The test framework is now a Java module. All the classes have been moved from org.apache.lucene.*
to org.apache.lucene.tests.*
to avoid package name conflicts with the core module. If you were using the Lucene test framework, the migration should be fairly automatic (package prefix).
Added interval functions and min-should-match support to StandardQueryParser
. This means that interval function prefixes (fn:
) and the @
character after parentheses will parse differently than before. If you need the exact previous behavior, clone the StandardSyntaxParser
from the previous version of Lucene and create a custom query parser with that parser.
Lucene Core now logs certain warnings and errors using Java Util Logging (JUL). It is therefore recommended to install wrapper libraries with JUL logging handlers to feed the log events into your app's own logging system.
Under normal circumstances Lucene won't log anything, but in the case of a problem users should find the logged information in the usual log files.
Lucene also provides a JavaLoggingInfoStream
implementation that logs IndexWriter
events using JUL.
To feed Lucene's log events into the well-known Log4J system, we refer to the Log4j JDK Logging Adapter in combination with the corresponding system property: java.util.logging.manager=org.apache.logging.log4j.jul.LogManager
.
The Kuromoji and Nori analysis modules had some way to customize the backing dictionaries by passing a path to file or classpath resources using some inconsistently implemented APIs. This was buggy from the beginning, but some users made use of it. Due to move to Java module system, especially the resource lookup on classpath stopped to work correctly. The Lucene team therefore implemented new APIs to create dictionary implementations with custom data files. Unfortunately there were some shortcomings in the 9.1 version, also when using the now deprecated ctors, so users are advised to upgrade to Lucene 9.2 or stay with 9.0.
See LUCENE-10558 for more details and workarounds.
All binary analysis packages (and corresponding Maven artifacts) have been renamed and are now consistent with repository module analysis
. You will need to adjust build dependencies to the new coordinates:
Old Artifact Coordinates | New Artifact Coordinates |
---|---|
org.apache.lucene:lucene-analyzers-common | org.apache.lucene:lucene-analysis-common |
org.apache.lucene:lucene-analyzers-icu | org.apache.lucene:lucene-analysis-icu |
org.apache.lucene:lucene-analyzers-kuromoji | org.apache.lucene:lucene-analysis-kuromoji |
org.apache.lucene:lucene-analyzers-morfologik | org.apache.lucene:lucene-analysis-morfologik |
org.apache.lucene:lucene-analyzers-nori | org.apache.lucene:lucene-analysis-nori |
org.apache.lucene:lucene-analyzers-opennlp | org.apache.lucene:lucene-analysis-opennlp |
org.apache.lucene:lucene-analyzers-phonetic | org.apache.lucene:lucene-analysis-phonetic |
org.apache.lucene:lucene-analyzers-smartcn | org.apache.lucene:lucene-analysis-smartcn |
org.apache.lucene:lucene-analyzers-stempel | org.apache.lucene:lucene-analysis-stempel |
LucenePackage
class has been removed. The implementation string can be retrieved from Version.getPackageImplementationVersion()
.
DataOutput
's writeShort()
, writeInt()
, and writeLong()
methods now encode with little-endian byte order. If you have custom subclasses of DataInput
/DataOutput
, you will need to adjust them from big-endian byte order to little-endian byte order.
Java 11 supports to use Direct IO without native wrappers from Java code. NativeUnixDirectory
in the misc module was therefore removed and replaced by DirectIODirectory
. To use it, you need a JVM and operating system that supports Direct IO.
The discountOverlaps()
parameter for both BM25Similarity
and LegacyBM25Similarity
is now set by the constructor of those classes.
These packages in the lucene-misc
module are renamed:
Old Package Name | New Package Name |
---|---|
org.apache.lucene.document | org.apache.lucene.misc.document |
org.apache.lucene.index | org.apache.lucene.misc.index |
org.apache.lucene.search | org.apache.lucene.misc.search |
org.apache.lucene.store | org.apache.lucene.misc.store |
org.apache.lucene.util | org.apache.lucene.misc.util |
The following classes were moved to the lucene-core
module:
These packages in the lucene-sandbox
module are renamed:
Old Package Name | New Package Name |
---|---|
org.apache.lucene.codecs | org.apache.lucene.sandbox.codecs |
org.apache.lucene.document | org.apache.lucene.sandbox.document |
org.apache.lucene.search | org.apache.lucene.sandbox.search |
These packages in the lucene-backwards-codecs
module are renamed:
Old Package Name | New Package Name |
---|---|
org.apache.lucene.codecs | org.apache.lucene.backward_codecs |
Previously, JapanesePartOfSpeechStopFilterFactory
added no filter if args
didn't include "tags". Now, it will load the default stop tags returned by JapaneseAnalyzer.getDefaultStopTags()
(i.e. the tags fromstoptags.txt
in the lucene-analyzers-kuromoji
jar.)
