/*
* eXist Open Source Native XML Database
* Copyright (C) 2001-04, Wolfgang M. Meier (meier@ifs.tu-darmstadt.de)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* $Id$
*/
package org.exist.xquery;
import org.exist.dom.ContextItem;
import org.exist.dom.DocumentImpl;
import org.exist.dom.DocumentSet;
import org.exist.dom.NewArrayNodeSet;
import org.exist.dom.NodeProxy;
import org.exist.dom.NodeSet;
import org.exist.dom.VirtualNodeSet;
import org.exist.xquery.util.ExpressionDumper;
import org.exist.xquery.value.Item;
import org.exist.xquery.value.NumericValue;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceIterator;
import org.exist.xquery.value.Type;
import org.exist.xquery.value.ValueSequence;
import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;
/**
* Handles predicate expressions.
*
*@author Wolfgang Meier
*/
public class Predicate extends PathExpr {
public final static int UNKNOWN = -1;
public final static int NODE = 0;
public final static int BOOLEAN = 1;
public final static int POSITIONAL = 2;
private CachedResult cached = null;
private int executionMode = UNKNOWN;
private int outerContextId;
private Expression parent;
public Predicate(XQueryContext context) {
super(context);
}
/* (non-Javadoc)
* @see org.exist.xquery.PathExpr#getDependencies()
*/
public int getDependencies() {
int deps = 0;
if(getLength() == 1) {
deps = getExpression(0).getDependencies();
} else {
deps = super.getDependencies();
}
return deps;
}
/* (non-Javadoc)
* @see org.exist.xquery.PathExpr#analyze(org.exist.xquery.AnalyzeContextInfo)
*/
public void analyze(AnalyzeContextInfo contextInfo) throws XPathException {
parent = contextInfo.getParent();
AnalyzeContextInfo newContextInfo = createContext(contextInfo);
super.analyze(newContextInfo);
Expression inner = getExpression(0);
final int staticReturnType = newContextInfo.getStaticReturnType();
final int innerType = staticReturnType != Type.ITEM ?
staticReturnType : inner.returnsType();
// Case 1: predicate expression returns a node set.
// Check the returned node set against the context set
// and return all nodes from the context, for which the
// predicate expression returns a non-empty sequence.
if (Type.subTypeOf(innerType, Type.NODE) && !Dependency.dependsOn(inner, Dependency.CONTEXT_ITEM)) {
executionMode = NODE;
// Case 2: predicate expression returns a unique number and has no dependency with the context item.
} else if (Type.subTypeOf(innerType, Type.NUMBER) && !Dependency.dependsOn(inner, Dependency.CONTEXT_ITEM)
&& Cardinality.checkCardinality(inner.getCardinality(), Cardinality.EXACTLY_ONE))
executionMode = POSITIONAL;
// Case 3: all other cases, boolean evaluation (that can be "promoted" later)
else
executionMode = BOOLEAN;
if(executionMode == BOOLEAN) {
// need to re-analyze:
newContextInfo = createContext(contextInfo);
newContextInfo.addFlag(SINGLE_STEP_EXECUTION);
super.analyze(newContextInfo);
}
if (executionMode == POSITIONAL && staticReturnType != Type.ITEM && !Dependency.dependsOn(inner, Dependency.CONTEXT_ITEM)) {
contextInfo.addFlag(POSITIONAL_PREDICATE);
}
}
private AnalyzeContextInfo createContext(AnalyzeContextInfo contextInfo) {
AnalyzeContextInfo newContextInfo = new AnalyzeContextInfo(contextInfo);
newContextInfo.addFlag(IN_PREDICATE); // set flag to signal subexpression that we are in a predicate
newContextInfo.removeFlag(IN_WHERE_CLAUSE); // remove where clause flag
newContextInfo.removeFlag(DOT_TEST);
outerContextId = newContextInfo.getContextId();
newContextInfo.setContextId(getExpressionId());
newContextInfo.setStaticType(contextInfo.getStaticType());
newContextInfo.setParent(this);
return newContextInfo;
}
public Sequence preprocess() throws XPathException {
Expression inner = steps.size() == 1 ? getExpression(0) : this;
return inner.eval(null);
}
public Sequence evalPredicate(Sequence outerSequence, Sequence contextSequence, int mode)
throws XPathException {
if (context.getProfiler().isEnabled()) {
context.getProfiler().start(this);
context.getProfiler().message(this, Profiler.DEPENDENCIES, "DEPENDENCIES", Dependency.getDependenciesName(this.getDependencies()));
if (contextSequence != null)
context.getProfiler().message(this, Profiler.START_SEQUENCES, "CONTEXT SEQUENCE", contextSequence);
}
Sequence result;
Expression inner = steps.size() == 1 ? getExpression(0) : this;
if (inner == null)
result = Sequence.EMPTY_SEQUENCE;
else {
if (executionMode == UNKNOWN)
executionMode = BOOLEAN;
int recomputedExecutionMode = executionMode;
Sequence innerSeq = null;
//Atomic context sequences :
if (Type.subTypeOf(contextSequence.getItemType(), Type.ATOMIC)) {
//We can't have a node set operation : reconsider depending of the inner sequence
if (executionMode == NODE && !(contextSequence instanceof VirtualNodeSet)) {
//(1,2,2,4)[.]
