/*
* Copyright 2004-2023 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.expression;
import org.h2.command.Prepared;
import org.h2.engine.SessionLocal;
import org.h2.message.DbException;
import org.h2.value.TypeInfo;
import org.h2.value.Value;
import org.h2.value.ValueBigint;
/**
* Represents the ROWNUM function.
*/
public final class Rownum extends Operation0 {
private final Prepared prepared;
private boolean singleRow;
public Rownum(Prepared prepared) {
if (prepared == null) {
throw DbException.getInternalError();
}
this.prepared = prepared;
}
@Override
public Value getValue(SessionLocal session) {
return ValueBigint.get(prepared.getCurrentRowNumber());
}
@Override
public TypeInfo getType() {
return TypeInfo.TYPE_BIGINT;
}
@Override
public StringBuilder getUnenclosedSQL(StringBuilder builder, int sqlFlags) {
return builder.append("ROWNUM()");
}
@Override
public Expression optimize(SessionLocal session) {
return singleRow ? ValueExpression.get(ValueBigint.get(1L)) : this;
}
@Override
public boolean isEverything(ExpressionVisitor visitor) {
switch (visitor.getType()) {
case ExpressionVisitor.QUERY_COMPARABLE:
case ExpressionVisitor.OPTIMIZABLE_AGGREGATE:
case ExpressionVisitor.DETERMINISTIC:
case ExpressionVisitor.INDEPENDENT:
case ExpressionVisitor.EVALUATABLE:
return false;
case ExpressionVisitor.DECREMENT_QUERY_LEVEL:
if (visitor.getQueryLevel() > 0) {
singleRow = true;
}
//$FALL-THROUGH$
default:
return true;
}
}
@Override
public int getCost() {
return 0;
}
}