These packages in the lucene-analysis-icu
module are renamed:
Old Package Name | New Package Name |
---|---|
org.apache.lucene.collation | org.apache.lucene.analysis.icu |
Base analysis factories are moved to lucene-core
, also their package names are renamed.
Old Class Name | New Class Name |
---|---|
org.apache.lucene.analysis.util.TokenizerFactory | org.apache.lucene.analysis.TokenizerFactory |
org.apache.lucene.analysis.util.CharFilterFactory | org.apache.lucene.analysis.CharFilterFactory |
org.apache.lucene.analysis.util.TokenFilterFactory | org.apache.lucene.analysis.TokenizerFactory |
The service provider files placed in META-INF/services
for custom analysis factories should be renamed as follows:
StandardTokenizerFactory
is moved to lucene-core
module.
The org.apache.lucene.analysis.standard
package in lucene-analysis-common
module is split into org.apache.lucene.analysis.classic
and org.apache.lucene.analysis.email
.
We now follow the Java rules for accepting backslashes. Alphabetic characters other than s, S, w, W, d or D that are preceded by a backslash are considered illegal syntax and will throw an exception.
The commonly used regular expressions \w \W \d \D \s and \S now work the same way Java Pattern matching works. Previously these expressions were (mis)interpreted as searches for the literal characters w, d, s etc.
The factory option name to output the original term was corrected in accordance with its Javadoc.
This command-line tool no longer forceMerges to a single segment. Instead, by default it just follows (configurable) merge policy. If you really want to merge to a single segment, you can pass -max-segments 1
.
Simply use FSTCompiler
instead of the previous Builder
. Use either the simple constructor with default settings, or the FSTCompiler.Builder
to tune and tweak any parameter.
User dictionary now strictly validates if the (concatenated) segment is the same as the surface form. This change avoids unexpected runtime exceptions or behaviours. For example, these entries are not allowed at all and an exception is thrown when loading the dictionary file.
# concatenated "日本経済新聞" does not match the surface form "日経新聞"
日経新聞,日本 経済 新聞,ニホン ケイザイ シンブン,カスタム名詞
# concatenated "日経新聞" does not match the surface form "日本経済新聞"
日本経済新聞,日経 新聞,ニッケイ シンブン,カスタム名詞
JapaneseTokenizer
and JapaneseAnalyzer
no longer emits original tokens when discardCompoundToken
option is not specified. The constructor option has been introduced since Lucene 8.5.0, and the default value is changed to true
.
When given the text "株式会社", JapaneseTokenizer (mode != NORMAL) emits decompounded tokens "株式" and "会社" only and no longer outputs the original token "株式会社" by default. To output original tokens, discardCompoundToken
option should be explicitly set to false
. Be aware that if this option is set to false
, SynonymFilter
or SynonymGraphFilter
does not work correctly (see LUCENE-9173).
The SPI names for concrete subclasses of TokenizerFactory
, TokenFilterFactory
, and CharfilterFactory
are no longer derived from their class name. Instead, each factory must have a static "NAME" field like this:
/** o.a.l.a.standard.StandardTokenizerFactory's SPI name */
public static final String NAME = "standard";
A factory can be resolved/instantiated with its NAME
by using methods such as TokenizerFactory.lookupClass(String)
or TokenizerFactory.forName(String, Map<String,String>)
.
If there are any user-defined factory classes that don't have proper NAME
field, an exception will be thrown when (re)loading factories. e.g., when calling TokenizerFactory.reloadTokenizers(ClassLoader)
.
In addition starting all factories need to implement a public no-arg constructor, too. The reason for this change comes from the fact that Lucene now uses java.util.ServiceLoader
instead its own implementation to load the factory classes to be compatible with Java Module System changes (e.g., load factories from modules). In the future, extensions to Lucene developed on the Java Module System may expose the factories from their module-info.java
file instead of META-INF/services
.
This constructor is never called by Lucene, so by default it throws an UnsupportedOperationException
. User-defined factory classes should implement it in the following way:
/** Default ctor for compatibility with SPI */
public StandardTokenizerFactory() {
throw defaultCtorException();
}
(defaultCtorException()
is a protected static helper method)
TermsEnum
has been changed to be fully abstract, so non-abstract subclasses must implement all its methods. Non-Performance critical TermsEnum
s can use BaseTermsEnum
as a base class instead. The change was motivated by several performance issues with FilterTermsEnum
that caused significant slowdowns and massive memory consumption due to not delegating all method from TermsEnum
.