if (Type.subTypeOf(contextSequence.getItemType(), Type.NUMBER)) {
recomputedExecutionMode = POSITIONAL;
} else {
recomputedExecutionMode = BOOLEAN;
}
}
//If there is no dependency on the context item, try a positional promotion
if (executionMode == BOOLEAN && !Dependency.dependsOn(inner, Dependency.CONTEXT_ITEM)
//Hack : GeneralComparison lies on its dependencies
//TODO : try to remove this since our dependency computation should now be better
&& !((inner instanceof GeneralComparison) && ((GeneralComparison)inner).invalidNodeEvaluation)) {
innerSeq = inner.eval(contextSequence);
//Only if we have an actual *singleton* of numeric items
if (innerSeq.hasOne() && Type.subTypeOf(innerSeq.getItemType(), Type.NUMBER)) {
recomputedExecutionMode = POSITIONAL;
}
}
} else if (executionMode == NODE && !contextSequence.isPersistentSet()) {
recomputedExecutionMode = BOOLEAN;
} else {
if (executionMode == BOOLEAN && !Dependency.dependsOn(inner, Dependency.CONTEXT_ITEM)) {
/*
*
* WARNING : this sequence will be evaluated with preloadable nodesets !
*
*/
innerSeq = inner.eval(contextSequence);
//Try to promote a boolean evaluation to a nodeset one
//We are now sure of the inner sequence return type
if (Type.subTypeOf(innerSeq.getItemType(), Type.NODE) && innerSeq.isPersistentSet()) {
recomputedExecutionMode = NODE;
//Try to promote a boolean evaluation to a positional one
//Only if we have an actual *singleton* of numeric items
} else if (innerSeq.hasOne() && Type.subTypeOf(innerSeq.getItemType(), Type.NUMBER)) {
recomputedExecutionMode = POSITIONAL;
}
}
}
switch(recomputedExecutionMode) {
case NODE:
if (context.getProfiler().isEnabled())
context.getProfiler().message(this, Profiler.OPTIMIZATION_FLAGS,
"OPTIMIZATION CHOICE", "Node selection");
result = selectByNodeSet(contextSequence);
break;
case BOOLEAN:
if (context.getProfiler().isEnabled())
context.getProfiler().message(this, Profiler.OPTIMIZATION_FLAGS,
"OPTIMIZATION CHOICE", "Boolean evaluation");
result = evalBoolean(contextSequence, inner);
break;
case POSITIONAL:
if (context.getProfiler().isEnabled())
context.getProfiler().message(this, Profiler.OPTIMIZATION_FLAGS,
"OPTIMIZATION CHOICE", "Positional evaluation");
//In case it hasn't been evaluated above
if (innerSeq == null) {
innerSeq = inner.eval(contextSequence);
}
result = selectByPosition(outerSequence, contextSequence, mode, innerSeq);
break;
default:
throw new IllegalArgumentException("Unsupported execution mode: '" + recomputedExecutionMode + "'");
}
}
if (context.getProfiler().isEnabled())
context.getProfiler().end(this, "", result);
return result;
}
/**
* @param contextSequence
* @param inner
* @return The result of the boolean evaluation of the predicate.
