7c2b1ea0b5
`system.view_building_tasks` is a single-partition Raft group0 table (pk = `"view_building"`, CK = timeuuid). When `clean_finished_tasks()` deletes hundreds of finished tasks, the physical rows remain in SSTables until compaction. Any subsequent read of the partition counts every column of every tombstoned row as a dead cell, triggering `tombstone_warn_threshold` warnings in large clusters. Two-part fix: **1. Range tombstones instead of row tombstones (commits 2–3)** Instead of one row tombstone per finished task, find the minimum alive task UUID (`min_alive_uuid`) and emit a single range tombstone `[before_all, min_alive_uuid)` covering all tasks below that boundary. This reduces the tombstone count significantly and also benefits future compaction. **2. Bounded scan with `min_task_id` (commits 4–6)** Even with range tombstones, physical rows remain until compaction and still count as dead cells during reads. The only way to avoid them is to not read them at all. - Add a `min_task_id timeuuid` static column to `system.view_building_tasks`. - On every GC, write `min_task_id = min_alive_uuid` atomically with the range tombstone (same Raft batch). - On reload, read `min_task_id` first using a **static-only partition slice** (empty `_row_ranges` + `always_return_static_content`): the SSTable reader stops immediately after the static row before processing any clustering tombstones — zero dead cells counted. - Use `AND id >= min_task_id` as a lower bound for the main task scan, skipping all tombstoned rows. The static-only read and the bounded scan are gated on the `VIEW_BUILDING_TASKS_MIN_TASK_ID` cluster feature so mixed-version clusters fall back to the full scan. The issue is not critical, so the fix shouldn't be backported. Fixes SCYLLADB-657 Closes scylladb/scylladb#28929 * github.com:scylladb/scylladb: test/cluster/test_view_building_coordinator: add reproducer for tombstone threshold warning docs: document tombstone avoidance in view_building_tasks view_building: add `task_uuid_generator` to `view_building_task_mutation_builder` view_building: introduce `task_uuid_generator` view_building: store `min_alive_uuid` in view building state view_building: set min_task_id when GC-ing finished tasks view_building: add min_task_id support to view_building_task_mutation_builder view_building: add min_task_id static column and bounded scan to system_keyspace view_building: use range tombstone when GC-ing finished tasks view_building: add range tombstone support to view_building_task_mutation_builder view_building: introduce VIEW_BUILDING_TASKS_MIN_TASK_ID cluster feature
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 previewin thedocs/directory to 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
-
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.