10364fca6e
" Currently range scans build their results on the replica in the `reconcilable_result` format, that -- as its name suggests -- is normally used for reconciliation (read repair). As such this result format is quite inefficient for normal queries: it contains all columns and all tombstones in the requested range. These are all unnecessary for normal queries which only want live data and only those columns that are requested by the user. Furthermore, as the coordinator works in terms of `query::result` for normal queries anyway, this intermediate result has to be converted to the final `query::result` format adding an unnecessary intermediate conversion step. This series gets rid of this problem by introducing `query_data_on_all_shards()`, a variant of `query_mutations_on_all_shards()` that builds `query::result` directly. Reverse queries still use the old intermediate method behind the scenes. Fixes #8061 Refs #7434 Tests: unit(release, debug) " * 'range-scan-data-variant/v5-rebased' of https://github.com/denesb/scylla: cql_query_test: add unit test for the more efficient range scan result format test/cql_test_env: do_with_cql_test_env(): add thread_attributes parameter cql_query_test: test_query_limit: clean up scheduling groups storage_proxy: use query_data_on_all_shards() for data range scan queries query: partition_slice: add range_scan_data_variant option gms: add RANGE_SCAN_DATA_VARIANT cluster feature multishard_mutation_query: query_mutations_on_all_shards(): refuse reverse queries multishard_mutation_query: add query_data_on_all_shards() mutation_partition.cc: fix indentation query_result_builder: make it a public type multishard_mutation_query: generalize query code w.r.t. the result builder used multishard_mutation_query: query_mutations_on_all_shards(): extract logic into new method multishard_mutation_query: query_mutations_on_all_shards(): convert to coroutine multishar_mutation_query: do_query_mutations(): convert to coroutine multishard_mutation_query: read_page(): convert to coroutine multishard_mutation_query: extract page reading logic into separate method
Scylla
What is Scylla?
Scylla is the real-time big data database that is API-compatible with Apache Cassandra and Amazon DynamoDB. Scylla embraces a shared-nothing approach that increases throughput and storage capacity to realize order-of-magnitude performance improvements and reduce hardware costs.
For more information, please see the ScyllaDB web site.
Build Prerequisites
Scylla is fairly fussy about its build environment, requiring very recent versions of the C++20 compiler and of many libraries to build. The document HACKING.md includes detailed information on building and developing Scylla, but to get Scylla building quickly on (almost) any build machine, Scylla offers a frozen toolchain, This is a pre-configured Docker image which includes recent versions of all the required compilers, libraries and build tools. Using the frozen toolchain allows you to avoid changing anything in your build machine to meet Scylla's requirements - you just need to meet the frozen toolchain's prerequisites (mostly, Docker or Podman being available).
Building Scylla
Building Scylla with the frozen toolchain dbuild is as easy as:
$ git submodule update --init --force --recursive
$ ./tools/toolchain/dbuild ./configure.py
$ ./tools/toolchain/dbuild ninja build/release/scylla
For further information, please see:
- Developer documentation for more information on building Scylla.
- Build documentation on how to build Scylla binaries, tests, and packages.
- Docker image build documentation for information on how to build Docker images.
Running Scylla
To start Scylla server, run:
$ ./tools/toolchain/dbuild ./build/release/scylla --workdir tmp --smp 1 --developer-mode 1
This will start a Scylla node with one CPU core allocated to it and data files stored in the tmp directory.
The --developer-mode is needed to disable the various checks Scylla performs at startup to ensure the machine is configured for maximum performance (not relevant on development workstations).
Please note that you need to run Scylla with dbuild if you built it with the frozen toolchain.
For more run options, run:
$ ./tools/toolchain/dbuild ./build/release/scylla --help
Testing
See test.py manual.
Scylla APIs and compatibility
By default, Scylla is compatible with Apache Cassandra and its APIs - CQL and Thrift. There is also support for the API of Amazon DynamoDB™, which needs to be enabled and configured in order to be used. For more information on how to enable the DynamoDB™ API in Scylla, and the current compatibility of this feature as well as Scylla-specific extensions, see Alternator and Getting started with Alternator.
Documentation
Documentation can be found here. Seastar documentation can be found here. User documentation can be found here.
Training
Training material and online courses can be found at Scylla University. The courses are free, self-paced and include hands-on examples. They cover a variety of topics including Scylla data modeling, administration, architecture, basic NoSQL concepts, using drivers for application development, Scylla setup, failover, compactions, multi-datacenters and how Scylla integrates with third-party applications.
Contributing to Scylla
If you want to report a bug or submit a pull request or a patch, please read the contribution guidelines.
If you are a developer working on Scylla, please read the developer guidelines.
Contact
- The users mailing list and Slack channel are for users to discuss configuration, management, and operations of the ScyllaDB open source.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.