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 * this list of conditions and the following disclaimer in the documentation
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 * contributors may be used to endorse or promote products derived from this
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package org.hsqldb_voltpatches;

/**
 * Implementation of ORDER BY operations
 *
 * @author Fred Toussi (fredt@users dot sourceforge.net)
 * @version 1.9.0
 * @since 1.9.0
 */
public class ExpressionOrderBy extends Expression {

    private boolean isDescending;
    private boolean isNullsLast;

    ExpressionOrderBy(Expression e) {

        super(OpTypes.ORDER_BY);

        nodes       = new Expression[UNARY];
        nodes[LEFT] = e;
    }

    /**
     * Set an ORDER BY column expression DESC
     */
    void setDescending() {
        isDescending = true;
    }

    /**
     * Is an ORDER BY column expression DESC
     */
    boolean isDescending() {
        return isDescending;
    }

    /**
     * Set an ORDER BY column NULL ordering
     */
    void setNullsLast() {
        isNullsLast = true;
    }

    /**
     * Is an ORDER BY column NULL ordering
     */
    boolean isNullsLast() {
        return isNullsLast;
    }

    public Object getValue(Session session) {
        return nodes[LEFT].getValue(session);
    }

    public void resolveTypes(Session session, Expression parent) {

        nodes[LEFT].resolveTypes(session, parent);

        if (nodes[LEFT].isParam) {
            throw Error.error(ErrorCode.X_42567);
        }

        dataType = nodes[LEFT].dataType;
    }

    public String getSQL() {

        StringBuffer sb = new StringBuffer();

        sb.append(Tokens.T_ORDER).append(' ').append(Tokens.T_BY).append(' ');

        if (nodes[LEFT].alias != null) {
            sb.append(nodes[LEFT].alias.name);
        } else {
            sb.append(nodes[LEFT].getSQL());
        }

        if (isDescending) {
            sb.append(' ').append(Tokens.T_DESC);
        }

        return sb.toString();
    }

    protected String describe(Session session, int blanks) {

        StringBuffer sb = new StringBuffer();

        sb.append('\n');

        for (int i = 0; i < blanks; i++) {
            sb.append(' ');
        }

        sb.append(Tokens.T_ORDER).append(' ').append(Tokens.T_BY);
        sb.append(' ');

        if (isDescending) {
            sb.append(Tokens.T_DESC).append(' ');
        }

        return sb.toString();
    }
}