it.unimi.di.mg4j.search
Class DocumentIteratorBuilderVisitor

java.lang.Object
  it.unimi.di.mg4j.query.nodes.AbstractQueryBuilderVisitor<DocumentIterator>
      it.unimi.di.mg4j.search.DocumentIteratorBuilderVisitor

All Implemented Interfaces:

QueryBuilderVisitor<DocumentIterator>, FlyweightPrototype<QueryBuilderVisitor<DocumentIterator>>

Direct Known Subclasses:

PrecomputeIndex.ReplacingDocumentIteratorBuilderVisitor

public class DocumentIteratorBuilderVisitor
extends AbstractQueryBuilderVisitor<DocumentIterator>

A QueryBuilderVisitor that builds a DocumentIterator resolving the queries using the objects in it.unimi.di.mg4j.search.

This elementary builder visitor invokes Index.documents(CharSequence) to build the leaf index iterators. Thus, the resulting DocumentIterator should be carefully disposed after usage (every index iterator may open a file or a socket).

Prefix and MultiTerm nodes cause the creation of a MultiTermIndexIterator, in the first case by calling Index.documents(CharSequence,int) and in the second case by creating a MultiTermIndexIterator with the name and frequency equal to the maximum frequency over all terms. Other implementations might choose differently.

At construction time, you must provide a map from strings to indices that will be used to resolve Select nodes. The map may be null, in which case such nodes will cause an IllegalArgumentException. If a Select node contains an index name that does not appear in the map a NoSuchElementException will be thrown instead.

A production site will likely substitute this builder visitor with one that reuses index readers out of a pool.

Instances of this class may be safely reused by calling prepare().

Field Summary

protected ObjectArrayList<Index>	curr The stack of selected indices (changed by Select nodes).
protected Index	defaultIndex The default index.
protected Reference2ReferenceMap<Index,Object>	index2Parser A map associating an object with a parse(String) method to each payload-based index.
protected Object2ReferenceMap<String,Index>	indexMap A map associating a textual key to indices.
protected int	limit The limit on prefix queries provided in the constructor.
protected int	numberOfDocuments The number of documents (fetched from the default index).
protected double	weight The last seen, but still not consumed, weight, or Double.NaN.
protected DoubleArrayList	weights The stack of weights.

Constructor Summary

DocumentIteratorBuilderVisitor(Object2ReferenceMap<String,Index> indexMap, Index defaultIndex, int limit)
Creates a new builder visitor.

DocumentIteratorBuilderVisitor(Object2ReferenceMap<String,Index> indexMap, Reference2ReferenceMap<Index,Object> index2Parser, Index defaultIndex, int limit)
Creates a new builder visitor with additional parsers for payload-based indices.

Method Summary

DocumentIteratorBuilderVisitor	copy()
DocumentIterator[]	newArray(int len) Builds an array of given length of type T.
DocumentIteratorBuilderVisitor	prepare() No-op.
protected void	pushWeight() Pushes weight, if it is not Double.NaN, or 1, otherwise, on the stack of weights; in either case, sets weight to Double.NaN.
DocumentIterator	visit(False node) Visits False.
DocumentIterator	visit(Prefix node) Visits a Prefix.
DocumentIterator	visit(Range node) Visits a Range.
DocumentIterator	visit(Term node) Visits a Term.
DocumentIterator	visit(True node) Visits True.
DocumentIterator	visitPost(Align node, DocumentIterator[] subNode) Visits an Align node after recursing into the corresponding subtree.
DocumentIterator	visitPost(And node, DocumentIterator[] subNode) Visits an And node after recursing into the corresponding subtree.
DocumentIterator	visitPost(Consecutive node, DocumentIterator[] subNode) Visits a Consecutive node after recursing into the corresponding subtree.
DocumentIterator	visitPost(Difference node, DocumentIterator[] subNode) Visits an Difference node after recursing into the corresponding subtree.
DocumentIterator	visitPost(LowPass node, DocumentIterator subNode) Visits a LowPass node after recursing into the corresponding subtree.
DocumentIterator	visitPost(MultiTerm node, DocumentIterator[] subNode) Visits a MultiTerm node after recursing into the corresponding subtree.
DocumentIterator	visitPost(Not node, DocumentIterator subNode) Visits a Not node after recursing into the corresponding subtree.
DocumentIterator	visitPost(OrderedAnd node, DocumentIterator[] subNode) Visits an OrderedAnd node after recursing into the corresponding subtree.
DocumentIterator	visitPost(Or node, DocumentIterator[] subNode) Visits an Or node after recursing into the corresponding subtree.
DocumentIterator	visitPost(Remap node, DocumentIterator subNode) Visits a Remap node after recursing into the corresponding subtree.
DocumentIterator	visitPost(Select node, DocumentIterator subNode) Visits a Select node after recursing into the corresponding subtree.
DocumentIterator	visitPost(Weight node, DocumentIterator subNode) Visits a Weight node after recursing into the corresponding subtree.
boolean	visitPre(Align node) Visits an Align node before recursing into the corresponding subtree.
boolean	visitPre(And node) Visits an And node before recursing into the corresponding subtree.
boolean	visitPre(Consecutive node) Visits a Consecutive node before recursing into the corresponding subtree.
boolean	visitPre(Difference node) Visits an Difference node before recursing into the corresponding subtree.
boolean	visitPre(LowPass node) Visits a LowPass node before recursing into the corresponding subtree.
boolean	visitPre(MultiTerm node) Visits a MultiTerm node before recursing into the corresponding subtree.
boolean	visitPre(Not node) Visits a Not node before recursing into the corresponding subtree.
boolean	visitPre(Or node) Visits an Or node before recursing into the corresponding subtree.
boolean	visitPre(OrderedAnd node) Visits an OrderedAnd node before recursing into the corresponding subtree.
boolean	visitPre(Remap node) Visits a Remap node before recursing into the corresponding subtree.
boolean	visitPre(Select node) Visits a Select node before recursing into the corresponding subtree.
boolean	visitPre(Weight node) Visits a Weight node before recursing into the corresponding subtree.
protected double	weight() Returns weight, if it is not Double.NaN, or 1, otherwise; in either case, sets weight to Double.NaN.

