9fd312d157
https://github.com/scylladb/scylladb/issues/24962 introduced memtable overlap checks to cache tombstone GC. This was observed to be very strict and greatly reduce the effectiveness of tombstone GC in the cache, especially for MV workloads, which regularly recycle old timestamp into new writes, so the memtable often has smaller min live timestamp than the timestamp of the tombstones in the cache. When creating a new memtable, save a snapshot of the tombstone gc state. This snapshot is used later to exclude this memtable from overlap checks for tombstones, whose token have an expiry time larger than that of the tombstone, meaning: all writes in this memtable were produced at a point in time when the current tombstone has already expired. This has the following implications: * The partition the tombstone is part of was already repaired at the time the memtable was created. * All writes in the memtable were produced *after* this tombstone's expiry time, these writes cannot be possibly relevant for this tombstone. Based on this, such memtables are excluded from the overlap checks. With adequately frequent memtable flushes -- so that the tombstone gc state snapshot is refreshed -- most memtables should be excluded from overlap checks, greatly helping the cache's tombstone GC efficiency. Fixes: https://github.com/scylladb/scylladb/issues/24962 Fixes a regression introduced by https://github.com/scylladb/scylladb/pull/23255 which was backported to all releases, needs backport to all releases as well Closes scylladb/scylladb#25033 * github.com:scylladb/scylladb: docs/dev/tombstone.md: document the memtable overlap check elision optimization test/boost/row_cache_test: add test for memtable overlap check elision db/cache_mutation_reader: obtain gc-before and min-live-ts lazily mutation/mutation_compactor: use max_purgeable::can_purge and max_purgeable::purge_result db/cache_mutation_reader: use max_purgeable::can_purge() replica/table: get_max_purgeable_fn_for_cache_underlying_reader(): use max_purgable::combine() replica/database: memtable_list::get_max_purgeable(): set expiry-treshold compaction/compaction_garbage_collector: max_purgeable: add expiry_treshold replica/table: propagate gc_state to memtable_list replica/memtable_list: add tombstone_gc_state* member replica/memtable: add tombstone_gc_state_snapshot tombstone_gc: introduce tombstone_gc_state_snapshot tombstone_gc: extract shared state into shared_tombstone_gc_state tombstone_gc: per_table_history_maps::_group0_gc_time: make it a value tombstone_gc: fold get_group0_gc_time() into its caller tombstone_gc: fold get_or_create_group0_gc_time() into update_group0_refresh_time() tombstone_gc: fold get_or_create_repair_history_for_table() into update_repair_time() tombstone_gc: refactor get_or_greate_repair_history_for_table() replica/memtable_list: s/min_live_timestamp()/get_max_purgeable()/ db/read_context: return max_purgeable from get_max_purgeable() compaction/compaction_garbage_collector: add formatter for max_purgeable mutation: move definition of gc symbols to compaction.cc compaction/compaction_garbage_collector: refactor max_purgeable into a class test/boost/row_cache_test: refactor test_populating_reader_tombstone_gc_with_data_in_memtable test: rewrite test_compacting_reader_tombstone_gc_with_data_in_memtable in C++ test/boost/row_cache_test: refactor cache tombstone GC with memtable overlap tests
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.
-
We already have a copy of the Apache license in our tree, so you do not need to commit a copy of the license.
-
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.