/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.sparql.lang;
import java.util.* ;
import org.apache.jena.query.ARQ ;
import org.apache.jena.query.Query ;
import org.apache.jena.query.QueryParseException ;
import org.apache.jena.query.Syntax ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.core.VarExprList ;
import org.apache.jena.sparql.expr.Expr ;
import org.apache.jena.sparql.syntax.* ;
/** Calculate in-scope variables from the AST */
public class SyntaxVarScope
{
/* SPARQL 1.1 "in scope" rules
These define the variables from a pattern that are in-scope
These are not the usage rules.
Syntax Form In-scope variables
Basic Graph Pattern (BGP) v occurs in the BGP
Path v occurs in the path
Group { P1 P2 ... } v is in-scope if in-scope in one or more of P1, P2, ...
GRAPH term { P } v is term or v is in-scope in P
{ P1 } UNION { P2 } v is in-scope in P1 or in-scope in P2
OPTIONAL {P} v is in-scope in P
SERVICE term {P} v is term or v is in-scope in P
(expr AS v) for BIND, SELECT and GROUP BY v is in-scope
SELECT ..v .. { P } v is in-scope if v is mentioned as a project variable
SELECT * { P } v is in-scope in P
VALUES var (values) v is in-scope if v is in varlist
VALUES varlist (values) v is in-scope if v is in varlist
*/
// Weakness : EXISTS inside FILTERs?
public static void check(Query query)
{
if ( query.getQueryPattern() == null )
// DESCRIBE may not have a pattern
return ;
check(query.getQueryPattern()) ;
// Check this level.
checkQueryScope(query) ;
// Other checks.
Collection<Var> vars = varsOfQuery(query) ;
check(query, vars) ;
}
public static void check(Element queryPattern) {
checkSubQuery(queryPattern) ;
checkBind(queryPattern);
}
// Check BIND by accumulating variables and making sure BIND does not attempt to reuse one
private static void checkBind(Element queryPattern)
{
BindScopeChecker v = new BindScopeChecker() ;
ElementWalker.walk(queryPattern, v) ;
}
// Check subquery by finding subquries and recurisively checking.
// Includes appling all checks to nested subqueries.
private static void checkSubQuery(Element el)
{
ElementVisitor v = new SubQueryScopeChecker() ;
ElementWalker.walk(el, v) ;
}
// Check one level of query - SELECT expressions
private static void checkQueryScope(Query query)
{
Collection<Var> vars = varsOfQuery(query) ;
checkExprListAssignment(vars, query.getProject()) ;
}
// get all vars of a query
private static Collection<Var> varsOfQuery(Query query)
{
Collection<Var> vars = PatternVars.vars(query.getQueryPattern()) ;
if ( query.hasValues() )
vars.addAll(query.getValuesVariables()) ;
return vars ;
}
// Other check (not scoping at this level) of a query
private static void check(Query query, Collection<Var> vars)
{
// Check any expressions are assigned to fresh variables.
checkExprListAssignment(vars, query.getProject()) ;
// Check for SELECT * GROUP BY
// Legal in ARQ, not in SPARQL 1.1
if ( ! Syntax.syntaxARQ.equals(query.getSyntax()) )
{
if ( query.isQueryResultStar() && query.hasGroupBy() )
throw new QueryParseException("SELECT * not legal with GROUP BY", -1 , -1) ;
}
// Check any variable in an expression is in scope (if GROUP BY)
checkExprVarUse(query) ;
// Check GROUP BY AS
// ENABLE
if ( false && query.hasGroupBy() )
{
VarExprList exprList2 = query.getGroupBy() ;
checkExprListAssignment(vars, exprList2) ;
// CHECK
}
}
private static void checkExprListAssignment(Collection<Var> vars, VarExprList exprList)
{
Set<Var> vars2 = new LinkedHashSet<>(vars) ;
exprList.forEachExpr((v,e) -> {
Set<Var> varInExpr = e.getVarsMentioned() ;
// Include mentioned variables
// These may be unused in the query (in vars) but stil contribute.
vars2.addAll(varInExpr) ;
checkAssignment( vars2, e, v );
vars2.add( v );
}) ;
}
private static void checkExprVarUse(Query query)
{
if ( query.hasGroupBy() )
{
VarExprList groupKey = query.getGroupBy() ;
// Copy - we need to add variables
// SELECT (count(*) AS ?C) (?C+1 as ?D)
List<Var> inScopeVars = new ArrayList<>(groupKey.getVars()) ;
VarExprList exprList = query.getProject() ;
for ( Var v : exprList.getVars() )
{
// In scope?
