java.lang.Object
- it.unimi.di.big.mg4j.index.DiskBasedIndex

```
public class DiskBasedIndex
extends Object
```
A static container providing facilities to load an index based on data stored on disk.
This class contains several useful static methods such as readOffsets(InputBitStream, long), readSizes(CharSequence, long), loadLongBigList(CharSequence, ByteOrder) and static factor methods such as getInstance(CharSequence, boolean, boolean, boolean, EnumMap) that take care of reading the properties associated with the index, identify the correct Index implementation that should be used to load the index, and load the necessary data into memory.
As an option, a disk-based index can be loaded into main memory (key: Index.UriKeys.INMEMORY), or mapped into main memory (key: Index.UriKeys.MAPPED) (the value assigned to the keys is irrelevant).
Note that quasi-succinct indices are memory-mapped by default, and for bitstream indices there is a limit of two gigabytes for in-memory indices.
By default the term-offset list is accessed using a SemiExternalOffsetBigList with a step of DEFAULT_OFFSET_STEP. This behaviour can be changed using the URI key Index.UriKeys.OFFSETSTEP.
Disk-based indices are the workhorse of MG4J. All other indices (clustered, remote, etc.) ultimately rely on disk-based indices to provide results.
Note that not all data produced by Scan and by the other indexing utilities are actually necessary to run a disk-based index. Usually the property file and the index files are sufficient: if one needs random access, also the offsets file must be present, and if the compression method requires document sizes or if sizes are requested explicitly, also the sizes file must be present. A StringMap and possibly a PrefixMap will be fetched automatically by getInstance(CharSequence, boolean, boolean) using standard extensions.
Thread safety

A disk-based index is thread safe as long as the offset list, the size list and the term/prefix map are. The static factory methods provided by this class load offsets and sizes using data structures that are thread safe. If you use directly a constructor, instead, it is your responsibility to pass thread-safe data structures.

Since:

1.1

Author:

Sebastiano Vigna

Field Summary

Fields
Modifier and Type	Field	Description
`static int`	`BUFFER_SIZE`	The size of the buffer used by `loadLongBigList(ReadableByteChannel, long, ByteOrder)`.
`static String`	`COUNTS_EXTENSION`	The extension for the counts bitstream.
`static int`	`DEFAULT_OFFSET_STEP`	The default value for the query parameter `Index.UriKeys.OFFSETSTEP`.
`static String`	`FREQUENCIES_EXTENSION`	Standard extension for the file of frequencies.
`static String`	`INDEX_EXTENSION`	Standard extension for the index bitstream.
`static String`	`OCCURRENCIES_EXTENSION`	Standard extension for the file of global counts.
`static String`	`OFFSETS_EXTENSION`	Standard extension for the file of offsets.
`static String`	`OFFSETS_POSTFIX`	The postfix to be added to `POINTERS_EXTENSIONS`, `COUNTS_EXTENSION` and `POSITIONS_EXTENSION` for offsets.
`static String`	`POINTERS_EXTENSIONS`	The extension for the pointers bitstream.
`static String`	`POSITIONS_EXTENSION`	Standard extension for the positions bitstream of a high-performance index.
`static String`	`POSITIONS_NUMBER_OF_BITS_EXTENSION`	Standard extension for the file of lengths of positions.
`static String`	`PREFIXMAP_EXTENSION`	Standard extension for the prefix map.
`static String`	`PROPERTIES_EXTENSION`	Standard extension for the index properties.
`static String`	`SIZES_EXTENSION`	Standard extension for the file of sizes.
`static String`	`STATS_EXTENSION`	Standard extension for the stats file.
`static String`	`SUMS_MAX_POSITION_EXTENSION`	Standard extension for the file of lengths of positions.
`static String`	`TERMMAP_EXTENSION`	Standard extension for the term map.
`static String`	`TERMS_EXTENSION`	Standard extension for the file of terms.
`static String`	`UNSORTED_TERMS_EXTENSION`	Standard extension for the file of terms, unsorted.