RAM-based directory implementation have been removed. ByteBuffersDirectory
can be used as a RAM-resident replacement, although it is discouraged in favor of the default MMapDirectory
.
SpanQuery
and PhraseQuery
now always calculate their slops as (1.0 / (1.0 + distance))
. Payload factor calculation is performed by PayloadDecoder
in the lucene-queries
module.
Scorer
s are no longer allowed to produce negative scores. If you have custom query implementations, you should make sure their score formula may never produce negative scores.
As a side-effect of this change, negative boosts are now rejected and FunctionScoreQuery
maps negative values to 0.
Instead use FunctionScoreQuery
and a DoubleValuesSource
implementation. BoostedQuery
and BoostingQuery
may be replaced by calls to FunctionScoreQuery.boostByValue()
and FunctionScoreQuery.boostByQuery()
. To replace more complex calculations in CustomScoreQuery
, use the lucene-expressions
module:
SimpleBindings bindings = new SimpleBindings();
bindings.add("score", DoubleValuesSource.SCORES);
bindings.add("boost1", DoubleValuesSource.fromIntField("myboostfield"));
bindings.add("boost2", DoubleValuesSource.fromIntField("myotherboostfield"));
Expression expr = JavascriptCompiler.compile("score * (boost1 + ln(boost2))");
FunctionScoreQuery q = new FunctionScoreQuery(inputQuery, expr.getDoubleValuesSource(bindings));
Changing IndexOptions
for a field on the fly will now result into an IllegalArgumentException
. If a field is indexed (FieldType.indexOptions() != IndexOptions.NONE
) then all documents must have the same index options for that field.
Instead use IndexSearcher.createWeight()
, rewriting the query first, and using a boost of 1f
.
Memory codecs (MemoryPostingsFormat
, MemoryDocValuesFormat
) have been removed from the codebase.
The Direct
doc-value format has been removed from the codebase.
Caching everything is discouraged as it disables the ability to skip non-interesting documents. ALWAYS_CACHE
can be replaced by a UsageTrackingQueryCachingPolicy
with an appropriate config.
To retain the old behaviour, pass EnglishAnalyzer.ENGLISH_STOP_WORDS_SET
as an argument to the constructor
English stop words are now defined in EnglishAnalyzer.ENGLISH_STOP_WORDS_SET
in the analysis-common
module.
TopDocs.maxScore
is removed. IndexSearcher
and TopFieldCollector
no longer have an option to compute the maximum score when sorting by field. If you need to know the maximum score for a query, the recommended approach is to run a separate query:
TopDocs topHits = searcher.search(query, 1);
float maxScore = topHits.scoreDocs.length == 0 ? Float.NaN : topHits.scoreDocs[0].score;
Thanks to other optimizations that were added to Lucene 8, this query will be able to efficiently select the top-scoring document without having to visit all matches.
Because filling sort values doesn't have a significant overhead, the fillFields
option has been removed from TopFieldCollector
factory methods. Everything behaves as if it was previously set to true
.
Computing scores at collection time is less efficient than running a second request in order to only compute scores for documents that made it to the top hits. As a consequence, the trackDocScores
option has been removed and can be replaced with the new TopFieldCollector.populateScores()
helper method.
Lucene 8 received optimizations for collection of top-k matches by not visiting all matches. However these optimizations won't help if all matches still need to be visited in order to compute the total number of hits. As a consequence, IndexSearcher
's search()
and searchAfter()
methods were changed to only count hits accurately up to 1,000, and Topdocs.totalHits
was changed from a long
to an object that says whether the hit count is accurate or a lower bound of the actual hit count.
This RAM-based directory implementation is an old piece of code that uses inefficient thread synchronization primitives and can be confused as "faster" than the NIO-based MMapDirectory
. It is deprecated and scheduled for removal in future versions of Lucene.
Scorer
has a number of methods that should never be called from Collector
s, for example those that advance the underlying iterators. To hide these, LeafCollector.setScorer()
now takes a Scorable
, an abstract class that scorers can extend, with methods docId()
and score()
.
If a custom Scorer
implementation does not have an associated Weight
, it can probably be replaced with a Scorable
instead.
Most code should just require recompilation, though possibly requiring some added casts.
Instead of overriding TokenStreamComponents.setReader()
to customise analyzer initialisation, you should now pass a Consumer<Reader>
instance to the TokenStreamComponents
constructor.
LowerCaseTokenizer
combined tokenization and filtering in a way that broke token normalization, so they have been removed. Instead, use a LetterTokenizer
followed by a LowerCaseFilter
.
