Package it.unimi.di.big.mg4j.tool

Class URLMPHVirtualDocumentResolver

java.lang.Object

it.unimi.di.big.mg4j.tool.URLMPHVirtualDocumentResolver

All Implemented Interfaces:

VirtualDocumentResolver, Serializable

public class URLMPHVirtualDocumentResolver
extends Object
implements VirtualDocumentResolver

A virtual-document resolver based on document URIs.

Instances of this class store in a StringMap instances all URIs from a collection, and consider a virtual-document specification a (possibly relative) URI. The virtual-document specification is resolved against the document URI, and then the perfect hash is used to retrieve the corresponding document.

This class provides a main method that helps in building serialised resolvers from URI lists. In case of pathological document collections with duplicate URIs (most notably, the GOV2 collection used for TREC evaluations), an option makes it possible to add random noise to duplicates, so that minimal perfect hash construction does not go into an infinite loop. It is a rather crude solution, but it is nonsensical to have duplicate URIs in the first place. Additional option include the kind of minimal perfect hash function you want to use (e.g., out of it.unimi.dsi.sux4j) and the number of bits used to sign them.

Warning: up to version 5.2.1, this class was applying URI.normalize() in context(Document) and resolve(CharSequence) methods. This does not happen any longer, as it was breaking URLs such as http://en.wikipedia.org/wiki//dev/null.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
URLMPHVirtualDocumentResolver(StringMap<? extends CharSequence> url2DocumentPointer)

Method Summary

Modifier and Type	Method	Description
void	context(Document document)	Sets the context document.
static void	main(String[] arg)
long	numberOfDocuments()	Returns the number of documents handled by this resolver, if it is known.
long	resolve(CharSequence virtualDocumentSpec)	Resolves a virtual document specification.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

URLMPHVirtualDocumentResolver

public URLMPHVirtualDocumentResolver(StringMap<? extends CharSequence> url2DocumentPointer)

Method Detail

context

public void context(Document document)

Description copied from interface: VirtualDocumentResolver

Sets the context document. All successive calls to VirtualDocumentResolver.resolve(CharSequence) will assume the virtual-document specification was found in document.

Specified by:

context in interface VirtualDocumentResolver

Parameters:

document - the context document.

resolve

public long resolve(CharSequence virtualDocumentSpec)

Description copied from interface: VirtualDocumentResolver

Resolves a virtual document specification.

Note that the resolution process is carried out in the context of the last document passed to VirtualDocumentResolver.context(Document) (e.g., for relative URI resolution). If VirtualDocumentResolver.context(Document) was never called, the behaviour is undefined.

Specified by:

resolve in interface VirtualDocumentResolver

Parameters:

virtualDocumentSpec - the virtual document specification.

Returns:

the document virtualDocumentSpec refers to, or -1 if the specification could not be resolved.

numberOfDocuments

public long numberOfDocuments()

Description copied from interface: VirtualDocumentResolver

Returns the number of documents handled by this resolver, if it is known. A call to VirtualDocumentResolver.resolve(CharSequence) will always return a number smaller than the one returned by this method.

Specified by:

numberOfDocuments in interface VirtualDocumentResolver

Returns:

the number of documents handled by this resolver.

main

public static void main(String[] arg)
                 throws com.martiansoftware.jsap.JSAPException,
                        IOException

Throws:

com.martiansoftware.jsap.JSAPException

IOException