Method Summary

Modifier and Type	Method	Description
`static ByteOrder`	`byteOrder(String s)`	Parses a `ByteOrder` value.
`static Index`	`getInstance(IOFactory ioFactory, CharSequence basename, Properties properties, boolean randomAccess, boolean documentSizes, boolean maps, EnumMap<Index.UriKeys,String> queryProperties)`	Returns a new disk-based index, using preloaded `Properties` and possibly guessing reasonable term and prefix maps from the basename.
`static Index`	`getInstance(IOFactory ioFactory, CharSequence basename, Properties properties, StringMap<? extends CharSequence> termMap, PrefixMap<? extends CharSequence> prefixMap, boolean randomAccess, boolean documentSizes, EnumMap<Index.UriKeys,String> queryProperties)`	Returns a new disk-based index, loading exactly the specified parts and using preloaded `Properties`.
`static Index`	`getInstance(CharSequence basename)`	Returns a new local index, trying to guess reasonable term and prefix maps from the basename, loading offsets but loading document sizes only if it is necessary.
`static Index`	`getInstance(CharSequence basename, boolean randomAccess)`	Returns a new local index, trying to guess reasonable term and prefix maps from the basename, and loading document sizes only if it is necessary.
`static Index`	`getInstance(CharSequence basename, boolean randomAccess, boolean documentSizes)`	Returns a new disk-based index, guessing reasonable term and prefix maps from the basename.
`static Index`	`getInstance(CharSequence basename, boolean randomAccess, boolean documentSizes, boolean maps)`	Returns a new disk-based index, using preloaded `Properties` and possibly guessing reasonable term and prefix maps from the basename.
`static Index`	`getInstance(CharSequence basename, boolean randomAccess, boolean documentSizes, boolean maps, EnumMap<Index.UriKeys,String> queryProperties)`	Returns a new disk-based index, possibly guessing reasonable term and prefix maps from the basename.
`static Index`	`getInstance(CharSequence basename, Properties properties, boolean randomAccess, boolean documentSizes, boolean maps, EnumMap<Index.UriKeys,String> queryProperties)`	Returns a new disk-based index, using preloaded `Properties` and possibly guessing reasonable term and prefix maps from the basename.
`static Index`	`getInstance(CharSequence basename, Properties properties, StringMap<? extends CharSequence> termMap, PrefixMap<? extends CharSequence> prefixMap, boolean randomAccess, boolean documentSizes, EnumMap<Index.UriKeys,String> queryProperties)`	Returns a new disk-based index, loading exactly the specified parts and using preloaded `Properties` and the `IOFactory.FILESYSTEM_FACTORY`.
`static LongBigArrayBigList`	`loadLongBigList(IOFactory ioFactory, CharSequence filename, ByteOrder byteOrder)`	Commodity method for loading a big list of binary longs with specified endianness into a long big array.
`static LongBigArrayBigList`	`loadLongBigList(CharSequence filename, ByteOrder byteOrder)`	Commodity method for loading a big list of binary longs with specified endianness into a long big array using the `IOFactory.FILESYSTEM_FACTORY`.
`static LongBigArrayBigList`	`loadLongBigList(ReadableByteChannel channel, long length, ByteOrder byteOrder)`	Commodity method for loading from a channel a big list of binary longs with specified endianness into a long big array.
`static PrefixMap<? extends CharSequence>`	`loadPrefixMap(IOFactory ioFactory, String filename)`	Utility static method that loads a prefix map.
`static PrefixMap<? extends CharSequence>`	`loadPrefixMap(String filename)`	Utility static method that loads a prefix map using the `IOFactory.FILESYSTEM_FACTORY`.
`static StringMap<? extends CharSequence>`	`loadStringMap(IOFactory ioFactory, String filename)`	Utility static method that loads a term map.
`static StringMap<? extends CharSequence>`	`loadStringMap(String filename)`	Utility static method that loads a term map using the `IOFactory.FILESYSTEM_FACTORY`.
`static LongBigList`	`offsets(IOFactory ioFactory, String filename, long numberOfTerms, int offsetStep)`	Returns the list of offsets.
`static LongBigList`	`offsets(String filename, long numberOfTerms, int offsetStep)`	Returns the list of offsets using the `IOFactory.FILESYSTEM_FACTORY`.
`static LongBigList`	`readOffsets(IOFactory ioFactory, CharSequence filename, long T)`	Utility method to load a compressed offset file into a list.
`static LongBigList`	`readOffsets(InputBitStream in, long T)`	Utility method to load a compressed offset file into a list.
`static LongBigList`	`readOffsets(CharSequence filename, long T)`	Utility method to load a compressed offset file into a list using the `IOFactory.FILESYSTEM_FACTORY`.
`static IntBigArrayBigList`	`readSizes(IOFactory ioFactory, CharSequence filename, long n)`	Utility method to load a compressed size file into a list.
`static IntBigArrayBigList`	`readSizes(CharSequence filename, long N)`	Utility method to load a compressed size file into a list using the `IOFactory.FILESYSTEM_FACTORY`.
`static IntBigList`	`readSizesSuccinct(CharSequence filename, long N)`	Deprecated. This method is an ancestral residue.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - DEFAULT_OFFSET_STEP
```
public static final int DEFAULT_OFFSET_STEP
```
    The default value for the query parameter Index.UriKeys.OFFSETSTEP.
    
