package org.basex.index;
import org.basex.core.*;
import org.basex.index.query.*;
/**
* This interface defines the methods which have to be implemented
* by an index structure.
*
* @author BaseX Team 2005-17, BSD License
* @author Christian Gruen
*/
public interface Index {
/**
* Returns information on the index structure.
* @param options main options
* @return info
*/
byte[] info(MainOptions options);
/**
* Returns all entries that match the specified token.
* @param entries index entries
* @return entries
*/
EntryIterator entries(IndexEntries entries);
/**
* Returns an iterator for the index results.
* @param token token to be found
* @return sorted pre values for the token
*/
IndexIterator iter(IndexToken token);
/**
* Computes costs for accessing the specified token. An integer is returned:
* <ul>
* <li> A negative zero indicates that index access is not possible.</li>
* <li> A value of zero indicates that no results will be returned.</li>
* <li> A small value indicates that index access is fast.</li>
* </ul>
* Smaller values are better, a value of zero indicates that no results will be returned.
* @param token token to be found
* @return cost estimation
*/
int costs(IndexToken token);
/**
* Drops the index. Also returns true if the index does not exist.
* @return success flag
*/
boolean drop();
/**
* Closes the index.
*/
void close();
}