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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.expr.flwor;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.expr.sort.GenericAtomicComparer;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.transpile.CSharpSuppressWarnings;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
/**
* Represents the tuple stream delivered by an "group by" clause. This groups the tuple stream supplied
* as its input, and outputs a new set of tuples one per group of the input tuples. No groups are output
* until all the groups have been read.
*/
public class GroupByClausePull extends TuplePull {
private final TuplePull base;
private final GroupByClause groupByClause;
/*@Nullable*/ Iterator> groupIterator;
private final GenericAtomicComparer[] comparers;
public GroupByClausePull(TuplePull base, GroupByClause groupBy, XPathContext context) {
this.base = base;
this.groupByClause = groupBy;
comparers = new GenericAtomicComparer[groupBy.comparers.length];
for (int i = 0; i < comparers.length; i++) {
comparers[i] = groupBy.comparers[i].provideContext(context);
}
}
/**
* Move on to the next tuple. Before returning, this method must set all the variables corresponding
* to the "returned" tuple in the local stack frame associated with the context object
*
* @param context the dynamic evaluation context
* @return true if another tuple has been generated; false if the tuple stream is exhausted. If the
* method returns false, the values of the local variables corresponding to this tuple stream
* are undefined.
*/
@Override
@CSharpSuppressWarnings("UnsafeIteratorConversion")
public boolean nextTuple(XPathContext context) throws XPathException {
if (groupIterator == null) {
// First do the grouping
TupleExpression groupingTupleExpr = groupByClause.getGroupingTupleExpression();
TupleExpression retainedTupleExpr = groupByClause.getRetainedTupleExpression();
HashMap> map = new HashMap<>();
while (base.nextTuple(context)) {
GroupByClause.ObjectToBeGrouped otbg = new GroupByClause.ObjectToBeGrouped();
Sequence[] groupingValues = groupingTupleExpr.evaluateItem(context).getMembers();
GroupByClausePush.checkGroupingValues(groupingValues);
otbg.groupingValues = new Tuple(groupingValues);
otbg.retainedValues = retainedTupleExpr.evaluateItem(context);
Object key = groupByClause.getComparisonKey(otbg.groupingValues, comparers);
List group = map.get(key);
GroupByClausePush.addToGroup(key, otbg, group, map);
}
// get an iterator over the groups
groupIterator = map.values().iterator();
}
if (groupIterator.hasNext()) {
List group = groupIterator.next();
groupByClause.processGroup(group, context);
return true;
} else {
return false;
}
}
/**
* Close the tuple stream, indicating that although not all tuples have been read,
* no further tuples are required and resources can be released
*/
@Override
public void close() {
base.close();
groupIterator = null;
}
}
// Copyright (c) 2011-2022 Saxonica Limited