io.questdb.griffin.engine.table.HeapRowCursor Maven / Gradle / Ivy
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* Copyright (c) 2014-2019 Appsicle
* Copyright (c) 2019-2020 QuestDB
*
* Licensed 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,
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package io.questdb.griffin.engine.table;
import io.questdb.cairo.sql.RowCursor;
import io.questdb.std.IntLongPriorityQueue;
import io.questdb.std.ObjList;
class HeapRowCursor implements RowCursor {
private final IntLongPriorityQueue heap;
private ObjList cursors;
public HeapRowCursor() {
this.heap = new IntLongPriorityQueue();
}
@Override
public boolean hasNext() {
return heap.hasNext();
}
@Override
public long next() {
int idx = heap.popIndex();
RowCursor cursor = cursors.getQuick(idx);
return cursor.hasNext() ? heap.popAndReplace(idx, cursor.next()) : heap.popValue();
}
public void of(ObjList cursors) {
int nCursors = cursors.size();
this.cursors = cursors;
this.heap.clear();
for (int i = 0; i < nCursors; i++) {
final RowCursor cursor = cursors.getQuick(i);
if (cursor.hasNext()) {
heap.add(i, cursor.next());
}
}
}
}