?? valueexpression.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.engine.Session;
import org.h2.index.IndexCondition;
import org.h2.message.Message;
import org.h2.table.ColumnResolver;
import org.h2.table.TableFilter;
import org.h2.value.Value;
import org.h2.value.ValueBoolean;
import org.h2.value.ValueNull;
/**
* An expression representing a constant value.
*/
public class ValueExpression extends Expression {
private Value value;
public static final ValueExpression NULL = new ValueExpression(ValueNull.INSTANCE);
public static final ValueExpression DEFAULT = new ValueExpression(ValueNull.INSTANCE);
public static ValueExpression get(Value v) {
if (v == ValueNull.INSTANCE) {
return ValueExpression.NULL;
}
return new ValueExpression(v);
}
private ValueExpression(Value value) {
this.value = value;
}
public Value getValue(Session session) {
return value;
}
public int getType() {
return value.getType();
}
public void createIndexConditions(Session session, TableFilter filter) {
if (value.getType() == Value.BOOLEAN) {
boolean v = ((ValueBoolean) value).getBoolean().booleanValue();
if (!v) {
filter.addIndexCondition(new IndexCondition(Comparison.FALSE, null, this));
}
}
}
public Expression getNotIfPossible(Session session) {
return new Comparison(session, Comparison.EQUAL, this, ValueExpression.get(ValueBoolean.get(false)));
}
public void mapColumns(ColumnResolver resolver, int level) throws SQLException {
}
public Expression optimize(Session session) throws SQLException {
return this;
}
public boolean isConstant() {
return true;
}
public boolean isValueSet() {
return true;
}
public void setEvaluatable(TableFilter tableFilter, boolean b) {
}
public int getScale() {
return value.getScale();
}
public long getPrecision() {
return value.getPrecision();
}
public int getDisplaySize() {
return value.getDisplaySize();
}
public String getSQL() {
if (this == DEFAULT) {
return "DEFAULT";
} else {
return value.getSQL();
}
}
public void updateAggregate(Session session) throws SQLException {
}
public boolean isEverything(ExpressionVisitor visitor) {
switch (visitor.type) {
case ExpressionVisitor.OPTIMIZABLE_MIN_MAX_COUNT_ALL:
return true;
case ExpressionVisitor.DETERMINISTIC:
case ExpressionVisitor.READONLY:
return true;
case ExpressionVisitor.INDEPENDENT:
return true;
case ExpressionVisitor.EVALUATABLE:
return true;
case ExpressionVisitor.SET_MAX_DATA_MODIFICATION_ID:
return true;
case ExpressionVisitor.NOT_FROM_RESOLVER:
return true;
case ExpressionVisitor.GET_DEPENDENCIES:
return true;
default:
throw Message.getInternalError("type=" + visitor.type);
}
}
public int getCost() {
return 0;
}
}
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