelector; +import org.apache.druid.segment.column.BitmapIndex; +import org.apache.druid.segment.column.BitmapIndexes; +import org.apache.druid.segment.column.DictionaryEncodedColumn; +import org.apache.druid.segment.data.BitmapSerdeFactory; +import org.apache.druid.segment.data.IndexedInts; +import org.apache.druid.segment.data.ReadableOffset; +import org.apache.druid.segment.vector.MultiValueDimensionVectorSelector; +import org.apache.druid.segment.vector.NilVectorSelector; +import org.apache.druid.segment.vector.ReadableVectorOffset; +import org.apache.druid.segment.vector.SingleValueDimensionVectorSelector; + +import javax.annotation.Nullable; +import java.nio.channels.WritableByteChannel; +import java.util.Objects; + +/** + * A ColumnPartSerde to read and write null-only columns. + * Its serializer is no-op as nothing is stored for null-only columns. + * Its deserializer creates necessary column metadata and indexes when the column is read. + */ +public class NullColumnPartSerde implements ColumnPartSerde +{ + private static final Serializer NOOP_SERIALIZER = new Serializer() + { + @Override + public long getSerializedSize() + { + return 0; + } + + @Override + public void writeTo(WritableByteChannel channel, FileSmoosher smoosher) + { + } + }; + + private final int numRows; + private final BitmapSerdeFactory bitmapSerdeFactory; + private final NullDictionaryEncodedColumn nullDictionaryEncodedColumn; + private final BitmapIndex bitmapIndex; + + @JsonCreator + public NullColumnPartSerde( + @JsonProperty("numRows") int numRows, + @JsonProperty("bitmapSerdeFactory") BitmapSerdeFactory bitmapSerdeFactory + ) + { + this.numRows = numRows; + this.bitmapSerdeFactory = bitmapSerdeFactory; + this.nullDictionaryEncodedColumn = new NullDictionaryEncodedColumn(); + this.bitmapIndex = BitmapIndexes.forNilColumn(() -> numRows, bitmapSerdeFactory.getBitmapFactory()); + } + + @JsonProperty + public int getNumRows() + { + return numRows; + } + + @JsonProperty + public BitmapSerdeFactory getBitmapSerdeFactory() + { + return bitmapSerdeFactory; + } + + @Nullable + @Override + public Serializer getSerializer() + { + return NOOP_SERIALIZER; + } + + @Override + public Deserializer getDeserializer() + { + return (buffer, builder, columnConfig) -> { + builder + .setHasMultipleValues(false) + .setHasNulls(true) + .setFilterable(true) + .setBitmapIndex(Suppliers.ofInstance(bitmapIndex)); + builder.setDictionaryEncodedColumnSupplier(Suppliers.ofInstance(nullDictionaryEncodedColumn)); + }; + } + + @Override + public boolean equals(Object o) + { + if (this == o) { + return true; + } + if (o == null || getClass() != o.getClass()) { + return false; + } + NullColumnPartSerde partSerde = (NullColumnPartSerde) o; + return numRows == partSerde.numRows + && bitmapSerdeFactory.equals(partSerde.bitmapSerdeFactory); + } + + @Override + public int hashCode() + { + return Objects.hash(numRows, bitmapSerdeFactory); + } + + private final class NullDictionaryEncodedColumn implements DictionaryEncodedColumn<String> + { + // Get the singleton instance of DimensionSelector.NullDimensionSelectorHolder.NullDimensionSelector + // to reuse its dictionary lookup logic. + private final DimensionSelector nullDimensionSelector = DimensionSelector.constant(null); + + @Override + public int length() + { + return numRows; + } + + @Override + public boolean hasMultipleValues() + { + return false; + } + + @Override + public int getSingleValueRow(int rowNum) + { + throw new RuntimeException("This method should not be called for null-only columns"); + } + + @Override + public IndexedInts getMultiValueRow(int rowNum) + { + throw new RuntimeException("This method should not be called for null-only columns"); + } + + @Nullable + @Override + public String lookupName(int id) + { + return nullDimensionSelector.lookupName(id); + } + + @Override + public int lookupId(String name) + { + return nullDimensionSelector.idLookup().lookupId(name); + } + + @Override + public int getCardinality() + { + return 1; + } + + @Override + public DimensionSelector makeDimensionSelector( + ReadableOffset offset, + @Nullable ExtractionFn extractionFn + ) + { + return DimensionSelector.constant(null, extractionFn); + } + + @Override + public SingleValueDimensionVectorSelector makeSingleValueDimensionVectorSelector( + ReadableVectorOffset vectorOffset + ) + { + return NilVectorSelector.create(vectorOffset); + } + + @Override + public MultiValueDimensionVectorSelector makeMultiValueDimensionVectorSelector( + ReadableVectorOffset vectorOffset + ) + { + throw new RuntimeException("This method should not be called for null-only columns"); + } + Review comment: I don't think they are strictly necessary in this PR since numeric columns don't use `NullColumnPartSerde` yet even when it's completely empty as it's noted in the "Future work" section of the PR description. If you agree, I'd like to add them in a follow-up PR when I fix numeric columns. -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
