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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* 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,
* 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.elasticsearch.search.slice;
import org.apache.lucene.search.MatchAllDocsQuery;
import org.apache.lucene.search.MatchNoDocsQuery;
import org.apache.lucene.search.Query;
import org.elasticsearch.common.ParseField;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.common.xcontent.ObjectParser;
import org.elasticsearch.common.xcontent.ToXContentObject;
import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.common.xcontent.XContentParser;
import org.elasticsearch.index.fielddata.IndexFieldData;
import org.elasticsearch.index.fielddata.IndexNumericFieldData;
import org.elasticsearch.index.mapper.IdFieldMapper;
import org.elasticsearch.index.mapper.MappedFieldType;
import org.elasticsearch.index.mapper.UidFieldMapper;
import org.elasticsearch.index.query.QueryShardContext;
import java.io.IOException;
import java.util.Objects;
/**
* A slice builder allowing to split a scroll in multiple partitions.
* If the provided field is the "_uid" it uses a {@link org.elasticsearch.search.slice.TermsSliceQuery}
* to do the slicing. The slicing is done at the shard level first and then each shard is split into multiple slices.
* For instance if the number of shards is equal to 2 and the user requested 4 slices
* then the slices 0 and 2 are assigned to the first shard and the slices 1 and 3 are assigned to the second shard.
* This way the total number of bitsets that we need to build on each shard is bounded by the number of slices
* (instead of {@code numShards*numSlices}).
* Otherwise the provided field must be a numeric and doc_values must be enabled. In that case a
* {@link org.elasticsearch.search.slice.DocValuesSliceQuery} is used to filter the results.
*/
public class SliceBuilder implements Writeable, ToXContentObject {
public static final ParseField FIELD_FIELD = new ParseField("field");
public static final ParseField ID_FIELD = new ParseField("id");
public static final ParseField MAX_FIELD = new ParseField("max");
private static final ObjectParser PARSER =
new ObjectParser<>("slice", SliceBuilder::new);
static {
PARSER.declareString(SliceBuilder::setField, FIELD_FIELD);
PARSER.declareInt(SliceBuilder::setId, ID_FIELD);
PARSER.declareInt(SliceBuilder::setMax, MAX_FIELD);
}
/** Name of field to slice against (_uid by default) */
private String field = UidFieldMapper.NAME;
/** The id of the slice */
private int id = -1;
/** Max number of slices */
private int max = -1;
private SliceBuilder() {}
public SliceBuilder(int id, int max) {
this(UidFieldMapper.NAME, id, max);
}
/**
*
* @param field The name of the field
* @param id The id of the slice
* @param max The maximum number of slices
*/
public SliceBuilder(String field, int id, int max) {
setField(field);
setId(id);
setMax(max);
}
public SliceBuilder(StreamInput in) throws IOException {
this.field = in.readString();
this.id = in.readVInt();
this.max = in.readVInt();
}
@Override
public void writeTo(StreamOutput out) throws IOException {
out.writeString(field);
out.writeVInt(id);
out.writeVInt(max);
}
private SliceBuilder setField(String field) {
if (Strings.isEmpty(field)) {
throw new IllegalArgumentException("field name is null or empty");
}
this.field = field;
return this;
}
/**
* The name of the field to slice against
*/
public String getField() {
return this.field;
}
private SliceBuilder setId(int id) {
if (id < 0) {
throw new IllegalArgumentException("id must be greater than or equal to 0");
}
if (max != -1 && id >= max) {
throw new IllegalArgumentException("max must be greater than id");
}
this.id = id;
return this;
}
/**
* The id of the slice.
*/
public int getId() {
return id;
}
private SliceBuilder setMax(int max) {
if (max <= 1) {
throw new IllegalArgumentException("max must be greater than 1");
}
if (id != -1 && id >= max) {
throw new IllegalArgumentException("max must be greater than id");
}
this.max = max;
return this;
}
/**
* The maximum number of slices.
*/
public int getMax() {
return max;
}
@Override
public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
builder.startObject();
innerToXContent(builder);
builder.endObject();
return builder;
}
void innerToXContent(XContentBuilder builder) throws IOException {
builder.field(FIELD_FIELD.getPreferredName(), field);
builder.field(ID_FIELD.getPreferredName(), id);
builder.field(MAX_FIELD.getPreferredName(), max);
}
public static SliceBuilder fromXContent(XContentParser parser) throws IOException {
SliceBuilder builder = PARSER.parse(parser, new SliceBuilder(), null);
return builder;
}
@Override
public boolean equals(Object other) {
if (!(other instanceof SliceBuilder)) {
return false;
}
SliceBuilder o = (SliceBuilder) other;
return ((field == null && o.field == null) || field.equals(o.field))
&& id == o.id && o.max == max;
}
@Override
public int hashCode() {
return Objects.hash(this.field, this.id, this.max);
}
public Query toFilter(QueryShardContext context, int shardId, int numShards) {
final MappedFieldType type = context.fieldMapper(field);
if (type == null) {
throw new IllegalArgumentException("field " + field + " not found");
}
String field = this.field;
boolean useTermQuery = false;
if (UidFieldMapper.NAME.equals(field)) {
if (context.getIndexSettings().isSingleType()) {
// on new indices, the _id acts as a _uid
field = IdFieldMapper.NAME;
}
useTermQuery = true;
} else if (type.hasDocValues() == false) {
throw new IllegalArgumentException("cannot load numeric doc values on " + field);
} else {
IndexFieldData ifm = context.getForField(type);
if (ifm instanceof IndexNumericFieldData == false) {
throw new IllegalArgumentException("cannot load numeric doc values on " + field);
}
}
if (numShards == 1) {
return useTermQuery ? new TermsSliceQuery(field, id, max) :
new DocValuesSliceQuery(field, id, max);
}
if (max >= numShards) {
// the number of slices is greater than the number of shards
// in such case we can reduce the number of requested shards by slice
// first we check if the slice is responsible of this shard
int targetShard = id % numShards;
if (targetShard != shardId) {
// the shard is not part of this slice, we can skip it.
return new MatchNoDocsQuery("this shard is not part of the slice");
}
// compute the number of slices where this shard appears
int numSlicesInShard = max / numShards;
int rest = max % numShards;
if (rest > targetShard) {
numSlicesInShard++;
}
if (numSlicesInShard == 1) {
// this shard has only one slice so we must check all the documents
return new MatchAllDocsQuery();
}
// get the new slice id for this shard
int shardSlice = id / numShards;
return useTermQuery ?
new TermsSliceQuery(field, shardSlice, numSlicesInShard) :
new DocValuesSliceQuery(field, shardSlice, numSlicesInShard);
}
// the number of shards is greater than the number of slices
// check if the shard is assigned to the slice
int targetSlice = shardId % max;
if (id != targetSlice) {
// the shard is not part of this slice, we can skip it.
return new MatchNoDocsQuery("this shard is not part of the slice");
}
return new MatchAllDocsQuery();
}
@Override
public String toString() {
return Strings.toString(this, true, true);
}
}