Class DocValuesTermsQuery
- All Implemented Interfaces:
Accountable
Query
that only accepts documents whose term value in the specified field is contained
in the provided set of allowed terms.
This is the same functionality as TermsQuery (from queries/), but because of drastically different implementations, they also have different performance characteristics, as described below.
NOTE: be very careful using this query: it is typically much slower than using
TermsQuery
, but in certain specialized cases may be faster.
With each search, this query translates the specified set of Terms into a private LongBitSet
keyed by term number per unique IndexReader
(normally one reader per
segment). Then, during matching, the term number for each docID is retrieved from the cache and
then checked for inclusion using the LongBitSet
. Since all testing is done using RAM
resident data structures, performance should be very fast, most likely fast enough to not require
further caching of the DocIdSet for each possible combination of terms. However, because docIDs
are simply scanned linearly, an index with a great many small documents may find this linear scan
too costly.
In contrast, TermsQuery builds up an FixedBitSet
, keyed by docID, every time it's
created, by enumerating through all matching docs using PostingsEnum
to seek and scan through each term's docID list. While
there is no linear scan of all docIDs, besides the allocation of the underlying array in the
FixedBitSet
, this approach requires a number of "disk seeks" in proportion to the number
of terms, which can be exceptionally costly when there are cache misses in the OS's IO cache.
Generally, this filter will be slower on the first invocation for a given field, but subsequent invocations, even if you change the allowed set of Terms, should be faster than TermsQuery, especially as the number of Terms being matched increases. If you are matching only a very small number of terms, and those terms in turn match a very small number of documents, TermsQuery may perform faster.
Which query is best is very application dependent.
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate static final long
private final String
private final PrefixCodedTerms
private final int
Fields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE
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Constructor Summary
ConstructorsConstructorDescriptionDocValuesTermsQuery
(String field, String... terms) DocValuesTermsQuery
(String field, Collection<BytesRef> terms) DocValuesTermsQuery
(String field, BytesRef... terms) -
Method Summary
Modifier and TypeMethodDescriptioncreateWeight
(IndexSearcher searcher, ScoreMode scoreMode, float boost) Expert: Constructs an appropriate Weight implementation for this query.boolean
Override and implement query instance equivalence properly in a subclass.private boolean
equalsTo
(DocValuesTermsQuery other) getField()
getTerms()
int
hashCode()
Override and implement query hash code properly in a subclass.long
Return the memory usage of this object in bytes.Prints a query to a string, withfield
assumed to be the default field and omitted.void
visit
(QueryVisitor visitor) Recurse through the query tree, visiting any child queriesMethods inherited from class org.apache.lucene.search.Query
classHash, rewrite, sameClassAs, toString
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface org.apache.lucene.util.Accountable
getChildResources
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Field Details
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BASE_RAM_BYTES
private static final long BASE_RAM_BYTES -
field
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termData
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termDataHashCode
private final int termDataHashCode
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Constructor Details
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DocValuesTermsQuery
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DocValuesTermsQuery
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DocValuesTermsQuery
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Method Details
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equals
Description copied from class:Query
Override and implement query instance equivalence properly in a subclass. This is required so thatQueryCache
works properly.Typically a query will be equal to another only if it's an instance of the same class and its document-filtering properties are identical that other instance. Utility methods are provided for certain repetitive code.
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equalsTo
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hashCode
public int hashCode()Description copied from class:Query
Override and implement query hash code properly in a subclass. This is required so thatQueryCache
works properly. -
toString
Description copied from class:Query
Prints a query to a string, withfield
assumed to be the default field and omitted. -
getField
- Returns:
- the name of the field searched by this query.
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getTerms
- Returns:
- the terms looked up by this query, prefix-encoded.
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ramBytesUsed
public long ramBytesUsed()Description copied from interface:Accountable
Return the memory usage of this object in bytes. Negative values are illegal.- Specified by:
ramBytesUsed
in interfaceAccountable
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visit
Description copied from class:Query
Recurse through the query tree, visiting any child queries -
createWeight
public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws IOException Description copied from class:Query
Expert: Constructs an appropriate Weight implementation for this query.Only implemented by primitive queries, which re-write to themselves.
- Overrides:
createWeight
in classQuery
scoreMode
- How the produced scorers will be consumed.boost
- The boost that is propagated by the parent queries.- Throws:
IOException
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