    See Also:
    
    Constant Field Values
  - INDEX_EXTENSION
```
public static final String INDEX_EXTENSION
```
    Standard extension for the index bitstream.
    
    See Also:
    
    Constant Field Values
  - POSITIONS_EXTENSION
```
public static final String POSITIONS_EXTENSION
```
    Standard extension for the positions bitstream of a high-performance index.
    
    See Also:
    
    Constant Field Values
  - PROPERTIES_EXTENSION
```
public static final String PROPERTIES_EXTENSION
```
    Standard extension for the index properties.
    
    See Also:
    
    Constant Field Values
  - SIZES_EXTENSION
```
public static final String SIZES_EXTENSION
```
    Standard extension for the file of sizes.
    
    See Also:
    
    Constant Field Values
  - OFFSETS_EXTENSION
```
public static final String OFFSETS_EXTENSION
```
    Standard extension for the file of offsets.
    
    See Also:
    
    Constant Field Values
  - POSITIONS_NUMBER_OF_BITS_EXTENSION
```
public static final String POSITIONS_NUMBER_OF_BITS_EXTENSION
```
    Standard extension for the file of lengths of positions.
    
    See Also:
    
    Constant Field Values
  - SUMS_MAX_POSITION_EXTENSION
```
public static final String SUMS_MAX_POSITION_EXTENSION
```
    Standard extension for the file of lengths of positions.
    
    See Also:
    
    Constant Field Values
  - OCCURRENCIES_EXTENSION
```
public static final String OCCURRENCIES_EXTENSION
```
    Standard extension for the file of global counts.
    
    See Also:
    
    Constant Field Values
  - FREQUENCIES_EXTENSION
```
public static final String FREQUENCIES_EXTENSION
```
    Standard extension for the file of frequencies.
    
    See Also:
    
    Constant Field Values
  - TERMS_EXTENSION
```
public static final String TERMS_EXTENSION
```
    Standard extension for the file of terms.
    
    See Also:
    
    Constant Field Values
  - UNSORTED_TERMS_EXTENSION
```
public static final String UNSORTED_TERMS_EXTENSION
```
    Standard extension for the file of terms, unsorted.
    
    See Also:
    
    Constant Field Values
  - TERMMAP_EXTENSION
```
public static final String TERMMAP_EXTENSION
```
    Standard extension for the term map.
    
    See Also:
    
    Constant Field Values
  - PREFIXMAP_EXTENSION
```
public static final String PREFIXMAP_EXTENSION
```
    Standard extension for the prefix map.
    
    See Also:
    
    Constant Field Values
  - STATS_EXTENSION
```
public static final String STATS_EXTENSION
```
    Standard extension for the stats file.
    
