org.h2.result.MergedResult 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.result;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import org.h2.util.Utils;
import org.h2.value.Value;
/**
* Merged result. Used to combine several results into one. Merged result will
* contain rows from all appended results. Results are not required to have the
* same lists of columns, but required to have compatible column definitions,
* for example, if one result has a {@link java.sql.Types#VARCHAR} column
* {@code NAME} then another results that have {@code NAME} column should also
* define it with the same type.
*/
public final class MergedResult {
private final ArrayList> data = Utils.newSmallArrayList();
private final ArrayList columns = Utils.newSmallArrayList();
/**
* Appends a result.
*
* @param result
* result to append
*/
public void add(ResultInterface result) {
int count = result.getVisibleColumnCount();
if (count == 0) {
return;
}
SimpleResult.Column[] cols = new SimpleResult.Column[count];
for (int i = 0; i < count; i++) {
SimpleResult.Column c = new SimpleResult.Column(result.getAlias(i), result.getColumnName(i),
result.getColumnType(i));
cols[i] = c;
if (!columns.contains(c)) {
columns.add(c);
}
}
while (result.next()) {
if (count == 1) {
data.add(Collections.singletonMap(cols[0], result.currentRow()[0]));
} else {
HashMap map = new HashMap<>();
for (int i = 0; i < count; i++) {
SimpleResult.Column ci = cols[i];
map.put(ci, result.currentRow()[i]);
}
data.add(map);
}
}
}
/**
* Returns merged results.
*
* @return result with rows from all appended result sets
*/
public SimpleResult getResult() {
SimpleResult result = new SimpleResult();
for (SimpleResult.Column c : columns) {
result.addColumn(c);
}
for (Map map : data) {
Value[] row = new Value[columns.size()];
for (Map.Entry entry : map.entrySet()) {
row[columns.indexOf(entry.getKey())] = entry.getValue();
}
result.addRow(row);
}
return result;
}
@Override
public String toString() {
return columns + ": " + data.size();
}
}