org.elasticsearch.search.fetch.subphase.highlight.HighlightPhase Maven / Gradle / Ivy

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 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
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 * ownership. Elasticsearch 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,
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package org.elasticsearch.search.fetch.subphase.highlight;

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.Query;
import org.elasticsearch.common.regex.Regex;
import org.elasticsearch.index.mapper.KeywordFieldMapper;
import org.elasticsearch.index.mapper.MappedFieldType;
import org.elasticsearch.index.mapper.SourceFieldMapper;
import org.elasticsearch.index.mapper.TextFieldMapper;
import org.elasticsearch.search.fetch.FetchContext;
import org.elasticsearch.search.fetch.FetchSubPhase;
import org.elasticsearch.search.fetch.FetchSubPhaseProcessor;

import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.function.Function;

public class HighlightPhase implements FetchSubPhase {

    private final Map highlighters;

    public HighlightPhase(Map highlighters) {
        this.highlighters = highlighters;
    }

    @Override
    public FetchSubPhaseProcessor getProcessor(FetchContext context) {
        if (context.highlight() == null) {
            return null;
        }

        return getProcessor(context, context.highlight(), context.parsedQuery().query());
    }

    public FetchSubPhaseProcessor getProcessor(FetchContext context, SearchHighlightContext highlightContext, Query query) {
        Map> contextBuilders = contextBuilders(context, highlightContext, query);
        return new FetchSubPhaseProcessor() {
            @Override
            public void setNextReader(LeafReaderContext readerContext) {

            }

            @Override
            public void process(HitContext hitContext) throws IOException {
                Map highlightFields = new HashMap<>();
                for (String field : contextBuilders.keySet()) {
                    FieldHighlightContext fieldContext = contextBuilders.get(field).apply(hitContext);
                    Highlighter highlighter = getHighlighter(fieldContext.field);
                    HighlightField highlightField = highlighter.highlight(fieldContext);
                    if (highlightField != null) {
                        // Note that we make sure to use the original field name in the response. This is because the
                        // original field could be an alias, and highlighter implementations may instead reference the
                        // concrete field it points to.
                        highlightFields.put(field,
                            new HighlightField(field, highlightField.fragments()));
                    }
                }
                hitContext.hit().highlightFields(highlightFields);
            }
        };
    }

    private Highlighter getHighlighter(SearchHighlightContext.Field field) {
        String highlighterType = field.fieldOptions().highlighterType();
        if (highlighterType == null) {
            highlighterType = "unified";
        }
        Highlighter highlighter = highlighters.get(highlighterType);
        if (highlighter == null) {
            throw new IllegalArgumentException("unknown highlighter type [" + highlighterType
                + "] for the field [" + field.field() + "]");
        }
        return highlighter;
    }

    private Map> contextBuilders(FetchContext context,
                                                                                     SearchHighlightContext highlightContext,
                                                                                     Query query) {
        Map> builders = new LinkedHashMap<>();
        for (SearchHighlightContext.Field field : highlightContext.fields()) {
            Highlighter highlighter = getHighlighter(field);
            Collection fieldNamesToHighlight;
            if (Regex.isSimpleMatchPattern(field.field())) {
                fieldNamesToHighlight = context.mapperService().simpleMatchToFullName(field.field());
            } else {
                fieldNamesToHighlight = Collections.singletonList(field.field());
            }

            if (highlightContext.forceSource(field)) {
                SourceFieldMapper sourceFieldMapper = context.mapperService().documentMapper().sourceMapper();
                if (sourceFieldMapper.enabled() == false) {
                    throw new IllegalArgumentException("source is forced for fields " + fieldNamesToHighlight
                        + " but _source is disabled");
                }
            }

            boolean fieldNameContainsWildcards = field.field().contains("*");
            for (String fieldName : fieldNamesToHighlight) {
                MappedFieldType fieldType = context.mapperService().fieldType(fieldName);
                if (fieldType == null) {
                    continue;
                }

                // We should prevent highlighting if a field is anything but a text or keyword field.
                // However, someone might implement a custom field type that has text and still want to
                // highlight on that. We cannot know in advance if the highlighter will be able to
                // highlight such a field and so we do the following:
                // If the field is only highlighted because the field matches a wildcard we assume
                // it was a mistake and do not process it.
                // If the field was explicitly given we assume that whoever issued the query knew
                // what they were doing and try to highlight anyway.
                if (fieldNameContainsWildcards) {
                    if (fieldType.typeName().equals(TextFieldMapper.CONTENT_TYPE) == false &&
                        fieldType.typeName().equals(KeywordFieldMapper.CONTENT_TYPE) == false) {
                        continue;
                    }
                    if (highlighter.canHighlight(fieldType) == false) {
                        continue;
                    }
                }

                Query highlightQuery = field.fieldOptions().highlightQuery();

                boolean forceSource = highlightContext.forceSource(field);
                builders.put(fieldName,
                    hc -> new FieldHighlightContext(fieldType.name(), field, fieldType, context, hc,
                        highlightQuery == null ? query : highlightQuery, forceSource));
            }
        }
        return builders;
    }
}