    See Also:
    
    Constant Field Values
  - POINTERS_EXTENSIONS
```
public static final String POINTERS_EXTENSIONS
```
    The extension for the pointers bitstream.
    
    See Also:
    
    Constant Field Values
  - COUNTS_EXTENSION
```
public static final String COUNTS_EXTENSION
```
    The extension for the counts bitstream.
    
    See Also:
    
    Constant Field Values
  - OFFSETS_POSTFIX
```
public static final String OFFSETS_POSTFIX
```
    The postfix to be added to POINTERS_EXTENSIONS, COUNTS_EXTENSION and POSITIONS_EXTENSION for offsets.
    
    See Also:
    
    Constant Field Values
  - BUFFER_SIZE
```
public static final int BUFFER_SIZE
```
    The size of the buffer used by loadLongBigList(ReadableByteChannel, long, ByteOrder).
    
    See Also:
    
    Constant Field Values
- Method Detail
  - readOffsets
```
public static LongBigList readOffsets(InputBitStream in,
                                      long T)
                               throws IOException
```
    Utility method to load a compressed offset file into a list.
    
    Parameters:
    
    in - the input bit stream providing the offsets (see BitStreamIndexWriter).
    
    T - the number of terms indexed.
    
    Returns:
    
    a list of longs backed by an array; the list has an additional final element of index T that gives the number of bytes of the index file.
    
    Throws:
    
    IOException
  - readOffsets
```
public static LongBigList readOffsets(IOFactory ioFactory,
                                      CharSequence filename,
                                      long T)
                               throws IOException
```
    Utility method to load a compressed offset file into a list.
    
    Parameters:
    
    ioFactory - the factory that will be used to perform I/O.
    
    filename - the file containing the offsets (see BitStreamIndexWriter).
    
    T - the number of terms indexed.
    
    Returns:
    
    a list of longs backed by an array; the list has an additional final element of index T that gives the number of bytes of the index file.
    
    Throws:
    
    IOException
  - readOffsets
```
public static LongBigList readOffsets(CharSequence filename,
                                      long T)
                               throws IOException
```
    Utility method to load a compressed offset file into a list using the IOFactory.FILESYSTEM_FACTORY.
    
    Parameters:
    
    filename - the file containing the offsets (see BitStreamIndexWriter).
    
    T - the number of terms indexed.
    
    Returns:
    
    a list of longs backed by an array; the list has an additional final element of index T that gives the number of bytes of the index file.
    
    Throws:
    
    IOException
  - readSizes
```
public static IntBigArrayBigList readSizes(IOFactory ioFactory,
                                           CharSequence filename,
                                           long n)
                                    throws IOException
```
    Utility method to load a compressed size file into a list.
    
    Parameters:
    
    ioFactory - the factory that will be used to perform I/O.
    
    filename - the file containing the γ-coded sizes (see BitStreamIndexWriter).
    
    n - the number of documents.
    
    Returns:
    
    a list of integers backed by an array.
    
    Throws:
    
    IOException
  - readSizes
```
public static IntBigArrayBigList readSizes(CharSequence filename,
                                           long N)
                                    throws IOException
```
    Utility method to load a compressed size file into a list using the IOFactory.FILESYSTEM_FACTORY.
    
    Parameters:
    
    filename - the file containing the γ-coded sizes (see BitStreamIndexWriter).
    
    N - the number of documents.
    
    Returns:
    
    a list of integers backed by an array.
    
    Throws:
    
    IOException
  - readSizesSuccinct
```
@Deprecated
public static IntBigList readSizesSuccinct(CharSequence filename,
                                           long N)
                                    throws IOException
```
    Deprecated.
    This method is an ancestral residue.
    
    Utility method to load a compressed size file into an Elias–Fano compressed list.
    
    Parameters:
    
    filename - the filename containing the γ-coded sizes (see BitStreamIndexWriter).
    
    N - the number of documents indexed.
    