Methods inherited from class java.lang.Object

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

Field Detail

indexMap

protected final Object2ReferenceMap<String,Index> indexMap

A map associating a textual key to indices.

index2Parser

protected final Reference2ReferenceMap<Index,Object> index2Parser

A map associating an object with a parse(String) method to each payload-based index.

defaultIndex

protected final Index defaultIndex

The default index.

numberOfDocuments

protected final int numberOfDocuments

The number of documents (fetched from the default index).

limit

protected final int limit

The limit on prefix queries provided in the constructor.

curr

protected ObjectArrayList<Index> curr

The stack of selected indices (changed by Select nodes).

weights

protected DoubleArrayList weights

The stack of weights.

weight

protected double weight

The last seen, but still not consumed, weight, or Double.NaN.

Constructor Detail

DocumentIteratorBuilderVisitor

public DocumentIteratorBuilderVisitor(Object2ReferenceMap<String,Index> indexMap,
                                      Index defaultIndex,
                                      int limit)

Creates a new builder visitor.

Parameters:

indexMap - a map from index names to indices, to be used in Select nodes, or null if the only used index is the default index.

defaultIndex - the default index.

limit - a limit that will be used with Prefix nodes.

DocumentIteratorBuilderVisitor

public DocumentIteratorBuilderVisitor(Object2ReferenceMap<String,Index> indexMap,
                                      Reference2ReferenceMap<Index,Object> index2Parser,
                                      Index defaultIndex,
                                      int limit)

Creates a new builder visitor with additional parsers for payload-based indices.

Parameters:

indexMap - a map from index names to indices, to be used in Select nodes, or null if the only used index is the default index.

defaultIndex - the default index.

limit - a limit that will be used with Prefix nodes.

Method Detail

pushWeight

protected void pushWeight()

Pushes weight, if it is not Double.NaN, or 1, otherwise, on the stack of weights; in either case, sets weight to Double.NaN.

weight

protected double weight()

Returns weight, if it is not Double.NaN, or 1, otherwise; in either case, sets weight to Double.NaN.

Returns:

weight, if it is not Double.NaN, or 1, otherwise.

copy

public DocumentIteratorBuilderVisitor copy()

prepare

public DocumentIteratorBuilderVisitor prepare()

Description copied from class: AbstractQueryBuilderVisitor

No-op.

Specified by:

prepare in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

prepare in class AbstractQueryBuilderVisitor<DocumentIterator>

Returns:

this visitor.

newArray

public DocumentIterator[] newArray(int len)

Description copied from interface: QueryBuilderVisitor

Builds an array of given length of type T.

Because of erasure, generic classes in Java cannot allocate arrays of generic types. This impossibility can be a problem if for some reason the visitPost() methods expect an actual array of type T. This method must provide an array of given length that is an acceptable input for all visitPost() methods.

Note that by declaring an implementing class of this interface that has a sole constructor accepting an argument of type Class<T>, you will force the user to provide the class of the generic type, opening the way for the reflective methods in Array.

Parameters:

len - the required array length.

Returns:

an array of type T of length len.

visit

public DocumentIterator visit(Term node)
                       throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Term.

Parameters:

node - the leaf to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visit

public DocumentIterator visit(Prefix node)
                       throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Prefix.

Parameters:

node - the leaf to be visited.

Returns:

an appropriate return value (usually, the object built using the elements in subNodeResult) if the visit should continue, or null.

Throws:

QueryBuilderVisitorException

visit

public DocumentIterator visit(Range node)
                       throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Range.

