| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to you under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.calcite.rex; |
| |
| import org.apache.calcite.rel.type.RelDataType; |
| import org.apache.calcite.rel.type.RelDataTypeField; |
| import org.apache.calcite.sql.SqlKind; |
| |
| import org.checkerframework.checker.nullness.qual.Nullable; |
| |
| import static com.google.common.base.Preconditions.checkArgument; |
| |
| /** |
| * Access to a field of a row-expression. |
| * |
| * <p>You might expect to use a <code>RexFieldAccess</code> to access columns of |
| * relational tables, for example, the expression <code>emp.empno</code> in the |
| * query |
| * |
| * <blockquote> |
| * <pre>SELECT emp.empno FROM emp</pre> |
| * </blockquote> |
| * |
| * <p>but there is a specialized expression {@link RexInputRef} for this |
| * purpose. So in practice, <code>RexFieldAccess</code> is usually used to |
| * access fields of correlating variables, for example the expression |
| * <code>emp.deptno</code> in |
| * |
| * <blockquote> |
| * <pre>SELECT ename |
| * FROM dept |
| * WHERE EXISTS ( |
| * SELECT NULL |
| * FROM emp |
| * WHERE emp.deptno = dept.deptno |
| * AND gender = 'F')</pre> |
| * </blockquote> |
| */ |
| public class RexFieldAccess extends RexNode { |
| //~ Instance fields -------------------------------------------------------- |
| |
| private final RexNode expr; |
| private final RelDataTypeField field; |
| |
| //~ Constructors ----------------------------------------------------------- |
| |
| RexFieldAccess( |
| RexNode expr, |
| RelDataTypeField field) { |
| checkValid(expr, field); |
| this.expr = expr; |
| this.field = field; |
| this.digest = expr + "." + field.getName(); |
| } |
| |
| //~ Methods ---------------------------------------------------------------- |
| |
| private static void checkValid(RexNode expr, RelDataTypeField field) { |
| RelDataType exprType = expr.getType(); |
| int fieldIdx = field.getIndex(); |
| checkArgument(fieldIdx >= 0 && fieldIdx < exprType.getFieldList().size() |
| && exprType.getFieldList().get(fieldIdx).equals(field), |
| "Field %s does not exist for expression %s", field, expr); |
| } |
| |
| public RelDataTypeField getField() { |
| return field; |
| } |
| |
| @Override public RelDataType getType() { |
| return field.getType(); |
| } |
| |
| @Override public SqlKind getKind() { |
| return SqlKind.FIELD_ACCESS; |
| } |
| |
| @Override public <R> R accept(RexVisitor<R> visitor) { |
| return visitor.visitFieldAccess(this); |
| } |
| |
| @Override public <R, P> R accept(RexBiVisitor<R, P> visitor, P arg) { |
| return visitor.visitFieldAccess(this, arg); |
| } |
| |
| /** |
| * Returns the expression whose field is being accessed. |
| */ |
| public RexNode getReferenceExpr() { |
| return expr; |
| } |
| |
| @Override public boolean equals(@Nullable Object o) { |
| if (this == o) { |
| return true; |
| } |
| if (o == null || getClass() != o.getClass()) { |
| return false; |
| } |
| |
| RexFieldAccess that = (RexFieldAccess) o; |
| |
| return field.equals(that.field) && expr.equals(that.expr); |
| } |
| |
| @Override public int hashCode() { |
| int result = expr.hashCode(); |
| result = 31 * result + field.hashCode(); |
| return result; |
| } |
| } |