org.eclipse.rdf4j.federated.util

Class QueryStringUtil

java.lang.Object

org.eclipse.rdf4j.federated.util.QueryStringUtil

public class QueryStringUtil
extends Object

Various static functions for query handling and parsing.

Author:

Andreas Schwarte

Field Summary

Fields

Modifier and Type	Field and Description
static IRI	BNODE_URI A dummy URI which is used as a replacement for BNodes in appendBNode(StringBuilder, BNode) since BNodes cannot be expressed in SPARQL queries

Constructor Summary

Constructors

Constructor and Description
QueryStringUtil()

Method Summary

Modifier and Type	Method and Description
protected static StringBuilder	appendBNode(StringBuilder sb, BNode bNode) Append a dummy string (see BNODE_URI) to represent the BNode.
protected static StringBuilder	appendLiteral(StringBuilder sb, Literal lit) Append the literal to the stringbuilder.
protected static StringBuilder	appendURI(StringBuilder sb, IRI uri) Append the uri to the stringbuilder, i.e.
protected static StringBuilder	appendValue(StringBuilder sb, Value value) Append a string representation of the value to the string builder.
protected static StringBuilder	appendVar(StringBuilder sb, Var var, Set<String> varNames, BindingSet bindings) Append the variable to the provided StringBuilder.
protected static StringBuilder	appendVarId(StringBuilder sb, Var var, String varID, Set<String> varNames, BindingSet bindings) Append the variable to the provided StringBuilder, however change name of variable by appending "_varId" to it.
static String	askQueryString(ExclusiveTupleExpr expr, BindingSet bindings) Transform the ExclusiveTupleExpr into a ASK query string
static String	askQueryString(StatementPattern stmt, BindingSet bindings) Construct a boolean ASK query for the provided statement.
protected static String	constructInnerUnion(StatementPattern stmt, int outerID, Set<String> varNames, List<BindingSet> bindings)
protected static String	constructJoinArg(ExclusiveTupleExpr exclusiveExpr, Set<String> varNames, BindingSet bindings) Construct a query substring from the ExclusiveTupleExpr that can be used as an argument to a Join.
protected static String	constructStatement(StatementPattern stmt, Set<String> varNames, BindingSet bindings) Construct the statement string, i.e.
protected static String	constructStatementCheckId(StatementPattern stmt, int varID, Set<String> varNames, BindingSet bindings) Construct the statement string, i.e.
protected static String	constructStatementId(StatementPattern stmt, String varID, Set<String> varNames, BindingSet bindings) Construct the statement string, i.e.
protected static String	getValueString(Value value) Return the string representation of this value, see appendValue(StringBuilder, Value) for details.
static boolean	hasFreeVars(StatementPattern stmt, BindingSet bindings) returns true iff there is at least one free variable, i.e.
static List<String>	loadQueries(String queryFile) load the queries from a queries file located at the specified path.
static String	selectQueryString(ExclusiveGroup group, BindingSet bindings, FilterValueExpr filterExpr, AtomicBoolean evaluated) Construct a SELECT query for the provided ExclusiveGroup.
static String	selectQueryString(ExclusiveTupleExprRenderer expr, BindingSet bindings, FilterValueExpr filterExpr, AtomicBoolean evaluated) Construct a SELECT query for the provided ExclusiveTupleExprRenderer
static String	selectQueryString(FedXStatementPattern stmt, BindingSet bindings, FilterValueExpr filterExpr, AtomicBoolean evaluated) Construct a SELECT query for the provided statement.
static String	selectQueryStringBoundCheck(StatementPattern stmt, List<BindingSet> unionBindings) Construct a SELECT query for a grouped bound check.
static String	selectQueryStringBoundJoinVALUES(StatementPattern stmt, List<BindingSet> unionBindings, FilterValueExpr filterExpr, AtomicBoolean evaluated) Creates a bound join subquery using the SPARQL 1.1 VALUES operator.
static String	selectQueryStringBoundUnion(StatementPattern stmt, List<BindingSet> unionBindings, FilterValueExpr filterExpr, Boolean evaluated) Deprecated. replaced with selectQueryStringBoundJoinVALUES(StatementPattern, List, FilterValueExpr, AtomicBoolean)
static String	selectQueryStringLimit1(ExclusiveGroup group, BindingSet bindings) Construct a SELECT query for the provided ExclusiveGroup with LIMIT 1.
static String	selectQueryStringLimit1(ExclusiveTupleExpr expr, BindingSet bindings) Construct a SELECT query for the provided expr with LIMIT 1.
static String	selectQueryStringLimit1(StatementPattern stmt, BindingSet bindings) Construct a SELECT query for the provided statement with LIMIT 1.
static String	toString(ArbitraryLengthPath node, Set<String> varNames, BindingSet bindings) Converts an ArbitraryLengthPath node to a sub query string and makes sure to insert any bindings.
static String	toString(Resource subj, IRI pred, Value obj) Return a string representation of this statement using the following pattern, where variables are indicated using ?var and values are represented as strings.
static String	toString(StatementPattern stmt) Return a string representation of this statement using the following pattern, where variables are indicated using ?var and values are represented as strings.
static String	toString(Var var)