    Returns:
    
    a list of integers backed by an Elias–Fano compressed list.
    
    Throws:
    
    IllegalStateException - if ioFactory is not IOFactory.FILESYSTEM_FACTORY.
    
    IOException
  - loadLongBigList
```
public static LongBigArrayBigList loadLongBigList(IOFactory ioFactory,
                                                  CharSequence filename,
                                                  ByteOrder byteOrder)
                                           throws IOException
```
    Commodity method for loading a big list of binary longs with specified endianness into a long big array.
    
    Parameters:
    
    ioFactory - the factory that will be used to perform I/O.
    
    filename - the file containing the longs.
    
    byteOrder - the endianness of the longs.
    
    Returns:
    
    a big list of longs containing the longs in file.
    
    Throws:
    
    IOException
  - loadLongBigList
```
public static LongBigArrayBigList loadLongBigList(CharSequence filename,
                                                  ByteOrder byteOrder)
                                           throws IOException
```
    Commodity method for loading a big list of binary longs with specified endianness into a long big array using the IOFactory.FILESYSTEM_FACTORY.
    
    Parameters:
    
    filename - the file containing the longs.
    
    byteOrder - the endianness of the longs.
    
    Returns:
    
    a big list of longs containing the longs in file.
    
    Throws:
    
    IOException
  - loadLongBigList
```
public static LongBigArrayBigList loadLongBigList(ReadableByteChannel channel,
                                                  long length,
                                                  ByteOrder byteOrder)
                                           throws IOException
```
    Commodity method for loading from a channel a big list of binary longs with specified endianness into a long big array.
    
    Parameters:
    
    channel - the channel.
    
    byteOrder - the endianness of the longs.
    
    Returns:
    
    a big list of longs containing the longs returned by channel.
    
    Throws:
    
    IOException
  - byteOrder
```
public static ByteOrder byteOrder(String s)
```
    Parses a ByteOrder value.
    
    Parameters:
    
    s - a string (either BIG_ENDIAN or LITTLE_ENDIAN).
    
    Returns:
    
    the corresponding byte order (ByteOrder.BIG_ENDIAN or ByteOrder.LITTLE_ENDIAN).
  - loadStringMap
```
public static StringMap<? extends CharSequence> loadStringMap(IOFactory ioFactory,
                                                              String filename)
                                                       throws IOException
```
    Utility static method that loads a term map.
    
    Parameters:
    
    ioFactory - the factory that will be used to perform I/O.
    
    filename - the name of the file containing the term map.
    
    Returns:
    
    the map, or null if the file did not exist.
    
    Throws:
    
    IOException - if some IOException (other than FileNotFoundException) occurred.
  - loadStringMap
```
public static StringMap<? extends CharSequence> loadStringMap(String filename)
                                                       throws IOException
```
    Utility static method that loads a term map using the IOFactory.FILESYSTEM_FACTORY.
    
    Parameters:
    
    filename - the name of the file containing the term map.
    
    Returns:
    
    the map, or null if the file did not exist.
    
    Throws:
    
    IOException - if some IOException (other than FileNotFoundException) occurred.
  - loadPrefixMap
```
public static PrefixMap<? extends CharSequence> loadPrefixMap(IOFactory ioFactory,
                                                              String filename)
                                                       throws IOException
```
    Utility static method that loads a prefix map.
    
    Parameters:
    
    ioFactory - the factory that will be used to perform I/O.
    
    filename - the name of the file containing the prefix map.
    
    Returns:
    
    the map, or null if the file did not exist.
    
    Throws:
    
    IOException - if some IOException (other than FileNotFoundException) occurred.
  - loadPrefixMap
```
public static PrefixMap<? extends CharSequence> loadPrefixMap(String filename)
                                                       throws IOException
```
    Utility static method that loads a prefix map using the IOFactory.FILESYSTEM_FACTORY.
    
    Parameters:
    
    filename - the name of the file containing the prefix map.
    
    Returns:
    
    the map, or null if the file did not exist.
    
