The PRUNE MATERALIZED VIEW statement is performed as follows: 1. Perform a range scan of the view table from the view replicas based on the ranges specified in the statement. 2. While reading the paged scan above, for each view row perform a read from all base replicas at the corresponding primary key. If a discrepancy is detected, delete the row in the view table. When reading multiple rows, this is very slow because for each view row we need to performe a single row query on multiple replicas. In this patch we add an option to speed this up by performing many of the single base row reads concurrently, at the concurrency specified in the USING CONCURRENCY clause. Aside from the unit test, I checked manually on a 3-node cluster with 10M rows, using vnodes. There were actually no ghost rows in the test, but we still had to iterate over all view rows and read the corresponding base rows. And actual ghost rows, if there are any, should be a tiny fraction of all rows. I compared concurrencies 1,2,10,100 and the results were: * Pruning with concurrency 1 took total 1416 seconds * Pruning with concurrency 2 took total 731 seconds * Pruning with concurrency 10 took total 234 seconds * Pruning with concurrency 100 took total 171 seconds So after a concurrency of 10 or so we're hitting diminishing returns (at least in this setup). At that point we may be no longer bottlenecked by the reads, but by CPU on the shard that's handling the PRUNE Fixes https://github.com/scylladb/scylladb/issues/27070 Closes scylladb/scylladb#27097 * github.com:scylladb/scylladb: mv: allow setting concurrency in PRUNE MATERIALIZED VIEW cql: add CONCURRENCY to the USING clause
ScyllaDB Documentation
This repository contains the source files for ScyllaDB documentation.
- The
devfolder contains developer-oriented documentation related to the ScyllaDB code base. It is not published and is only available via GitHub. - All other folders and files contain user-oriented documentation related to ScyllaDB and are sources for docs.scylladb.com/manual.
To report a documentation bug or suggest an improvement, open an issue in GitHub issues for this project.
To contribute to the documentation, open a GitHub pull request.
Key Guidelines for Contributors
- The user documentation is written in reStructuredText (RST) - a plaintext markup language similar to Markdown. If you're not familiar with RST, see ScyllaDB RST Examples.
- The developer documentation is written in Markdown. See Basic Markdown Syntax for reference.
- Follow the ScyllaDB Style Guide.
To prevent the build from failing:
-
If you add a new file, ensure it's added to an appropriate toctree, for example:
.. toctree:: :maxdepth: 2 :hidden: Page X </folder1/article1> Page Y </folder1/article2> Your New Page </folder1/your-new-article> -
Make sure the link syntax is correct. See the guidelines on creating links
-
Make sure the section headings are correct. See the guidelines on creating headings Note that the markup must be at least as long as the text in the heading. For example:
---------------------- Prerequisites ----------------------
Building User Documentation
Prerequisites
- Python
- poetry
- make
See the ScyllaDB Sphinx Theme prerequisites to check which versions of the above are currently required.
Mac OS X
You must have a working Homebrew in order to install the needed tools.
You also need the standard utility make.
Check if you have these two items with the following commands:
brew help
make -h
Linux Distributions
Building the user docs should work out of the box on most Linux distributions.
Windows
Use "Bash on Ubuntu on Windows" for the same tools and capabilities as on Linux distributions.
Building the Docs
- Run
make previewto build the documentation. - Preview the built documentation locally at http://127.0.0.1:5500/.
Cleanup
You can clean up all the build products and auto-installed Python stuff with:
make pristine
Information for Contributors
If you are interested in contributing to Scylla docs, please read the Scylla open source page at http://www.scylladb.com/opensource/ and complete a Scylla contributor agreement if needed. We can only accept documentation pull requests if we have a contributor agreement on file for you.
Third-party Documentation
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Do any copying as a separate commit. Always commit an unmodified version first and then do any editing in a separate commit.
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We already have a copy of the Apache license in our tree, so you do not need to commit a copy of the license.
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Include the copyright header from the source file in the edited version. If you are copying an Apache Cassandra document with no copyright header, use:
This document includes material from Apache Cassandra.
Apache Cassandra is Copyright 2009-2014 The Apache Software Foundation.