Methods inherited from class java.lang.Object

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

Field Detail

BNODE_URI

public static final IRI BNODE_URI

A dummy URI which is used as a replacement for BNodes in appendBNode(StringBuilder, BNode) since BNodes cannot be expressed in SPARQL queries

Constructor Detail

QueryStringUtil

public QueryStringUtil()

Method Detail

hasFreeVars

public static boolean hasFreeVars(StatementPattern stmt,
                                  BindingSet bindings)

returns true iff there is at least one free variable, i.e. there is no binding for any variable

Parameters:

stmt -

bindings -

Returns:

whether free vars are available

toString

public static String toString(StatementPattern stmt)

Return a string representation of this statement using the following pattern, where variables are indicated using ?var and values are represented as strings. Pattern: {s; p; o}

Parameters:

stmt -

Returns:

a string representation of the statement

toString

public static String toString(ArbitraryLengthPath node,
                              Set<String> varNames,
                              BindingSet bindings)

Converts an ArbitraryLengthPath node to a sub query string and makes sure to insert any bindings.

This method assumes that the ArbitraryLengthPath.getPathExpression() is a StatementPattern.

Parameters:

node -

varNames -

bindings -

Returns:

the query string

toString

public static String toString(Var var)

toString

public static String toString(Resource subj,
                              IRI pred,
                              Value obj)

Return a string representation of this statement using the following pattern, where variables are indicated using ?var and values are represented as strings. Pattern: {s; p; o}

Parameters:

subj - the subject

pred - the predicate

obj - the object

Returns:

a string representation

selectQueryString

public static String selectQueryString(FedXStatementPattern stmt,
                                       BindingSet bindings,
                                       FilterValueExpr filterExpr,
                                       AtomicBoolean evaluated)
                                throws IllegalQueryException

Construct a SELECT query for the provided statement.

Parameters:

stmt -

bindings -

filterExpr -

evaluated - parameter can be used outside this method to check whether FILTER has been evaluated, false in beginning

Returns:

the SELECT query

Throws:

IllegalQueryException - if the query does not have any free variables

selectQueryString

public static String selectQueryString(ExclusiveTupleExprRenderer expr,
                                       BindingSet bindings,
                                       FilterValueExpr filterExpr,
                                       AtomicBoolean evaluated)
                                throws IllegalQueryException

Construct a SELECT query for the provided ExclusiveTupleExprRenderer

Parameters:

stmt -

bindings -

filterExpr -

evaluated - parameter can be used outside this method to check whether FILTER has been evaluated, false in beginning

Returns:

the SELECT query

Throws:

IllegalQueryException - if the query does not have any free variables

selectQueryString

public static String selectQueryString(ExclusiveGroup group,
                                       BindingSet bindings,
                                       FilterValueExpr filterExpr,
                                       AtomicBoolean evaluated)
                                throws IllegalQueryException

Construct a SELECT query for the provided ExclusiveGroup. Note that bindings and filterExpr are applied whenever possible.