    Throws:
    
    IOException - if some IOException (other than FileNotFoundException) occurred.
  - offsets
```
public static LongBigList offsets(IOFactory ioFactory,
                                  String filename,
                                  long numberOfTerms,
                                  int offsetStep)
                           throws FileNotFoundException,
                                  IOException
```
    Returns the list of offsets.
    
    Parameters:
    
    ioFactory - the factory that will be used to perform I/O.
    
    filename - the file containing the offsets.
    
    numberOfTerms - the number of terms.
    
    offsetStep - the offset step.
    
    Returns:
    
    if offsetStep is less than zero, a memory-mapped, synchronized SemiExternalOffsetBigList with offset step equal to -offsetStep; if it is zero, an in-memory list; if it is greater than than zero, we return a synchronized SemiExternalOffsetBigList with offset step equal to -offsetStep.
    
    Throws:
    
    FileNotFoundException
    
    IOException
  - offsets
```
public static LongBigList offsets(String filename,
                                  long numberOfTerms,
                                  int offsetStep)
                           throws FileNotFoundException,
                                  IOException
```
    Returns the list of offsets using the IOFactory.FILESYSTEM_FACTORY.
    
    Parameters:
    
    filename - the file containing the offsets.
    
    numberOfTerms - the number of terms.
    
    offsetStep - the offset step.
    
    Returns:
    
    if offsetStep is less than zero, a memory-mapped, synchronized SemiExternalOffsetBigList with offset step equal to -offsetStep; if it is zero, an in-memory list; if it is greater than than zero, we return a synchronized SemiExternalOffsetBigList with offset step equal to -offsetStep.
    
    Throws:
    
    FileNotFoundException
    
    IOException
  - getInstance
```
public static Index getInstance(IOFactory ioFactory,
                                CharSequence basename,
                                Properties properties,
                                StringMap<? extends CharSequence> termMap,
                                PrefixMap<? extends CharSequence> prefixMap,
                                boolean randomAccess,
                                boolean documentSizes,
                                EnumMap<Index.UriKeys,String> queryProperties)
                         throws ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new disk-based index, loading exactly the specified parts and using preloaded Properties.
    
    Parameters:
    
    ioFactory - the factory that will be used to perform I/O.
    
    basename - the basename of the index.
    
    properties - the properties obtained from the given basename.
    
    termMap - the term map for this index, or null for no term map.
    
    prefixMap - the prefix map for this index, or null for no prefix map.
    
    randomAccess - whether the index should be accessible randomly (e.g., if it will be possible to call IndexReader.documents(long) on the index readers returned by the index).
    
    documentSizes - if true, document sizes will be loaded (note that sometimes document sizes might be loaded anyway because the compression method for positions requires it).
    
    queryProperties - a map containing associations between Index.UriKeys and values, or null.
    
    Throws:
    
    ClassNotFoundException
    
    IOException
    
    InstantiationException
    
    IllegalAccessException
  - getInstance
```
public static Index getInstance(CharSequence basename,
                                Properties properties,
                                StringMap<? extends CharSequence> termMap,
                                PrefixMap<? extends CharSequence> prefixMap,
                                boolean randomAccess,
                                boolean documentSizes,
                                EnumMap<Index.UriKeys,String> queryProperties)
                         throws ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new disk-based index, loading exactly the specified parts and using preloaded Properties and the IOFactory.FILESYSTEM_FACTORY.
    
    Parameters:
    
    basename - the basename of the index.
    
    properties - the properties obtained from the given basename.
    
    termMap - the term map for this index, or null for no term map.
    
    prefixMap - the prefix map for this index, or null for no prefix map.
    
    randomAccess - whether the index should be accessible randomly (e.g., if it will be possible to call IndexReader.documents(long) on the index readers returned by the index).
    
    documentSizes - if true, document sizes will be loaded (note that sometimes document sizes might be loaded anyway because the compression method for positions requires it).
    
    queryProperties - a map containing associations between Index.UriKeys and values, or null.
    
