Introduce FallbackSyntheticSourceBlockLoader and apply it to keyword fields #119546
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| /* | ||
| * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one | ||
| * or more contributor license agreements. Licensed under the "Elastic License | ||
| * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side | ||
| * Public License v 1"; you may not use this file except in compliance with, at | ||
| * your election, the "Elastic License 2.0", the "GNU Affero General Public | ||
| * License v3.0 only", or the "Server Side Public License, v 1". | ||
| */ | ||
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| package org.elasticsearch.index.mapper; | ||
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| import org.apache.lucene.index.LeafReaderContext; | ||
| import org.apache.lucene.index.SortedSetDocValues; | ||
| import org.elasticsearch.search.fetch.StoredFieldsSpec; | ||
| import org.elasticsearch.xcontent.XContentParser; | ||
| import org.elasticsearch.xcontent.XContentParserConfiguration; | ||
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| import java.io.IOException; | ||
| import java.util.ArrayList; | ||
| import java.util.HashMap; | ||
| import java.util.HashSet; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.Optional; | ||
| import java.util.Set; | ||
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| /** | ||
| * Block loader for fields that use fallback synthetic source implementation. | ||
| * <br> | ||
| * Usually fields have doc_values or stored fields and block loaders use them directly. In some cases neither is available | ||
| * and we would fall back to (potentially synthetic) _source. However, in case of synthetic source, there is actually no need to | ||
| * construct the entire _source. We know that there is no doc_values and stored fields, and therefore we will be using fallback synthetic | ||
| * source. That is equivalent to just reading _ignored_source stored field directly and doing an in-place synthetic source just | ||
| * for this field. | ||
| * <br> | ||
| * See {@link IgnoredSourceFieldMapper}. | ||
| */ | ||
| public abstract class FallbackSyntheticSourceBlockLoader implements BlockLoader { | ||
| private final Reader<?> reader; | ||
| private final String fieldName; | ||
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| protected FallbackSyntheticSourceBlockLoader(Reader<?> reader, String fieldName) { | ||
| this.reader = reader; | ||
| this.fieldName = fieldName; | ||
| } | ||
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| @Override | ||
| public ColumnAtATimeReader columnAtATimeReader(LeafReaderContext context) throws IOException { | ||
| return null; | ||
| } | ||
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| @Override | ||
| public RowStrideReader rowStrideReader(LeafReaderContext context) throws IOException { | ||
| return new IgnoredSourceRowStrideReader<>(fieldName, reader); | ||
| } | ||
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| @Override | ||
| public StoredFieldsSpec rowStrideStoredFieldSpec() { | ||
| return new StoredFieldsSpec(false, false, Set.of(IgnoredSourceFieldMapper.NAME)); | ||
| } | ||
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| @Override | ||
| public boolean supportsOrdinals() { | ||
| return false; | ||
| } | ||
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| @Override | ||
| public SortedSetDocValues ordinals(LeafReaderContext context) throws IOException { | ||
| throw new UnsupportedOperationException(); | ||
| } | ||
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| private record IgnoredSourceRowStrideReader<T>(String fieldName, Reader<T> reader) implements RowStrideReader { | ||
| @Override | ||
| public void read(int docId, StoredFields storedFields, Builder builder) throws IOException { | ||
| var ignoredSource = storedFields.storedFields().get(IgnoredSourceFieldMapper.NAME); | ||
| if (ignoredSource == null) { | ||
| return; | ||
| } | ||
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| Map<String, List<IgnoredSourceFieldMapper.NameValue>> valuesForFieldAndParents = new HashMap<>(); | ||
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| // Contains name of the field and all its parents | ||
| Set<String> fieldNames = new HashSet<>() { | ||
| { | ||
| add("_doc"); | ||
| } | ||
| }; | ||
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| var current = new StringBuilder(); | ||
| for (String part : fieldName.split("\\.")) { | ||
| current.append(part); | ||
| fieldNames.add(current.toString()); | ||
| } | ||
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| for (Object value : ignoredSource) { | ||
| IgnoredSourceFieldMapper.NameValue nameValue = IgnoredSourceFieldMapper.decode(value); | ||
| if (fieldNames.contains(nameValue.name())) { | ||
| valuesForFieldAndParents.computeIfAbsent(nameValue.name(), k -> new ArrayList<>()).add(nameValue); | ||
| } | ||
| } | ||
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| // TODO figure out how to handle XContentDataHelper#voidValue() | ||
|
There was a problem hiding this comment. iirc voidValue means to ignore ignored source, because we do have values in doc values for a field? I'm trying to remember in what cases we use void value. There was a problem hiding this comment.
