| /* |
| * 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.phoenix.expression; |
| |
| import java.util.List; |
| |
| import org.apache.hadoop.hbase.io.ImmutableBytesWritable; |
| import org.apache.hadoop.io.Writable; |
| import org.apache.phoenix.expression.visitor.ExpressionVisitor; |
| import org.apache.phoenix.schema.PDatum; |
| import org.apache.phoenix.schema.tuple.Tuple; |
| |
| |
| /** |
| * |
| * Interface for general expression evaluation |
| * |
| * |
| * @since 0.1 |
| */ |
| public interface Expression extends PDatum, Writable { |
| |
| /** |
| * Access the value by setting a pointer to it (as opposed to making |
| * a copy of it which can be expensive) |
| * @param tuple Single row result during scan iteration |
| * @param ptr Pointer to byte value being accessed |
| * @return true if the expression could be evaluated (i.e. ptr was set) |
| * and false otherwise |
| */ |
| boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr); |
| |
| /** |
| * Means of traversing expression tree through visitor. |
| * @param visitor |
| */ |
| <T> T accept(ExpressionVisitor<T> visitor); |
| |
| /** |
| * @return the child expressions |
| */ |
| List<Expression> getChildren(); |
| |
| /** |
| * Resets the state of a expression back to its initial state and |
| * enables the expession to be evaluated incrementally (which |
| * occurs during filter evaluation where we see one key value at |
| * a time; it's possible to evaluate immediately rather than |
| * wait until all key values have been seen). Note that when |
| * evaluating incrementally, you must call this method before |
| * processing a new row. |
| */ |
| void reset(); |
| |
| /** |
| * @return true if the expression can be evaluated on the client |
| * side with out server state. If a sequence is involved, you |
| * still need a Tuple from a {@link org.apache.phoenix.iterate.SequenceResultIterator}, |
| * but otherwise the Tuple may be null. |
| */ |
| boolean isStateless(); |
| |
| /** |
| * @return Determinism enum |
| */ |
| Determinism getDeterminism(); |
| |
| /** |
| * Determines if an evaluate is required after partial evaluation |
| * is run. For example, in the case of an IS NULL expression, we |
| * only know we can return TRUE after all KeyValues have been seen |
| * while an expression is used in the context of a filter. |
| * @return |
| */ |
| boolean requiresFinalEvaluation(); |
| |
| /** |
| * Determines if expression needs to be cloned in {@link org.apache.phoenix.compile.RowProjector} |
| * @return |
| */ |
| boolean isCloneExpression(); |
| } |