    Throws:
    
    ClassNotFoundException
    
    IOException
    
    InstantiationException
    
    IllegalAccessException
  - getInstance
```
public static Index getInstance(IOFactory ioFactory,
                                CharSequence basename,
                                Properties properties,
                                boolean randomAccess,
                                boolean documentSizes,
                                boolean maps,
                                EnumMap<Index.UriKeys,String> queryProperties)
                         throws ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new disk-based index, using preloaded Properties and possibly guessing reasonable term and prefix maps from the basename.
    
    Parameters:
    
    ioFactory - the factory that will be used to perform I/O.
    
    basename - the basename of the index.
    
    properties - the properties obtained by stemming basename.
    
    randomAccess - whether the index should be accessible randomly.
    
    documentSizes - if true, document sizes will be loaded.
    
    maps - if true, term and prefix maps will be guessed and loaded.
    
    queryProperties - a map containing associations between Index.UriKeys and values, or null.
    
    Throws:
    
    IllegalAccessException
    
    InstantiationException
    
    ClassNotFoundException
    
    IOException
    
    See Also:
    
    getInstance(CharSequence, Properties, StringMap, PrefixMap, boolean, boolean, EnumMap)
  - getInstance
```
public static Index getInstance(CharSequence basename,
                                Properties properties,
                                boolean randomAccess,
                                boolean documentSizes,
                                boolean maps,
                                EnumMap<Index.UriKeys,String> queryProperties)
                         throws ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new disk-based index, using preloaded Properties and possibly guessing reasonable term and prefix maps from the basename.
    
    Parameters:
    
    basename - the basename of the index.
    
    properties - the properties obtained by stemming basename.
    
    randomAccess - whether the index should be accessible randomly.
    
    documentSizes - if true, document sizes will be loaded.
    
    maps - if true, term and prefix maps will be guessed and loaded.
    
    queryProperties - a map containing associations between Index.UriKeys and values, or null.
    
    Throws:
    
    IllegalAccessException
    
    InstantiationException
    
    ClassNotFoundException
    
    IOException
    
    See Also:
    
    getInstance(CharSequence, Properties, StringMap, PrefixMap, boolean, boolean, EnumMap)
  - getInstance
```
public static Index getInstance(CharSequence basename,
                                boolean randomAccess,
                                boolean documentSizes,
                                boolean maps,
                                EnumMap<Index.UriKeys,String> queryProperties)
                         throws org.apache.commons.configuration.ConfigurationException,
                                ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new disk-based index, possibly guessing reasonable term and prefix maps from the basename.
    If there is a term map file (basename stemmed with .termmap), it is used as term map and, in case it implements PrefixMap. Otherwise, we search for a prefix map (basename stemmed with .prefixmap) and, if it implements StringMap and no term map has been found, we use it as prefix map.
    
    Parameters:
    
    basename - the basename of the index.
    
    randomAccess - whether the index should be accessible randomly (e.g., if it will be possible to call IndexReader.documents(long) on the index readers returned by the index).
    
    documentSizes - if true, document sizes will be loaded (note that sometimes document sizes might be loaded anyway because the compression method for positions requires it).
    
    maps - if true, term and prefix maps will be guessed and loaded (this feature might not be available with some kind of index).
    
    queryProperties - a map containing associations between Index.UriKeys and values, or null.
    
    Throws:
    
    org.apache.commons.configuration.ConfigurationException
    
    ClassNotFoundException
    
    IOException
    
    InstantiationException
    
    IllegalAccessException
  - getInstance
```
public static Index getInstance(CharSequence basename,
                                boolean randomAccess,
                                boolean documentSizes,
                                boolean maps)
                         throws org.apache.commons.configuration.ConfigurationException,
                                ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new disk-based index, using preloaded Properties and possibly guessing reasonable term and prefix maps from the basename.
    If there is a term map file (basename stemmed with .termmap), it is used as term map and, in case it implements PrefixMap. Otherwise, we search for a prefix map (basename stemmed with .prefixmap) and, if it implements StringMap and no term map has been found, we use it as prefix map.
    