* @throws XPathException
*/
private Sequence evalBoolean(Sequence contextSequence, Expression inner) throws XPathException {
Sequence result = new ValueSequence();
int p;
if (contextSequence instanceof NodeSet && ((NodeSet)contextSequence).getProcessInReverseOrder()) {
//This one may be expensive...
p = contextSequence.getItemCount();
for (SequenceIterator i = contextSequence.iterate(); i.hasNext(); p--) {
//0-based
context.setContextPosition(p - 1);
Item item = i.nextItem();
Sequence innerSeq = inner.eval(contextSequence, item);
if(innerSeq.effectiveBooleanValue())
result.add(item);
}
} else {
//0-based
p = 0;
//TODO : is this block also accurate in reverse-order processing ?
//Compute each position in the boolean-like way...
//... but grab some context positions ! -<8-P
if (Type.subTypeOf(inner.returnsType(), Type.NUMBER) && Dependency.dependsOn(inner, Dependency.CONTEXT_ITEM)) {
Set positions = new TreeSet();
for (SequenceIterator i = contextSequence.iterate(); i.hasNext(); p++) {
context.setContextPosition(p);
Item item = i.nextItem();
Sequence innerSeq = inner.eval(contextSequence, item);
//TODO : introduce a check in innerSeq.hasOne() ?
NumericValue nv = (NumericValue)innerSeq.itemAt(0);
//Non integers return... nothing, not even an error !
if (!nv.hasFractionalPart() && !nv.isZero())
positions.add(nv);
}
for (Iterator i = positions.iterator() ; i.hasNext() ;) {
int position = ((NumericValue)i.next()).getInt();
//TODO : move this test above ?
if (position <= contextSequence.getItemCount())
result.add(contextSequence.itemAt(position - 1));
}
} else {
Set positions = new TreeSet();
for (SequenceIterator i = contextSequence.iterate(); i.hasNext(); p++) {
context.setContextPosition(p);
Item item = i.nextItem();
Sequence innerSeq = inner.eval(contextSequence, item);
if (innerSeq.hasOne() && Type.subTypeOf(innerSeq.getItemType(), Type.NUMBER)) {
//TODO : introduce a check in innerSeq.hasOne() ?
NumericValue nv = (NumericValue)innerSeq;
//Non integers return... nothing, not even an error !
if (!nv.hasFractionalPart() && !nv.isZero())
positions.add(nv);
} else if (innerSeq.effectiveBooleanValue())
result.add(item);
}
for (Iterator i = positions.iterator() ; i.hasNext() ;) {
int position = ((NumericValue)i.next()).getInt();
//TODO : move this test above ?
if (position <= contextSequence.getItemCount())
result.add(contextSequence.itemAt(position - 1));
}
}
}
return result;
}
/**
* @param contextSequence
* @return The result of the node set evaluation of the predicate.
* @throws XPathException
*/
private Sequence selectByNodeSet(Sequence contextSequence) throws XPathException {
NewArrayNodeSet result = new NewArrayNodeSet();
NodeSet contextSet = contextSequence.toNodeSet();
boolean contextIsVirtual = contextSet instanceof VirtualNodeSet;
/*
//Uncomment the lines below which are intended to work around a VirtualNodeSet bug
//No need to say that performance can suffer !
NodeSet nodes;
if (contextIsVirtual) {
ArraySet copy = new ArraySet(contextSet.getLength());
for (Iterator i = contextSet.iterator(); i.hasNext();) {
copy.add((Item)i.next());
}
nodes = super.eval(copy, null).toNodeSet();
} else
nodes = super.eval(contextSet, null).toNodeSet();
//End of work-around
*/
//Comment the line below if you have uncommented the lines above :-)
NodeSet nodes = super.eval(contextSet, null).toNodeSet();
/* if the predicate expression returns results from the cache
* we can also return the cached result.
*/
if(cached != null && cached.isValid(contextSequence, null) && nodes.isCached()) {
if (context.getProfiler().isEnabled())
context.getProfiler().message(this, Profiler.OPTIMIZATIONS,
"Using cached results", result);
return cached.getResult();
}
DocumentImpl lastDoc = null;
for (Iterator i = nodes.iterator(); i.hasNext();) {
NodeProxy currentNode = (NodeProxy) i.next();
int sizeHint = Constants.NO_SIZE_HINT;
if(lastDoc == null || currentNode.getDocument() != lastDoc) {
lastDoc = currentNode.getDocument();
sizeHint = nodes.getSizeHint(lastDoc);
}
ContextItem contextItem = currentNode.getContext();
if (contextItem == null) {
throw new XPathException(this, "Internal evaluation error: context is missing for node " +
currentNode.getNodeId() + " !");
}
//TODO : review to consider transverse context
while (contextItem != null) {
if (contextItem.getContextId() == getExpressionId()) {
NodeProxy next = contextItem.getNode();
if(contextIsVirtual || contextSet.contains(next)) {
next.addMatches(currentNode);
result.add(next, sizeHint);
}
}
contextItem = contextItem.getNextDirect();
}
}
if (contextSequence.isCacheable())
cached = new CachedResult(contextSequence, null, result);
return result;
}
/**
* @param outerSequence
* @param contextSequence
* @param mode
* @param innerSeq
* @return The result of the positional evaluation of the predicate.