Parameters:

group - the expression for the query

bindings - the bindings to be applied

filterExpr - a filter expression or null

evaluated - parameter can be used outside this method to check whether FILTER has been evaluated, false in beginning

Returns:

the SELECT query string

Throws:

IllegalQueryException

askQueryString

public static String askQueryString(ExclusiveTupleExpr expr,
                                    BindingSet bindings)

Transform the ExclusiveTupleExpr into a ASK query string

Parameters:

expr -

bindings -

Returns:

the ASK query string

Throws:

IllegalQueryException

selectQueryStringBoundUnion

@Deprecated
public static String selectQueryStringBoundUnion(StatementPattern stmt,
                                                             List<BindingSet> unionBindings,
                                                             FilterValueExpr filterExpr,
                                                             Boolean evaluated)

Deprecated. replaced with selectQueryStringBoundJoinVALUES(StatementPattern, List, FilterValueExpr, AtomicBoolean)

Construct a SELECT query string for a bound union. Pattern: SELECT ?v_1 ?v_2 ?v_N WHERE { { ?v_1 p o } UNION { ?v_2 p o } UNION ... } Note that the filterExpr is not evaluated at the moment.

Parameters:

stmt -

unionBindings -

filterExpr -

evaluated - parameter can be used outside this method to check whether FILTER has been evaluated, false in beginning

Returns:

the SELECT query string

selectQueryStringBoundJoinVALUES

public static String selectQueryStringBoundJoinVALUES(StatementPattern stmt,
                                                      List<BindingSet> unionBindings,
                                                      FilterValueExpr filterExpr,
                                                      AtomicBoolean evaluated)

Creates a bound join subquery using the SPARQL 1.1 VALUES operator.

Example subquery:

 SELECT ?v ?__index WHERE { 
    VALUES (?s ?__index) { 
      (:s1 1) (:s2 2) 
      ... 
      (:sN N) 
    } 
    ?s name ?v. 
 }
 

Parameters:

stmt -

unionBindings -

filterExpr -

evaluated - parameter can be used outside this method to check whether FILTER has been evaluated, false in beginning

Returns:

the SELECT query string

Since:

3.0

See Also:

SparqlFederationEvalStrategy, BoundJoinVALUESConversionIteration

selectQueryStringBoundCheck

public static String selectQueryStringBoundCheck(StatementPattern stmt,
                                                 List<BindingSet> unionBindings)

Construct a SELECT query for a grouped bound check. Pattern: SELECT ?o_1 .. ?o_N WHERE { { s1 p1 ?o_1 FILTER ?o_1=o1 } UNION ... UNION { sN pN ?o_N FILTER ?o_N=oN }}

Parameters:

stmt -

unionBindings -

Returns:

the SELECT query string

constructInnerUnion

protected static String constructInnerUnion(StatementPattern stmt,
                                            int outerID,
                                            Set<String> varNames,
                                            List<BindingSet> bindings)

constructJoinArg

protected static String constructJoinArg(ExclusiveTupleExpr exclusiveExpr,
                                         Set<String> varNames,
                                         BindingSet bindings)

Construct a query substring from the ExclusiveTupleExpr that can be used as an argument to a Join.

This method can only be used for ExclusiveTupleExpr that additionally provide ExclusiveTupleExprRenderer capabilities. An exception to this is if the given expression is a StatementPattern, e.g. an ExclusiveStatement or ExclusiveGroup.

Parameters:

exclusiveExpr -

varNames -

bindings -

Returns:

the query string with bindings inserted

askQueryString

public static String askQueryString(StatementPattern stmt,
                                    BindingSet bindings)

Construct a boolean ASK query for the provided statement.

Parameters:

stmt -

bindings -

Returns:

the ASK query string

selectQueryStringLimit1

public static String selectQueryStringLimit1(StatementPattern stmt,
                                             BindingSet bindings)

Construct a SELECT query for the provided statement with LIMIT 1. Such query can be used for source selection instead of ASK queries.

Parameters:

stmt -

bindings -

Returns:

the SELECT query string

selectQueryStringLimit1

public static String selectQueryStringLimit1(ExclusiveTupleExpr expr,
                                             BindingSet bindings)

Construct a SELECT query for the provided expr with LIMIT 1. Such query can be used for source selection instead of ASK queries.