    Parameters:
    
    basename - the basename of the index.
    
    randomAccess - whether the index should be accessible randomly (e.g., if it will be possible to call IndexReader.documents(long) on the index readers returned by the index).
    
    documentSizes - if true, document sizes will be loaded (note that sometimes document sizes might be loaded anyway because the compression method for positions requires it).
    
    maps - if true, term and prefix maps will be guessed and loaded (this feature might not be available with some kind of index).
    
    Throws:
    
    org.apache.commons.configuration.ConfigurationException
    
    ClassNotFoundException
    
    IOException
    
    InstantiationException
    
    IllegalAccessException
    
    See Also:
    
    getInstance(CharSequence, boolean, boolean, boolean, EnumMap)
  - getInstance
```
public static Index getInstance(CharSequence basename,
                                boolean randomAccess,
                                boolean documentSizes)
                         throws org.apache.commons.configuration.ConfigurationException,
                                ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new disk-based index, guessing reasonable term and prefix maps from the basename.
    
    Parameters:
    
    basename - the basename of the index.
    
    randomAccess - whether the index should be accessible randomly (e.g., if it will be possible to call IndexReader.documents(long) on the index readers returned by the index).
    
    documentSizes - if true, document sizes will be loaded (note that sometimes document sizes might be loaded anyway because the compression method for positions requires it).
    
    Throws:
    
    org.apache.commons.configuration.ConfigurationException
    
    ClassNotFoundException
    
    IOException
    
    InstantiationException
    
    IllegalAccessException
  - getInstance
```
public static Index getInstance(CharSequence basename,
                                boolean randomAccess)
                         throws org.apache.commons.configuration.ConfigurationException,
                                ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new local index, trying to guess reasonable term and prefix maps from the basename, and loading document sizes only if it is necessary.
    
    Parameters:
    
    basename - the basename of the index.
    
    randomAccess - whether the index should be accessible randomly (e.g., if it will be possible to call IndexReader.documents(long) on the index readers returned by the index).
    
    Throws:
    
    org.apache.commons.configuration.ConfigurationException
    
    ClassNotFoundException
    
    IOException
    
    InstantiationException
    
    IllegalAccessException
  - getInstance
```
public static Index getInstance(CharSequence basename)
                         throws org.apache.commons.configuration.ConfigurationException,
                                ClassNotFoundException,
                                IOException,
                                InstantiationException,
                                IllegalAccessException
```
    Returns a new local index, trying to guess reasonable term and prefix maps from the basename, loading offsets but loading document sizes only if it is necessary.
    
    Parameters:
    
    basename - the basename of the index.
    
    Throws:
    
    org.apache.commons.configuration.ConfigurationException
    
    ClassNotFoundException
    
    IOException
    
    InstantiationException
    
    IllegalAccessException

Class DiskBasedIndex

Thread safety

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

DEFAULT_OFFSET_STEP

INDEX_EXTENSION

POSITIONS_EXTENSION

PROPERTIES_EXTENSION

SIZES_EXTENSION

OFFSETS_EXTENSION

POSITIONS_NUMBER_OF_BITS_EXTENSION

SUMS_MAX_POSITION_EXTENSION

OCCURRENCIES_EXTENSION

FREQUENCIES_EXTENSION

TERMS_EXTENSION

UNSORTED_TERMS_EXTENSION

TERMMAP_EXTENSION

PREFIXMAP_EXTENSION

STATS_EXTENSION

POINTERS_EXTENSIONS

COUNTS_EXTENSION

OFFSETS_POSTFIX

BUFFER_SIZE

Method Detail

readOffsets

readOffsets

readOffsets

readSizes

readSizes

readSizesSuccinct

loadLongBigList

loadLongBigList

loadLongBigList

byteOrder

loadStringMap

loadStringMap

loadPrefixMap

loadPrefixMap

offsets

offsets

getInstance

getInstance

getInstance

getInstance

getInstance

getInstance

getInstance

getInstance

getInstance