* @throws XPathException
*/
private Sequence selectByPosition(Sequence outerSequence, Sequence contextSequence, int mode, Sequence innerSeq) throws XPathException {
if(outerSequence != null && !outerSequence.isEmpty() &&
Type.subTypeOf(contextSequence.getItemType(), Type.NODE) &&
contextSequence.isPersistentSet() &&
outerSequence.isPersistentSet()) {
Sequence result = new NewArrayNodeSet(100);
NodeSet contextSet = contextSequence.toNodeSet();
switch(mode) {
case Constants.CHILD_AXIS:
case Constants.ATTRIBUTE_AXIS:
case Constants.DESCENDANT_AXIS:
case Constants.DESCENDANT_SELF_AXIS:
case Constants.DESCENDANT_ATTRIBUTE_AXIS:
{
NodeSet outerNodeSet;
//Ugly and costly processing of VirtualNodeSets
//TODO : CORRECT THIS !!!
if (outerSequence instanceof VirtualNodeSet) {
// Looks like we don't need to treat VirtualNodeSet specially here.
outerNodeSet = outerSequence.toNodeSet();
// outerNodeSet = new NewArrayNodeSet();
// for (int i = 0 ; i < outerSequence.getItemCount() ; i++) {
// outerNodeSet.add(outerSequence.itemAt(i));
// }
} else outerNodeSet = outerSequence.toNodeSet();
//Comment the line below if you have uncommented the lines above :-)
//TODO: in some cases, especially with in-memory nodes,
//outerSequence.toNodeSet() will generate a document
//which will be different from the one(s) in contextSet
//ancestors will thus be empty :-(
// A special treatment of VirtualNodeSet does not seem to be required
// anymore, at least for trunk:
// if (outerSequence instanceof VirtualNodeSet)
// ((VirtualNodeSet)outerSequence).realize();
Sequence ancestors = outerNodeSet.selectAncestors(contextSet, true, getExpressionId());
if (contextSet.getDocumentSet().intersection(outerNodeSet.getDocumentSet()).getDocumentCount() == 0)
LOG.info("contextSet and outerNodeSet don't share any document");
NewArrayNodeSet temp = new NewArrayNodeSet(100);
for(SequenceIterator i = ancestors.iterate(); i.hasNext(); ) {
NodeProxy p = (NodeProxy)i.nextItem();
ContextItem contextNode = p.getContext();
temp.reset();
while (contextNode != null) {
if (contextNode.getContextId() == getExpressionId())
temp.add(contextNode.getNode());
contextNode = contextNode.getNextDirect();
}
p.clearContext(getExpressionId());
//TODO : understand why we sort here...
temp.sortInDocumentOrder();
for(SequenceIterator j = innerSeq.iterate(); j.hasNext(); ) {
NumericValue v = (NumericValue)j.nextItem();
//Non integers return... nothing, not even an error !
if (!v.hasFractionalPart() && !v.isZero()) {
//... whereas we don't want a sorted array here
//TODO : rename this method as getInDocumentOrder ? -pb
p = temp.get(v.getInt() - 1);
if (p != null) {
//Commented out : but this is probably more complicated (see test case in the same commit)
//p.clearContext(Expression.IGNORE_CONTEXT);
result.add(p);
}
//TODO : does null make sense here ? Well... sometimes ;-)
}
}
}
break;
}
default:
for (SequenceIterator i = outerSequence.iterate(); i.hasNext(); ) {
NodeProxy p = (NodeProxy)i.nextItem();
Sequence temp;
boolean reverseAxis = true;
switch(mode) {
case Constants.ANCESTOR_AXIS:
temp = contextSet.selectAncestors(p, false, Expression.IGNORE_CONTEXT);
break;
case Constants.ANCESTOR_SELF_AXIS:
temp = contextSet.selectAncestors(p, true, Expression.IGNORE_CONTEXT);
break;
case Constants.PARENT_AXIS:
//TODO : understand why the contextSet is not involved here
//NodeProxy.getParent returns a *theoretical* parent
//which is *not* guaranteed to be in the context set !
