Class Lucene90BlockTreeTermsWriter
- All Implemented Interfaces:
Closeable,AutoCloseable
Writes terms dict and index, block-encoding (column stride) each term's metadata for each set of terms between two index terms.
Files:
.tim: Term Dictionary.tmd: Term Metadata.tip: Term Index
Term Dictionary
The .tim file contains the list of terms in each field along with per-term statistics (such as docfreq) and per-term metadata (typically pointers to the postings list for that term in the inverted index).
The .tim is arranged in blocks: with blocks containing a variable number of entries (by default 25-48), where each entry is either a term or a reference to a sub-block.
NOTE: The term dictionary can plug into different postings implementations: the postings writer/reader are actually responsible for encoding and decoding the Postings Metadata and Term Metadata sections.
- TermsDict (.tim) --> Header, FieldDictNumFields, Footer
- FieldDict --> PostingsHeader, NodeBlockNumBlocks
- NodeBlock --> (OuterNode | InnerNode)
- OuterNode --> EntryCount, SuffixLength, ByteSuffixLength, StatsLength, < TermStats >EntryCount, MetaLength, <TermMetadata>EntryCount
- InnerNode --> EntryCount, SuffixLength[,Sub?], ByteSuffixLength, StatsLength, < TermStats ? >EntryCount, MetaLength, <TermMetadata ? >EntryCount
- TermStats --> DocFreq, TotalTermFreq
- Header -->
CodecHeader - EntryCount,SuffixLength,StatsLength,DocFreq,MetaLength -->
VInt - TotalTermFreq -->
VLong - Footer -->
CodecFooter
Notes:
- Header is a
CodecHeaderstoring the version information for the BlockTree implementation. - DocFreq is the count of documents which contain the term.
- TotalTermFreq is the total number of occurrences of the term. This is encoded as the difference between the total number of occurrences and the DocFreq.
- PostingsHeader and TermMetadata are plugged into by the specific postings implementation: these contain arbitrary per-file data (such as parameters or versioning information) and per-term data (such as pointers to inverted files).
- For inner nodes of the tree, every entry will steal one bit to mark whether it points to child nodes(sub-block). If so, the corresponding TermStats and TermMetaData are omitted.
Term Metadata
The .tmd file contains the list of term metadata (such as FST index metadata) and field level statistics (such as sum of total term freq).
- TermsMeta (.tmd) --> Header, NumFields, <FieldStats>NumFields, TermIndexLength, TermDictLength, Footer
- FieldStats --> FieldNumber, NumTerms, RootCodeLength, ByteRootCodeLength, SumTotalTermFreq?, SumDocFreq, DocCount, MinTerm, MaxTerm, IndexStartFP, FSTHeader, FSTMetadata
- Header,FSTHeader -->
CodecHeader - TermIndexLength, TermDictLength -->
Uint64 - MinTerm,MaxTerm -->
VIntlength followed by the byte[] - NumFields,FieldNumber,RootCodeLength,DocCount -->
VInt - NumTerms,SumTotalTermFreq,SumDocFreq,IndexStartFP -->
VLong - Footer -->
CodecFooter
Notes:
- FieldNumber is the fields number from
FieldInfos. (.fnm) - NumTerms is the number of unique terms for the field.
- RootCode points to the root block for the field.
- SumDocFreq is the total number of postings, the number of term-document pairs across the entire field.
- DocCount is the number of documents that have at least one posting for this field.
- MinTerm, MaxTerm are the lowest and highest term in this field.
Term Index
The .tip file contains an index into the term dictionary, so that it can be accessed randomly. The index is also used to determine when a given term cannot exist on disk (in the .tim file), saving a disk seek.
- TermsIndex (.tip) --> Header, FSTIndexNumFieldsFooter
- Header -->
CodecHeader - FSTIndex -->
FST<byte[]> - Footer -->
CodecFooter
Notes:
- The .tip file contains a separate FST for each field. The FST maps a term prefix to the on-disk block that holds all terms starting with that prefix. Each field's IndexStartFP points to its FST.