Parameters:

node - the leaf to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPre

public boolean visitPre(And node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an And node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(And node,
                                  DocumentIterator[] subNode)
                           throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an And node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the array of results returned by subnodes.

Returns:

an appropriate return value (usually, the object built using the elements in subNodeResult) if the visit should continue, or null.

Throws:

QueryBuilderVisitorException

visitPre

public boolean visitPre(Consecutive node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Consecutive node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(Consecutive node,
                                  DocumentIterator[] subNode)
                           throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Consecutive node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the array of results returned by subnodes.

Returns:

an appropriate return value (usually, the object built using the elements in subNodeResult) if the visit should continue, or null.

Throws:

QueryBuilderVisitorException

visitPre

public boolean visitPre(LowPass node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a LowPass node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(LowPass node,
                                  DocumentIterator subNode)

Description copied from interface: QueryBuilderVisitor

Visits a LowPass node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the of result returned by the sole subnode.

Returns:

an appropriate return value (usually, the object built using subNodeResult) if the visit should continue, or null.

visitPre

public boolean visitPre(Not node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Not node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(Not node,
                                  DocumentIterator subNode)
                           throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Not node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the of result returned by the sole subnode.

Returns:

an appropriate return value (usually, the object built using subNodeResult) if the visit should continue, or null.

Throws:

QueryBuilderVisitorException

visitPre

public boolean visitPre(Or node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an Or node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(Or node,
                                  DocumentIterator[] subNode)
                           throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an Or node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

Returns:

an appropriate return value (usually, the object built using the elements in subNodeResult) if the visit should continue, or null.

Throws:

QueryBuilderVisitorException

visitPre

public boolean visitPre(OrderedAnd node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an OrderedAnd node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(OrderedAnd node,
                                  DocumentIterator[] subNode)
                           throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an OrderedAnd node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the array of results returned by subnodes.

Returns:

an appropriate return value (usually, the object built using the elements in subNodeResult) if the visit should continue, or null.

Throws:

QueryBuilderVisitorException

visitPre

public boolean visitPre(Align node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an Align node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(Align node,
                                  DocumentIterator[] subNode)
                           throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an Align node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the array of results returned by subnodes.

Returns:

an appropriate return value (usually, the object built using the elements in subNodeResult) if the visit should continue, or null.

Throws:

QueryBuilderVisitorException

visitPre

public boolean visitPre(Difference node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits an Difference node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(Difference node,
                                  DocumentIterator[] subNode)

Description copied from interface: QueryBuilderVisitor

Visits an Difference node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the array of results returned by subnodes.

Returns:

an appropriate return value (usually, the object built using the elements in subNodeResult) if the visit should continue, or null.

visitPre

public boolean visitPre(MultiTerm node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a MultiTerm node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(MultiTerm node,
                                  DocumentIterator[] subNode)
                           throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a MultiTerm node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the of result returned by the sole subnode.

Returns:

an appropriate return value (usually, the object built using subNodeResult) if the visit should continue, or null.

Throws:

QueryBuilderVisitorException

visitPre

public boolean visitPre(Select node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Select node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(Select node,
                                  DocumentIterator subNode)

Description copied from interface: QueryBuilderVisitor

Visits a Select node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the of result returned by the sole subnode.

Returns:

an appropriate return value (usually, the object built using subNodeResult) if the visit should continue, or null.

visitPre

public boolean visitPre(Remap node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Remap node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(Remap node,
                                  DocumentIterator subNode)

Description copied from interface: QueryBuilderVisitor

Visits a Remap node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the of result returned by the sole subnode.

Returns:

an appropriate return value (usually, the object built using subNodeResult) if the visit should continue, or null.

visitPre

public boolean visitPre(Weight node)
                 throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits a Weight node before recursing into the corresponding subtree.

Specified by:

visitPre in interface QueryBuilderVisitor<DocumentIterator>

Overrides:

visitPre in class AbstractQueryBuilderVisitor<DocumentIterator>

Parameters:

node - the node to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visitPost

public DocumentIterator visitPost(Weight node,
                                  DocumentIterator subNode)

Description copied from interface: QueryBuilderVisitor

Visits a Weight node after recursing into the corresponding subtree.

Parameters:

node - the internal node to be visited.

subNode - the of result returned by the sole subnode.

Returns:

an appropriate return value (usually, the object built using subNodeResult) if the visit should continue, or null.

visit

public DocumentIterator visit(True node)
                       throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits True.

Parameters:

node - the leaf to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException

visit

public DocumentIterator visit(False node)
                       throws QueryBuilderVisitorException

Description copied from interface: QueryBuilderVisitor

Visits False.

Parameters:

node - the leaf to be visited.

Returns:

true if the visit should continue.

Throws:

QueryBuilderVisitorException