org.h2.mvstore.db.MVPlainTempResult Maven / Gradle / Ivy
/*
* Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.mvstore.db;
import org.h2.engine.Database;
import org.h2.expression.Expression;
import org.h2.message.DbException;
import org.h2.mvstore.Cursor;
import org.h2.mvstore.MVMap;
import org.h2.mvstore.MVMap.Builder;
import org.h2.result.ResultExternal;
import org.h2.value.Value;
import org.h2.value.ValueRow;
/**
* Plain temporary result.
*/
class MVPlainTempResult extends MVTempResult {
/**
* Map with identities of rows as keys rows as values.
*/
private final MVMap map;
/**
* Counter for the identities of rows. A separate counter is used instead of
* {@link #rowCount} because rows due to presence of {@link #removeRow(Value[])}
* method to ensure that each row will have an own identity.
*/
private long counter;
/**
* Cursor for the {@link #next()} method.
*/
private Cursor cursor;
/**
* Creates a shallow copy of the result.
*
* @param parent
* parent result
*/
private MVPlainTempResult(MVPlainTempResult parent) {
super(parent);
this.map = parent.map;
}
/**
* Creates a new plain temporary result. This result does not sort its rows,
* but it can be used in index-sorted queries and it can preserve additional
* columns for WITH TIES processing.
*
* @param database
* database
* @param expressions
* column expressions
* @param visibleColumnCount
* count of visible columns
* @param resultColumnCount
* the number of columns including visible columns and additional
* virtual columns for ORDER BY clause
*/
MVPlainTempResult(Database database, Expression[] expressions, int visibleColumnCount, int resultColumnCount) {
super(database, expressions, visibleColumnCount, resultColumnCount);
ValueDataType valueType = new ValueDataType(database, new int[resultColumnCount]);
Builder builder = new MVMap.Builder()
.valueType(valueType).singleWriter();
map = store.openMap("tmp", builder);
}
@Override
public int addRow(Value[] values) {
assert parent == null;
map.append(counter++, ValueRow.get(values));
return ++rowCount;
}
@Override
public boolean contains(Value[] values) {
throw DbException.getUnsupportedException("contains()");
}
@Override
public synchronized ResultExternal createShallowCopy() {
if (parent != null) {
return parent.createShallowCopy();
}
if (closed) {
return null;
}
childCount++;
return new MVPlainTempResult(this);
}
@Override
public Value[] next() {
if (cursor == null) {
cursor = map.cursor(null);
}
if (!cursor.hasNext()) {
return null;
}
cursor.next();
Value[] currentRow = cursor.getValue().getList();
if (hasEnum) {
fixEnum(currentRow);
}
return currentRow;
}
@Override
public int removeRow(Value[] values) {
throw DbException.getUnsupportedException("removeRow()");
}
@Override
public void reset() {
cursor = null;
}
}