- It's possible that an on-disk block would contain too many terms (more than the allowed maximum (default: 48)). When this happens, the block is sub-divided into new blocks (called "floor blocks"), and then the output in the FST for the block's prefix encodes the leading byte of each sub-block, and its file pointer.
- See Also:
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final intSuggested default value for themaxItemsInBlockparameter toLucene90BlockTreeTermsWriter(SegmentWriteState,PostingsWriterBase,int,int).static final intSuggested default value for theminItemsInBlockparameter toLucene90BlockTreeTermsWriter(SegmentWriteState,PostingsWriterBase,int,int).static final intstatic final intstatic final intstatic final int -
Constructor Summary
ConstructorsConstructorDescriptionLucene90BlockTreeTermsWriter(org.apache.lucene.index.SegmentWriteState state, org.apache.lucene.codecs.PostingsWriterBase postingsWriter, int minItemsInBlock, int maxItemsInBlock) Create a new writer.Lucene90BlockTreeTermsWriter(org.apache.lucene.index.SegmentWriteState state, org.apache.lucene.codecs.PostingsWriterBase postingsWriter, int minItemsInBlock, int maxItemsInBlock, int version) Expert constructor that allows configuring the version, used for bw tests. -
Method Summary
Modifier and TypeMethodDescriptionvoidclose()static voidvalidateSettings(int minItemsInBlock, int maxItemsInBlock) ThrowsIllegalArgumentExceptionif any of these settings is invalid.voidwrite(org.apache.lucene.index.Fields fields, org.apache.lucene.codecs.NormsProducer norms) Methods inherited from class org.apache.lucene.codecs.FieldsConsumer
merge
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Field Details
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DEFAULT_MIN_BLOCK_SIZE
public static final int DEFAULT_MIN_BLOCK_SIZESuggested default value for theminItemsInBlockparameter toLucene90BlockTreeTermsWriter(SegmentWriteState,PostingsWriterBase,int,int).- See Also:
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DEFAULT_MAX_BLOCK_SIZE
public static final int DEFAULT_MAX_BLOCK_SIZESuggested default value for themaxItemsInBlockparameter toLucene90BlockTreeTermsWriter(SegmentWriteState,PostingsWriterBase,int,int).- See Also:
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OUTPUT_FLAGS_NUM_BITS
public static final int OUTPUT_FLAGS_NUM_BITS- See Also:
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OUTPUT_FLAGS_MASK
public static final int OUTPUT_FLAGS_MASK- See Also:
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OUTPUT_FLAG_IS_FLOOR
public static final int OUTPUT_FLAG_IS_FLOOR- See Also:
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OUTPUT_FLAG_HAS_TERMS
public static final int OUTPUT_FLAG_HAS_TERMS- See Also:
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Constructor Details
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Lucene90BlockTreeTermsWriter
public Lucene90BlockTreeTermsWriter(org.apache.lucene.index.SegmentWriteState state, org.apache.lucene.codecs.PostingsWriterBase postingsWriter, int minItemsInBlock, int maxItemsInBlock) throws IOException Create a new writer. The number of items (terms or sub-blocks) per block will aim to be between minItemsPerBlock and maxItemsPerBlock, though in some cases the blocks may be smaller than the min.- Throws:
IOException
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Lucene90BlockTreeTermsWriter
public Lucene90BlockTreeTermsWriter(org.apache.lucene.index.SegmentWriteState state, org.apache.lucene.codecs.PostingsWriterBase postingsWriter, int minItemsInBlock, int maxItemsInBlock, int version) throws IOException Expert constructor that allows configuring the version, used for bw tests.- Throws:
IOException
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Method Details
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validateSettings
public static void validateSettings(int minItemsInBlock, int maxItemsInBlock) ThrowsIllegalArgumentExceptionif any of these settings is invalid. -
write
public void write(org.apache.lucene.index.Fields fields, org.apache.lucene.codecs.NormsProducer norms) throws IOException - Specified by:
writein classorg.apache.lucene.codecs.FieldsConsumer- Throws:
IOException
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close
- Specified by:
closein interfaceAutoCloseable- Specified by:
closein interfaceCloseable- Specified by:
closein classorg.apache.lucene.codecs.FieldsConsumer- Throws:
IOException
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