public final class Lucene42DocValuesFormat extends DocValuesFormat
Encodes the four per-document value types (Numeric,Binary,Sorted,SortedSet) with seven basic strategies.
acceptableOverheadRatiowould pack values into 8 bits per value anyway, they are written as absolute values (with no indirection or packing) for performance.
The DocValues metadata or .dvm file.
For DocValues field, this stores metadata, such as the offset into the DocValues data (.dvd)
DocValues metadata (.dvm) --> Header,<FieldNumber,EntryType,Entry>NumFields
Sorted fields have two entries: a SortedEntry with the FST metadata, and an ordinary NumericEntry for the document-to-ord metadata.
SortedSet fields have two entries: a SortedEntry with the FST metadata, and an ordinary BinaryEntry for the document-to-ord-list metadata.
FieldNumber of -1 indicates the end of metadata.
EntryType is a 0 (NumericEntry), 1 (BinaryEntry, or 2 (SortedEntry)
DataOffset is the pointer to the start of the data in the DocValues data (.dvd)
CompressionType indicates how Numeric values will be compressed:
acceptableOverheadRatioparameter would upgrade the number of bits required to 8, and all values fit in a byte, these are written as absolute binary values for performance.
MinLength and MaxLength represent the min and max byte value lengths for Binary values. If they are equal, then all values are of a fixed size, and can be addressed as DataOffset + (docID * length). Otherwise, the binary values are of variable size, and packed integer metadata (PackedVersion,BlockSize) is written for the addresses.
The DocValues data or .dvd file.
For DocValues field, this stores the actual per-document data (the heavy-lifting)
DocValues data (.dvd) --> Header,<NumericData | BinaryData | SortedData>NumFields
SortedSet entries store the list of ordinals in their BinaryData as a
sequences of increasing
|Constructor and Description|
|Modifier and Type||Method and Description|
availableDocValuesFormats, forName, getName, reloadDocValuesFormats, toString
public DocValuesConsumer fieldsConsumer(SegmentWriteState state) throws IOException
DocValuesConsumerto write docvalues to the index.
public DocValuesProducer fieldsProducer(SegmentReadState state) throws IOException
DocValuesProducerto read docvalues from the index.
NOTE: by the time this call returns, it must hold open any files it will need to use; else, those files may be deleted. Additionally, required files may be deleted during the execution of this call before there is a chance to open them. Under these circumstances an IOException should be thrown by the implementation. IOExceptions are expected and will automatically cause a retry of the segment opening logic with the newly revised segments.
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