studio.raptor.sqlparser.fast.expression.ValueExpression Maven / Gradle / Ivy

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/*
 * Copyright 2004-2014 H2 Group. Multiple-Licensed under the MPL 2.0,
 * and the EPL 1.0 (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package studio.raptor.sqlparser.fast.expression;

import studio.raptor.sqlparser.fast.message.ParseException;
import studio.raptor.sqlparser.fast.table.ColumnResolver;
import studio.raptor.sqlparser.fast.value.Value;
import studio.raptor.sqlparser.fast.value.ValueNull;

/**
 * An expression representing a constant value.
 */
public class ValueExpression extends Expression {

  /**
   * The expression represents ValueNull.INSTANCE.
   */
  private static final Object NULL = new ValueExpression(ValueNull.INSTANCE);

  /**
   * This special expression represents the default value. It is used for
   * UPDATE statements of the form SET COLUMN = DEFAULT. The value is
   * ValueNull.INSTANCE, but should never be accessed.
   */
  private static final Object DEFAULT = new ValueExpression(ValueNull.INSTANCE);

  private final Value value;

  private ValueExpression(Value value) {
    this.value = value;
  }

  /**
   * Get the NULL expression.
   *
   * @return the NULL expression
   */
  public static ValueExpression getNull() {
    return (ValueExpression) NULL;
  }

  /**
   * Get the DEFAULT expression.
   *
   * @return the DEFAULT expression
   */
  public static ValueExpression getDefault() {
    return (ValueExpression) DEFAULT;
  }

  /**
   * Create a new expression with the given value.
   *
   * @param value the value
   * @return the expression
   */
  public static ValueExpression get(Value value) {
    if (value == ValueNull.INSTANCE) {
      return getNull();
    }
    return new ValueExpression(value);
  }

  @Override
  public Value getValue() {
    return value;
  }

  @Override
  public int getType() {
    return value.getType();
  }

  @Override
  public void mapColumns(ColumnResolver resolver, int level) {
    // nothing to do
  }

  @Override
  public Expression optimize() {
    return this;
  }

  @Override
  public boolean isConstant() {
    return true;
  }

  @Override
  public boolean isValueSet() {
    return true;
  }

  @Override
  public String getSQL() {
    if (this == DEFAULT) {
      return "DEFAULT";
    }
    return value.getSQL();
  }

  @Override
  public boolean isEverything(ExpressionVisitor visitor) {
    switch (visitor.getType()) {
      case ExpressionVisitor.OPTIMIZABLE_MIN_MAX_COUNT_ALL:
      case ExpressionVisitor.DETERMINISTIC:
      case ExpressionVisitor.READONLY:
      case ExpressionVisitor.INDEPENDENT:
      case ExpressionVisitor.EVALUATABLE:
      case ExpressionVisitor.SET_MAX_DATA_MODIFICATION_ID:
      case ExpressionVisitor.NOT_FROM_RESOLVER:
      case ExpressionVisitor.GET_DEPENDENCIES:
      case ExpressionVisitor.QUERY_COMPARABLE:
      case ExpressionVisitor.GET_COLUMNS:
        return true;
      default:
        throw ParseException.throwInternalError("type=" + visitor.getType());
    }
  }

}