Parameters:

stmt -

bindings -

Returns:

the SELECT query string

selectQueryStringLimit1

public static String selectQueryStringLimit1(ExclusiveGroup group,
                                             BindingSet bindings)

Construct a SELECT query for the provided ExclusiveGroup with LIMIT 1. Such query can be used for source selection instead of ASK queries.

Parameters:

group -

bindings -

Returns:

the SELECT query string

constructStatement

protected static String constructStatement(StatementPattern stmt,
                                           Set<String> varNames,
                                           BindingSet bindings)

Construct the statement string, i.e. "s p o . " with bindings inserted wherever possible. Note that the relevant free variables are added to the varNames set for further evaluation.

Parameters:

stmt -

varNames -

bindings -

Returns:

the constructed statement pattern

constructStatementId

protected static String constructStatementId(StatementPattern stmt,
                                             String varID,
                                             Set<String> varNames,
                                             BindingSet bindings)

Construct the statement string, i.e. "s p o . " with bindings inserted wherever possible. Variables are renamed to "var_"+varId to identify query results in bound queries. Note that the free variables are also added to the varNames set for further evaluation.

Parameters:

stmt -

varNames -

bindings -

Returns:

the constructed statement pattern

constructStatementCheckId

protected static String constructStatementCheckId(StatementPattern stmt,
                                                  int varID,
                                                  Set<String> varNames,
                                                  BindingSet bindings)

Construct the statement string, i.e. "s p ?o_varID FILTER ?o_N=o ". This kind of statement pattern is necessary to later on identify available results.

Parameters:

stmt -

varID -

varNames -

bindings -

Returns:

the statement pattern string

appendVar

protected static StringBuilder appendVar(StringBuilder sb,
                                         Var var,
                                         Set<String> varNames,
                                         BindingSet bindings)

Append the variable to the provided StringBuilder. Cases: 1) unbound: check provided bindingset for possible match a) match found: append matching value b) no match: append ?varName and add to varNames 2) bound: append value

Parameters:

sb -

var -

varNames -

bindings -

Returns:

the stringbuilder

appendVarId

protected static StringBuilder appendVarId(StringBuilder sb,
                                           Var var,
                                           String varID,
                                           Set<String> varNames,
                                           BindingSet bindings)

Append the variable to the provided StringBuilder, however change name of variable by appending "_varId" to it. Cases: 1) unbound: check provided bindingset for possible match a) match found: append matching value b) no match: append ?varName_varId and add to varNames 2) bound: append value

Parameters:

sb -

var -

varNames -

bindings -

Returns:

the complemented string builder

getValueString

protected static String getValueString(Value value)

Return the string representation of this value, see appendValue(StringBuilder, Value) for details.

Parameters:

value -

Returns:

the string representation

appendValue

protected static StringBuilder appendValue(StringBuilder sb,
                                           Value value)

Append a string representation of the value to the string builder. 1. URI: 2. Literal: "myLiteral"^^

Parameters:

sb -

value -

Returns:

the string builder

appendURI

protected static StringBuilder appendURI(StringBuilder sb,
                                         IRI uri)

Append the uri to the stringbuilder, i.e. .

Parameters:

sb -

uri -

Returns:

the string builder

appendBNode

protected static StringBuilder appendBNode(StringBuilder sb,
                                           BNode bNode)

Append a dummy string (see BNODE_URI) to represent the BNode. Note: currently it is not possible to retrieve values for a BNode via SPARQL, hence we use a dummy BNode which does not produce any results. A warning is printed to debug.

Parameters:

sb -

bNode -

Returns:

the string builder

appendLiteral

protected static StringBuilder appendLiteral(StringBuilder sb,
                                             Literal lit)

Append the literal to the stringbuilder.

Parameters:

sb -

lit -

Returns:

the string builder

loadQueries

public static List<String> loadQueries(String queryFile)
                                throws FileNotFoundException,
                                       IOException

load the queries from a queries file located at the specified path. Expected format: - Queries are SPARQL queries in String format - queries are allowed to span several lines - a query is interpreted to be finished if an empty line occurs Ex: QUERY1 ... Q1 cntd QUERY2

Parameters:

queryFile -

Returns:

a list of queries for the query type

Throws:

FileNotFoundException

IOException