/*
* 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.lucene.codecs;
import org.apache.lucene.codecs.blocktree.BlockTreeTermsWriter;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.SegmentWriteState;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.store.DataOutput;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.FixedBitSet;
import java.io.Closeable;
import java.io.IOException;
/**
* Class that plugs into term dictionaries, such as {@link
* BlockTreeTermsWriter}, and handles writing postings.
*
* @see PostingsReaderBase
* @lucene.experimental
*/
// TODO: find a better name; this defines the API that the
// terms dict impls use to talk to a postings impl.
// TermsDict + PostingsReader/WriterBase == FieldsProducer/Consumer
public abstract class PostingsWriterBase implements Closeable {
/** Sole constructor. (For invocation by subclass
* constructors, typically implicit.) */
protected PostingsWriterBase() {
}
/** Called once after startup, before any terms have been
* added. Implementations typically write a header to
* the provided {@code termsOut}. */
public abstract void init(IndexOutput termsOut, SegmentWriteState state) throws IOException;
/** Write all postings for one term; use the provided
* {@link TermsEnum} to pull a {@link org.apache.lucene.index.PostingsEnum}.
* This method should not
* re-position the {@code TermsEnum}! It is already
* positioned on the term that should be written. This
* method must set the bit in the provided {@link
* FixedBitSet} for every docID written. If no docs
* were written, this method should return null, and the
* terms dict will skip the term. */
public abstract BlockTermState writeTerm(BytesRef term, TermsEnum termsEnum, FixedBitSet docsSeen) throws IOException;
/**
* Encode metadata as long[] and byte[]. {@code absolute} controls whether
* current term is delta encoded according to latest term.
* Usually elements in {@code longs} are file pointers, so each one always
* increases when a new term is consumed. {@code out} is used to write generic
* bytes, which are not monotonic.
*
* NOTE: sometimes long[] might contain "don't care" values that are unused, e.g.
* the pointer to postings list may not be defined for some terms but is defined
* for others, if it is designed to inline some postings data in term dictionary.
* In this case, the postings writer should always use the last value, so that each
* element in metadata long[] remains monotonic.
*/
public abstract void encodeTerm(long[] longs, DataOutput out, FieldInfo fieldInfo, BlockTermState state, boolean absolute) throws IOException;
/**
* Sets the current field for writing, and returns the
* fixed length of long[] metadata (which is fixed per
* field), called when the writing switches to another field. */
// TODO: better name?
public abstract int setField(FieldInfo fieldInfo);
@Override
public abstract void close() throws IOException;
}