/*
* Copyright 2004-2013 H2 Group. Multiple-Licensed under the H2 License,
* Version 1.0, and under the Eclipse Public License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.lealone.command.dml;
import java.util.Map;
import java.util.TreeMap;
import java.util.Map.Entry;
import org.lealone.command.CommandInterface;
import org.lealone.command.Prepared;
import org.lealone.dbobject.table.Column;
import org.lealone.engine.Database;
import org.lealone.engine.Session;
import org.lealone.expression.Expression;
import org.lealone.expression.ExpressionColumn;
import org.lealone.result.LocalResult;
import org.lealone.result.ResultInterface;
import org.lealone.value.Value;
import org.lealone.value.ValueString;
/**
* This class represents the statement
* EXPLAIN
*/
public class Explain extends Prepared {
private Prepared command;
private LocalResult result;
private boolean executeCommand;
public Explain(Session session) {
super(session);
}
public void setCommand(Prepared command) {
this.command = command;
}
public void prepare() {
command.prepare();
}
public void setExecuteCommand(boolean executeCommand) {
this.executeCommand = executeCommand;
}
public ResultInterface queryMeta() {
return query(-1);
}
public ResultInterface query(int maxrows) {
Column column = new Column("PLAN", Value.STRING);
Database db = session.getDatabase();
ExpressionColumn expr = new ExpressionColumn(db, column);
Expression[] expressions = { expr };
result = new LocalResult(session, expressions, 1);
if (maxrows >= 0) {
String plan;
if (executeCommand) {
db.statisticsStart();
if (command.isQuery()) {
command.query(maxrows);
} else {
command.update();
}
plan = command.getPlanSQL();
Map<String, Integer> statistics = db.statisticsEnd();
if (statistics != null) {
int total = 0;
for (Entry<String, Integer> e : statistics.entrySet()) {
total += e.getValue();
}
if (total > 0) {
statistics = new TreeMap<String, Integer>(statistics);
StringBuilder buff = new StringBuilder();
buff.append("total: ").append(total).append('\n');
for (Entry<String, Integer> e : statistics.entrySet()) {
int value = e.getValue();
int percent = (int) (100L * value / total);
buff.append(e.getKey()).append(": ").append(value).append(" (").append(percent).append("%)\n");
}
plan += "\n/*\n" + buff.toString() + "*/";
}
}
} else {
plan = command.getPlanSQL();
}
add(plan);
}
result.done();
return result;
}
private void add(String text) {
Value[] row = { ValueString.get(text) };
result.addRow(row);
}
public boolean isQuery() {
return true;
}
public boolean isTransactional() {
return true;
}
public boolean isReadOnly() {
return command.isReadOnly();
}
public int getType() {
return CommandInterface.EXPLAIN;
}
}