liyafan82 opened a new pull request #8788: [FLINK-12886][Table SQL / Runtime] Support container memory segment URL: https://github.com/apache/flink/pull/8788 <!-- *Thank you very much for contributing to Apache Flink - we are happy that you want to help us improve Flink. To help the community review your contribution in the best possible way, please go through the checklist below, which will get the contribution into a shape in which it can be best reviewed.* *Please understand that we do not do this to make contributions to Flink a hassle. In order to uphold a high standard of quality for code contributions, while at the same time managing a large number of contributions, we need contributors to prepare the contributions well, and give reviewers enough contextual information for the review. Please also understand that contributions that do not follow this guide will take longer to review and thus typically be picked up with lower priority by the community.* ## Contribution Checklist - Make sure that the pull request corresponds to a [JIRA issue](https://issues.apache.org/jira/projects/FLINK/issues). Exceptions are made for typos in JavaDoc or documentation files, which need no JIRA issue. - Name the pull request in the form "[FLINK-XXXX] [component] Title of the pull request", where *FLINK-XXXX* should be replaced by the actual issue number. Skip *component* if you are unsure about which is the best component. Typo fixes that have no associated JIRA issue should be named following this pattern: `[hotfix] [docs] Fix typo in event time introduction` or `[hotfix] [javadocs] Expand JavaDoc for PuncuatedWatermarkGenerator`. - Fill out the template below to describe the changes contributed by the pull request. That will give reviewers the context they need to do the review. - Make sure that the change passes the automated tests, i.e., `mvn clean verify` passes. You can set up Travis CI to do that following [this guide](http://flink.apache.org/contribute-code.html#best-practices). - Each pull request should address only one issue, not mix up code from multiple issues. - Each commit in the pull request has a meaningful commit message (including the JIRA id) - Once all items of the checklist are addressed, remove the above text and this checklist, leaving only the filled out template below. **(The sections below can be removed for hotfixes of typos)** --> ## What is the purpose of the change We observe that in many scenarios, the operations/algorithms are based on an array of MemorySegment. These memory segments form a large, combined, and continuous memory space. For example, suppose we have an array of n memory segments. Memory addresses from 0 to segment_size - 1 are served by the first memory segment; memory addresses from segment_size to 2 * segment_size - 1 are served by the second memory segment, and so on. Specific algorithms decide the actual MemorySegment to serve the operation requests. For some rare cases, two or more memory segments serve the requests. There are many operations based on such a paradigm, for example, BinaryString#matchAt, SegmentsUtil#copyToBytes, LongHashPartition#MatchIterator#get, etc. The problem is that, for memory segment array based operations, large amounts of code is devoted to 1. Computing the memory segment index & offset within the memory segment. 2. Processing boundary cases. For example, to write an integer, there are only 2 bytes left in the first memory segment, and the remaining 2 bytes must be written to the next memory segment. 3. Differentiate processing for short/long data. For example, when copying memory data to a byte array. Different methods are implemented for cases when 1) the data fits in a single segment; 2) the data spans multiple segments. Therefore, there are much duplicated code to achieve above purposes. What is worse, this paradigm significantly increases the amount of code, making the code more difficult to read and maintain. Furthermore, it easily gives rise to bugs which difficult to find and debug. To address these problems, we propose a new type of memory segment: ContainerMemorySegment. It is based on an array of underlying memory segments with the same size. It extends from the MemorySegment base class, so it provides all the functionalities provided by MemorySegment. In addition, it hides all the details for dealing with specific memory segments, and acts as if it were a big continuous memory region. With this new type of memory segment, many operations/algorithms can be greatly simplified, without affecting performance. This is because, 1. Many checks, boundary processing are already there. We just move them to the new class. 2. We optimize the implementation of the new class, so the special optimizations (e.g. optimizations for short data) are still preserved. ## Brief change log *(for example:)* - implement the new memory segment (ContainerMemorySegment) - provide unit tests in ContainerMemorySegmentTest ## Verifying this change This change added tests and can be verified by ContainerMemorySegmentTest: ## Does this pull request potentially affect one of the following parts: - Dependencies (does it add or upgrade a dependency): (yes) - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: (no) - The serializers: (no) - The runtime per-record code paths (performance sensitive): (yes) - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (no) - The S3 file system connector: (no) ## Documentation - Does this pull request introduce a new feature? (yes) - If yes, how is the feature documented? (JavaDocs)
---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
