?? variable.java
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/*
* Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.expression;
import java.sql.SQLException;
import org.h2.command.Parser;
import org.h2.engine.Session;
import org.h2.message.Message;
import org.h2.table.ColumnResolver;
import org.h2.table.TableFilter;
import org.h2.value.Value;
/**
* A user defined variable, for example: @ID.
*/
public class Variable extends Expression {
private final String name;
private Value lastValue;
public Variable(Session session, String name) {
this.name = name;
lastValue = session.getVariable(name);
}
public int getCost() {
return 0;
}
public int getDisplaySize() {
return lastValue.getDisplaySize();
}
public long getPrecision() {
return lastValue.getPrecision();
}
public String getSQL() {
return "@" + Parser.quoteIdentifier(name);
}
public int getScale() {
return lastValue.getScale();
}
public int getType() {
return lastValue.getType();
}
public Value getValue(Session session) throws SQLException {
lastValue = session.getVariable(name);
return lastValue;
}
public boolean isEverything(ExpressionVisitor visitor) {
switch(visitor.type) {
case ExpressionVisitor.OPTIMIZABLE_MIN_MAX_COUNT_ALL:
return true;
case ExpressionVisitor.DETERMINISTIC:
return false;
case ExpressionVisitor.READONLY:
return true;
case ExpressionVisitor.INDEPENDENT:
return true;
case ExpressionVisitor.EVALUATABLE:
// the value will be evaluated at execute time
return true;
case ExpressionVisitor.SET_MAX_DATA_MODIFICATION_ID:
// it is checked independently if the value is the same as the last time
return true;
case ExpressionVisitor.NOT_FROM_RESOLVER:
return true;
case ExpressionVisitor.GET_DEPENDENCIES:
return true;
default:
throw Message.getInternalError("type="+visitor.type);
}
}
public void mapColumns(ColumnResolver resolver, int level) throws SQLException {
}
public Expression optimize(Session session) throws SQLException {
return this;
}
public void setEvaluatable(TableFilter tableFilter, boolean value) {
}
public void updateAggregate(Session session) throws SQLException {
}
public String getName() {
return name;
}
}
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