com.bigdata.rdf.sparql.ast.eval

Class DataSetSummary

java.lang.Object

com.bigdata.rdf.sparql.ast.eval.DataSetSummary

public class DataSetSummary
extends Object

Helper class summarizes the named graphs or default graph mode for a quads query.

Field Summary

Fields

Modifier and Type	Field and Description
IV	firstContext The IV for the first graph having a known IV and IRawTripleStore#NULL if no graphs were specified having a known IV.
Set<IV>	graphs The set of graphs.
int	nknown The #of graphs in graphs whose term identifier is known.
int	nunknown The #of graphs in graphs whose term identifier is not known.

Constructor Summary

Constructors

Constructor and Description
DataSetSummary(Set<IV> graphs, boolean update)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	equals(Object o)
SubqueryCostReport	estimateSubqueryCost(BOpContextBase context, int limit, Predicate pred) Estimate cost of SUBQUERY with C bound (sampling).
Set<IV>	getGraphs() Return the distinct IVs for the graphs known to the database.
static Set<IV>	toInternalValues(Set<org.openrdf.model.URI> graphs)
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

graphs

public final Set<IV> graphs

The set of graphs. The URIs MUST have been resolved against the appropriate LexiconRelation such that their term identifiers (when the exist) are known. If any term identifier is IRawTripleStore#NULL, then the corresponding graph does not exist and no access path will be queried for that graph. However, a non- IRawTripleStore#NULL term identifier may also identify a graph which does not exist, in which case an access path will be created for that URIs but will not visit any data.

nknown

public final int nknown

The #of graphs in graphs whose term identifier is known. While this is not proof that there is data in the quad store for a graph having the corresponding URI, it does allow the possibility that a graph could exist for that URI.

nunknown

public final int nunknown

The #of graphs in graphs whose term identifier is not known. For QUERY, this is proof that there is no data in the quad store for a graph having the corresponding URI. However, for UPDATE it is possible that a graph could be created for that URI during an UPDATE operation.

firstContext

public final IV firstContext

The IV for the first graph having a known IV and IRawTripleStore#NULL if no graphs were specified having a known IV.

Constructor Detail

DataSetSummary

public DataSetSummary(Set<IV> graphs,
              boolean update)

Parameters:

graphs - The set of named graphs in the SPARQL DATASET (optional). A runtime exception will be thrown during evaluation of the if the URIs are not BigdataURIs. If graphs := null, then the set of named graphs is understood to be ALL graphs in the quad store.

update - When true, unknown IVs WILL NOT be pruned from the DataSetSummary. This is because those graphs might be implicitly created during an UPDATE operation.

Method Detail

toInternalValues

public static Set<IV> toInternalValues(Set<org.openrdf.model.URI> graphs)

getGraphs

public Set<IV> getGraphs()

Return the distinct IVs for the graphs known to the database.

Returns:

An ordered set of the distinct IVs.

estimateSubqueryCost

public SubqueryCostReport estimateSubqueryCost(BOpContextBase context,
                                      int limit,
                                      Predicate pred)

Estimate cost of SUBQUERY with C bound (sampling).

Parameters:

context -

limit - The maximum #of samples to take.

pred - The predicate.

Returns:

The estimated cost report. This is adjusted based on the sample size and the #of graphs against which the query was issued and represents the total expected cost of the subqueries against all of the graphs in the Dataset.

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object