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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-6153) Revised operator framework
Date Wed, 14 Feb 2018 23:01:00 GMT

    [ https://issues.apache.org/jira/browse/DRILL-6153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16364901#comment-16364901
] 

ASF GitHub Bot commented on DRILL-6153:
---------------------------------------

Github user ppadma commented on a diff in the pull request:

    https://github.com/apache/drill/pull/1121#discussion_r168325261
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/protocol/OperatorExec.java
---
    @@ -0,0 +1,127 @@
    +/*
    + * 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.drill.exec.physical.impl.protocol;
    +
    +import org.apache.drill.exec.ops.OperatorContext;
    +
    +/**
    + * Core protocol for a Drill operator execution.
    + *
    + * <h4>Lifecycle</h4>
    + *
    + * <ul>
    + * <li>Creation via an operator-specific constructor in the
    + * corresponding <tt>RecordBatchCreator</tt>.</li>
    + * <li><tt>bind()</tt> called to provide the operator services.</li>
    + * <li><tt>buildSchema()</tt> called to define the schema before
    + * fetching the first record batch.</li>
    + * <li><tt>next()</tt> called repeatedly to prepare each new record
    + * batch until EOF or until cancellation.</li>
    + * <li><tt>cancel()</tt> called if the operator should quit early.</li>
    + * <li><tt>close()</tt> called to release resources. Note that
    + * <tt>close()</tt> is called in response to:<ul>
    + *   <li>EOF</li>
    + *   <li>After <tt>cancel()</tt></li>
    + *   <li>After an exception is thrown.</li></ul></li>
    + * </ul>
    + *
    + * <h4>Error Handling</h4>
    + *
    + * Any method can throw an (unchecked) exception. (Drill does not use
    + * checked exceptions.) Preferably, the code will throw a
    + * <tt>UserException</tt> that explains the error to the user. If any
    + * other kind of exception is thrown, then the enclosing class wraps it
    + * in a generic <tt>UserException</tt> that indicates that "something went
    + * wrong", which is less than ideal.
    + *
    + * <h4>Result Set</h4>
    + * The operator "publishes" a result set in response to returning
    + * <tt>true</tt> from <tt>next()</tt> by populating a
    + * {@link BatchAccesor} provided via {@link #batchAccessor()}. For
    + * compatibility with other Drill operators, the set of vectors within
    + * the batch must be the same from one batch to the next.
    + */
    +
    +public interface OperatorExec {
    +
    +  /**
    +   * Bind this operator to the context. The context provides access
    +   * to per-operator, per-fragment and per-Drillbit services.
    +   * Also provides access to the operator definition (AKA "pop
    +   * config") for this operator.
    +   *
    +   * @param context operator context
    +   */
    +
    +  public void bind(OperatorContext context);
    +
    +  /**
    +   * Provides a generic access mechanism to the batch's output data.
    +   * This method is called after a successful return from
    +   * {@link #buildSchema()} and {@link #next()}. The batch itself
    +   * can be held in a standard {@link VectorContainer}, or in some
    +   * other structure more convenient for this operator.
    +   *
    +   * @return the access for the batch's output container
    +   */
    +
    +  BatchAccessor batchAccessor();
    +
    +  /**
    +   * Retrieves the schema of the batch before the first actual batch
    +   * of data. The schema is returned via an empty batch (no rows,
    +   * only schema) from {@link #batchAccessor()}.
    +   *
    +   * @return true if a schema is available, false if the operator
    +   * reached EOF before a schema was found
    +   */
    +
    +  boolean buildSchema();
    +
    +  /**
    +   * Retrieves the next batch of data. The data is returned via
    +   * the {@link #batchAccessor()} method.
    +   *
    +   * @return true if another batch of data is available, false if
    +   * EOF was reached and no more data is available
    +   */
    +
    +  boolean next();
    +
    +  /**
    +   * Alerts the operator that the query was cancelled. Generally
    +   * optional, but allows the operator to realize that a cancellation
    --- End diff --
    
    why is this optional ?


> Revised operator framework
> --------------------------
>
>                 Key: DRILL-6153
>                 URL: https://issues.apache.org/jira/browse/DRILL-6153
>             Project: Apache Drill
>          Issue Type: Improvement
>            Reporter: Paul Rogers
>            Assignee: Paul Rogers
>            Priority: Major
>             Fix For: 1.13.0
>
>
> Adds the core operator framework which is the foundation for the revised scan operators.
This is another incremental part of the batch sizing project.



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