temp = p.getParents(Expression.NO_CONTEXT_ID);
break;
case Constants.PRECEDING_AXIS:
temp = contextSet.selectPreceding(p, Expression.IGNORE_CONTEXT);
break;
case Constants.PRECEDING_SIBLING_AXIS:
temp = contextSet.selectPrecedingSiblings(p, Expression.IGNORE_CONTEXT);
break;
case Constants.FOLLOWING_SIBLING_AXIS:
temp = contextSet.selectFollowingSiblings(p, Expression.IGNORE_CONTEXT);
reverseAxis = false;
break;
case Constants.FOLLOWING_AXIS:
temp = contextSet.selectFollowing(p, Expression.IGNORE_CONTEXT);
reverseAxis = false;
break;
case Constants.SELF_AXIS:
temp = p;
reverseAxis = false;
break;
default:
//temp = contextSet.selectAncestorDescendant(p, NodeSet.DESCENDANT, false, false);
//break;
throw new IllegalArgumentException("Tested unknown axis");
}
if (!temp.isEmpty()) {
for(SequenceIterator j = innerSeq.iterate(); j.hasNext(); ) {
NumericValue v = (NumericValue)j.nextItem();
//Non integers return... nothing, not even an error !
if (!v.hasFractionalPart() && !v.isZero()) {
int pos = (reverseAxis ? temp.getItemCount() - v.getInt() : v.getInt() - 1);
//Other positions are ignored
if (pos >= 0 && pos < temp.getItemCount()) {
NodeProxy t = (NodeProxy) temp.itemAt(pos);
// for the current context: filter out those context items
// not selected by the positional predicate
ContextItem ctx = t.getContext();
t.clearContext(Expression.IGNORE_CONTEXT);
while (ctx != null) {
if (ctx.getContextId() == outerContextId) {
if (ctx.getNode().getNodeId().equals(p.getNodeId()))
t.addContextNode(outerContextId, ctx.getNode());
} else
t.addContextNode(ctx.getContextId(), ctx.getNode());
ctx = ctx.getNextDirect();
}
result.add(t);
}
}
}
}
}
}
return result;
} else {
boolean reverseAxis = Type.subTypeOf(contextSequence.getItemType(), Type.NODE) &&
(mode == Constants.ANCESTOR_AXIS || mode == Constants.ANCESTOR_SELF_AXIS ||
mode == Constants.PARENT_AXIS || mode == Constants.PRECEDING_AXIS ||
mode == Constants.PRECEDING_SIBLING_AXIS);
Set set = new TreeSet();
ValueSequence result = new ValueSequence();
for(SequenceIterator i = innerSeq.iterate(); i.hasNext();) {
NumericValue v = (NumericValue)i.nextItem();
//Non integers return... nothing, not even an error !
if (!v.hasFractionalPart() && !v.isZero()) {
int pos = (reverseAxis ? contextSequence.getItemCount() - v.getInt() : v.getInt() - 1);
//Other positions are ignored
if (pos >= 0 && pos < contextSequence.getItemCount() && !set.contains(v)) {
result.add(contextSequence.itemAt(pos));
set.add(v);
}
}
}
return result;
}
}
public void setContextDocSet(DocumentSet contextSet) {
super.setContextDocSet(contextSet);
if (getLength() > 0)
getExpression(0).setContextDocSet(contextSet);
}
public int getExecutionMode() {
return executionMode;
}
/* (non-Javadoc)
* @see org.exist.xquery.PathExpr#resetState()
*/
public void resetState(boolean postOptimization) {
super.resetState(postOptimization);
if (!postOptimization)
cached = null;
}
public Expression getParent() {
return parent;
}
public void accept(ExpressionVisitor visitor) {
visitor.visitPredicate(this);
}
public void dump(ExpressionDumper dumper) {
dumper.display("[");
super.dump(dumper);
dumper.display("]");
}
public String toString() {
return "[" + super.toString() + "]";
}
}