Expr e = exprList.getExpr( v );
if ( e == null )
{
if ( !inScopeVars.contains( v ) )
{
throw new QueryParseException( "Non-group key variable in SELECT: " + v, -1, -1 );
}
}
else
{
Set<Var> eVars = e.getVarsMentioned();
for ( Var v2 : eVars )
{
if ( !inScopeVars.contains( v2 ) )
{
throw new QueryParseException(
"Non-group key variable in SELECT: " + v2 + " in expression " + e, -1, -1 );
}
}
}
inScopeVars.add( v );
}
}
}
private static void checkAssignment(Collection<Var> scope, Expr expr, Var var)
{
// Project SELECT ?x
if ( expr == null )
return ;
// expr not null
if ( scope.contains(var) )
throw new QueryParseException("Variable used when already in-scope: "+var+" in "+fmtAssignment(expr, var), -1 , -1) ;
// test for impossible variables - bound() is a bit odd.
if ( false )
{
Set<Var> vars = expr.getVarsMentioned() ;
for ( Var v : vars )
{
if ( !scope.contains(v) )
throw new QueryParseException("Variable used in expression is not in-scope: "+v+" in "+expr, -1 , -1) ;
}
}
}
private static String fmtExprList(VarExprList exprList)
{
StringBuilder sb = new StringBuilder() ;
boolean first = true ;
for ( Var v : exprList.getVars() )
{
Expr e = exprList.getExpr( v );
if ( !first )
{
sb.append( " " );
}
first = false;
sb.append( "(" ).append( e ).append( " AS " ).append( v ).append( ")" );
}
return sb.toString() ;
}
private static String fmtAssignment(Expr expr, Var var)
{
return "("+expr+" AS "+var+")" ;
}
// Modifed walked for variables.
/** Visitor for subqueries scope rules . */
private static class SubQueryScopeChecker extends ElementVisitorBase
{
@Override
public void visit(ElementSubQuery el)
{
Query query = el.getQuery() ;
checkQueryScope(query) ;
// Recursively check sub-queries in sub-queries.
check(el.getQuery()) ;
}
}
// Applies scope rules at each point it matters.
// Does some recalculation in nested structures.
public static class BindScopeChecker extends ElementVisitorBase
{
public BindScopeChecker() {}
@Override
public void visit(ElementGroup el)
{
// BIND scope rules
// (and service warning)
for ( int i = 0 ; i < el.size() ; i++ )
{
Element e = el.get(i) ;
// Tests.
if ( e instanceof ElementBind )
{
Collection<Var> accScope = calcScopeAll(el.getElements(), i) ;
check(accScope, (ElementBind)e) ;
}
if ( e instanceof ElementService )
{
Collection<Var> accScope = calcScopeAll(el.getElements(), i) ;
check(accScope, (ElementService)e) ;
}
}
}
private static Collection<Var> calcScopeAll(List<Element> elements, int idx)
{
return calcScope(elements, 0, idx) ;
}
/** Calculate scope, working forwards */
private static Collection<Var> calcScope(List<Element> elements, int start, int finish)
{
Collection<Var> accScope = new HashSet<>() ;
for ( int i = start ; i < finish ; i++ )
{
Element e = elements.get(i) ;
PatternVars.vars(accScope, e) ;
}
return accScope ;
}
// Inside filters.
private static void check(Collection<Var> scope, ElementBind el)
{
Var var = el.getVar() ;
if ( scope.contains(var) )
throw new QueryParseException("BIND: Variable used when already in-scope: "+var+" in "+el, -1 , -1) ;
checkAssignment(scope, el.getExpr(), var) ;
}
private static void check(Collection<Var> scope, ElementService el)
{
if ( ARQ.isStrictMode() && el.getServiceNode().isVariable() )
{
Var var = Var.alloc(el.getServiceNode()) ;
if ( ! scope.contains(var) )
throw new QueryParseException("SERVICE: Variable not already in-scope: "+var+" in "+el, -1 , -1) ;
}
}
}
}