CharTokenizer
now only performs tokenization. To perform any type of filtering use a TokenFilter
chain as you would with any other Tokenizer
.
Both Highlighter
and FastVectorHighlighter
need a custom WeightedSpanTermExtractor
or FieldQuery
, respectively, in order to support ToParentBlockJoinQuery
/ToChildBlockJoinQuery
.
Normalization is now type-safe, with CharFilterFactory.normalize()
returning a Reader
and TokenFilterFactory.normalize()
returning a TokenFilter
.
Scores computed by the BM25Similarity
are lower than previously as the k1+1
constant factor was removed from the numerator of the scoring formula. Ordering of results is preserved unless scores are computed from multiple fields using different similarities. The previous behaviour is now exposed by the LegacyBM25Similarity
class which can be found in the lucene-misc jar.
IndexWriter.getDocStats()
should be used instead of maxDoc()
/ numDocs()
which offers a consistent view on document stats. Previously calling two methods in order to get point in time stats was subject to concurrent changes.
IndexSearcher
now performs max clause count checks on all types of queries (including BooleanQueries). This led to a logical move of the clauses count from BooleanQuery
to IndexSearcher
.
TopDocs.merge()
's API has been changed to stop allowing passing in a parameter to indicate if it should set shard indices for hits as they are seen during the merge process. This is done to simplify the API to be more dynamic in terms of passing in custom tie breakers. If shard indices are to be used for tie breaking docs with equal scores during TopDocs.merge()
, then it is mandatory that the input ScoreDocs
have their shard indices set to valid values prior to calling merge()
TopDocsCollector
shall no longer return an empty TopDocs
for malformed arguments. Rather, an IllegalArgumentException
shall be thrown. This is introduced for better defence and to ensure that there is no bubbling up of errors when Lucene is used in multi level applications
Sorting on a numeric field that is indexed with both doc values and points may use an optimization to skip non-competitive documents. This optimization relies on the assumption that the same data is stored in these points and doc values.
The per field data-structures are implicitly defined by the first document indexed that contains a certain field. Once defined, the per field data-structures are not changeable for the whole index. For example, if you first index a document where a certain field is indexed with doc values and points, all subsequent documents containing this field must also have this field indexed with only doc values and points.
This also means that an index created in the previous version that doesn't satisfy this requirement can not be updated.
Previously IndexWriter could update doc values for a binary or numeric docValue field that was also indexed with other data structures (e.g. postings, vectors etc). This is not allowed anymore. A field must be indexed with only doc values to be allowed for doc values updates in IndexWriter
.
SortedDocValues
no longer extends BinaryDocValues
: SortedDocValues
do not have a per-document binary value, they have a per-document numeric ordValue()
. The ordinal can then be dereferenced to its binary form with lookupOrd()
, but it was a performance trap to implement a binaryValue()
on the SortedDocValues api that does this behind-the-scenes on every document.
You can replace calls of binaryValue()
with lookupOrd(ordValue())
as a "quick fix", but it is better to use the ordinal alone (integer-based datastructures) for per-document access, and only call lookupOrd()
a few times at the end (e.g. for the hits you want to display). Otherwise, if you really don't want per-document ordinals, but instead a per-document byte[]
, use a BinaryDocValues
field.
Lucene index readers are now using so little memory with the default codec that it was decided to remove the ability to estimate their RAM usage.
LongValueFacetCounts
will now automatically detect whether-or-not an indexed field is single- or multi-valued. The user no longer needs to provide this information to the ctors. Migrating should be as simple as no longer providing this boolean.
They can now be found in the org.apache.lucene.queries.spans
package.
SpanBoostQuery
was a no-op unless used at the top level of a SpanQuery
nested structure. Use a standard BoostQuery
here instead.
Rather than using setSort()
to change sort values, you should instead create a new Sort
instance with the new values.
The side-car taxonomy index now uses doc values for ord-to-path lookup (LUCENE-9450) and parent lookup (LUCENE-10122) instead of stored fields and positions (respectively). Document ordinals are now encoded with SortedNumericDocValues
instead of using a custom (v-int) binary format. Performance gains have been observed with these encoding changes, but to benefit from them, users must create a new index using 9.x (it is not sufficient to reindex documents against an existing 8.x index). In order to remain backwards-compatible with 8.x indexes, the older format is retained until a full rebuild is done.
Additionally, OrdinalsReader
(and sub-classes) have been marked @Deprecated
as custom binary encodings will not be supported for Document ordinals in 9.x onwards (SortedNumericDocValues
are used out-of-the-box instead).