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| var blockValues = new ArrayList<T>(); | ||
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| var leafFieldValue = valuesForFieldAndParents.get(fieldName); | ||
| if (leafFieldValue != null) { | ||
| readFromFieldValue(leafFieldValue, blockValues); | ||
| } else { | ||
| readFromParentValue(valuesForFieldAndParents, blockValues); | ||
| } | ||
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| if (blockValues.isEmpty() == false) { | ||
| if (blockValues.size() > 1) { | ||
| builder.beginPositionEntry(); | ||
| } | ||
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| reader.writeToBlock(blockValues, builder); | ||
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| if (blockValues.size() > 1) { | ||
| builder.endPositionEntry(); | ||
| } | ||
| } else { | ||
| builder.appendNull(); | ||
| } | ||
| } | ||
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| private void readFromFieldValue(List<IgnoredSourceFieldMapper.NameValue> nameValues, List<T> blockValues) throws IOException { | ||
| if (nameValues.isEmpty()) { | ||
| return; | ||
| } | ||
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| for (var nameValue : nameValues) { | ||
| // Leaf field is stored directly (not as a part of a parent object), let's try to decode it. | ||
| Optional<Object> singleValue = XContentDataHelper.decode(nameValue.value()); | ||
| if (singleValue.isPresent()) { | ||
| reader.convertValue(singleValue.get(), blockValues); | ||
| continue; | ||
| } | ||
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| // We have a value for this field but it's an array or an object | ||
| var type = XContentDataHelper.decodeType(nameValue.value()); | ||
| assert type.isPresent(); | ||
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| try ( | ||
| XContentParser parser = type.get() | ||
| .xContent() | ||
| .createParser( | ||
| XContentParserConfiguration.EMPTY, | ||
| nameValue.value().bytes, | ||
| nameValue.value().offset + 1, | ||
| nameValue.value().length - 1 | ||
| ) | ||
| ) { | ||
| parser.nextToken(); | ||
| reader.parse(parser, blockValues); | ||
| } | ||
| } | ||
| } | ||
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| private void readFromParentValue( | ||
| Map<String, List<IgnoredSourceFieldMapper.NameValue>> valuesForFieldAndParents, | ||
| List<T> blockValues | ||
| ) throws IOException { | ||
| if (valuesForFieldAndParents.isEmpty()) { | ||
| return; | ||
| } | ||
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| // If a parent object is stored at a particular level its children won't be stored. | ||
| // So we should only ever have one parent here. | ||
| assert valuesForFieldAndParents.size() == 1 : "_ignored_source field contains multiple levels of the same object"; | ||
| var parentValues = valuesForFieldAndParents.values().iterator().next(); | ||
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| for (var nameValue : parentValues) { | ||
| parseFieldFromParent(nameValue, blockValues); | ||
| } | ||
| } | ||
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| private void parseFieldFromParent(IgnoredSourceFieldMapper.NameValue nameValue, List<T> blockValues) throws IOException { | ||
|
There was a problem hiding this comment. So this stuff is pretty similar to existing logic in |
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| var type = XContentDataHelper.decodeType(nameValue.value()); | ||
| assert type.isPresent(); | ||
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| String nameAtThisLevel = fieldName.substring(nameValue.name().length() + 1); | ||
| var filterParserConfig = XContentParserConfiguration.EMPTY.withFiltering(null, Set.of(nameAtThisLevel), Set.of(), true); | ||
| try ( | ||
| XContentParser parser = type.get() | ||
| .xContent() | ||
| .createParser(filterParserConfig, nameValue.value().bytes, nameValue.value().offset + 1, nameValue.value().length - 1) | ||
| ) { | ||
| parser.nextToken(); | ||
| var fieldNameInParser = new StringBuilder(nameValue.name()); | ||
| while (true) { | ||
| if (parser.currentToken() == XContentParser.Token.FIELD_NAME) { | ||
| fieldNameInParser.append('.').append(parser.currentName()); | ||
| if (fieldNameInParser.toString().equals(fieldName)) { | ||
| parser.nextToken(); | ||
| break; | ||
| } | ||
| } | ||
| parser.nextToken(); | ||
| } | ||
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| reader.parse(parser, blockValues); | ||
| } | ||
| } | ||
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| @Override | ||
| public boolean canReuse(int startingDocID) { | ||
|
There was a problem hiding this comment. I don't know what to do here. There was a problem hiding this comment. Like |
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| // TODO | ||
| return false; | ||
| } | ||
| } | ||
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| /** | ||
| * Field-specific implementation that converts data stored in _ignored_source field to block loader values. | ||
| * @param <T> | ||
| */ | ||
| public interface Reader<T> { | ||
| /** | ||
| * Converts a raw stored value for this field to a value in a format suitable for block loader and adds it to the provided | ||
| * accumulator. | ||
| * @param value raw decoded value from _ignored_source field (synthetic _source value) | ||
| * @param accumulator list containing the result of conversion | ||
| */ | ||
| void convertValue(Object value, List<T> accumulator); | ||
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| /** | ||
| * Parses one or more complex values using a provided parser and adds them to the provided accumulator. | ||
| * @param parser parser of a value from _ignored_source field (synthetic _source value) | ||
| * @param accumulator list containing the results of parsing | ||
| */ | ||
| void parse(XContentParser parser, List<T> accumulator) throws IOException; | ||
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| void writeToBlock(List<T> values, Builder blockBuilder); | ||
| } | ||
| } | ||
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I'm still trying to understand if this is necessary. #113827 introduced filtering in source construction. If we set
SourceFilterinSourceLoader.Syntheticinitialization to filter for the requested fields only, do we get a more generic solution that covers all uses of synthetic source? I assume the latter is used inSourceBlockLoader.There was a problem hiding this comment.
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I had a conversation with @martijnvg about this. There is a more general problem here.
SourceProvider/SourceLoaderinfra we are currently using is designed for_searchandgetuse cases and just doesn't fit into ESQL. See #117792. So this is not solely an optimization but also allows to remove workarounds like #117792.