TiFlash

TiFlash is a columnar storage component of TiDB and TiDB Cloud, the fully-managed service of TiDB. It mainly plays the role of Analytical Processing (AP) in the Hybrid Transactional/Analytical Processing (HTAP) architecture of TiDB.

TiFlash stores data in columnar format and synchronizes data updates in real-time from TiKV by Raft logs with sub-second latency. Reads in TiFlash are guaranteed transactionally consistent with Snapshot Isolation level. TiFlash utilizes Massively Parallel Processing (MPP) computing architecture to accelerate the analytical workloads.

TiFlash repository is based on ClickHouse. We appreciate the excellent work of the ClickHouse team.

Quick Start

Start with TiDB Cloud

Quickly explore TiFlash with a free trial of TiDB Cloud.

See TiDB Cloud Quick Start Guide.

Start with TiDB

See Quick Start with HTAP and Use TiFlash.

Build TiFlash

TiFlash can be built on the following hardware architectures:

• x86-64 / amd64
• aarch64

And the following operating systems:

• Linux
• MacOS

1. Prepare Prerequisites

The following packages are required:

• CMake 3.23.0+
• Clang 17.0.0+ under Linux or AppleClang 14.0.0+ under MacOS
• Rust
• Python 3.0+
• Ninja-Build or GNU Make
• Ccache (not necessary but highly recommended to reduce rebuild time)

Detailed steps for each platform are listed below.

2. Checkout Source Code

git clone https://github.com/pingcap/tiflash.git --recursive -j 20
cd tiflash

3. Build

To build TiFlash for development:

# In the TiFlash repository root:
cmake --workflow --preset dev

Note: In Linux, usually you need to explicitly specify to use LLVM.

export CC="/usr/bin/clang-17"
export CXX="/usr/bin/clang++-17"

In MacOS, if you install llvm clang, you need to explicitly specify to use llvm clang.

Add the following lines to your shell environment, e.g. ~/.bash_profile.

export PATH="/opt/homebrew/opt/llvm/bin:$PATH"
export CC="/opt/homebrew/opt/llvm/bin/clang"
export CXX="/opt/homebrew/opt/llvm/bin/clang++"

Or use CMAKE_C_COMPILER and CMAKE_CXX_COMPILER to specify the compiler, like this:

mkdir cmake-build-debug
cd cmake-build-debug

cmake .. -GNinja -DCMAKE_BUILD_TYPE=DEBUG -DCMAKE_C_COMPILER=/opt/homebrew/opt/llvm/bin/clang -DCMAKE_CXX_COMPILER=/opt/homebrew/opt/llvm/bin/clang++

ninja tiflash

After building, you can get TiFlash binary in dbms/src/Server/tiflash in the cmake-build-debug directory.

Build Options

TiFlash has several CMake build options to tweak for development purposes. These options SHOULD NOT be changed for production usage, as they may introduce unexpected build errors and unpredictable runtime behaviors.

To tweak options, pass one or multiple -D...=... args when invoking CMake, for example:

cd cmake-build-debug
cmake .. -GNinja -DCMAKE_BUILD_TYPE=DEBUG -DFOO=BAR
                                          ^^^^^^^^^

• Build Type:

  • -DCMAKE_BUILD_TYPE=RELWITHDEBINFO: Release build with debug info (default)

  • -DCMAKE_BUILD_TYPE=DEBUG: Debug build

  • -DCMAKE_BUILD_TYPE=RELEASE: Release build

  Usually you may want to use different build directories for different build types, e.g. a new build directory named cmake-build-release for the release build, so that compile unit cache will not be invalidated when you switch between different build types.

• Build with Unit Tests:

  • -DENABLE_TESTS=ON: Enable unit tests (enabled by default in debug profile)

  • -DENABLE_TESTS=OFF: Disable unit tests (default in release profile)

• Build using GNU Make instead of ninja-build:

  Click to expand instructions

  To use GNU Make, simply don't pass `-GNinja` to cmake: ```shell cd cmake-build-debug cmake .. -DCMAKE_BUILD_TYPE=DEBUG make tiflash -j ``` > **NOTE**: Option `-j` (defaults to your system CPU core count, otherwise you can optionally specify a number) is used to control the build parallelism. Higher parallelism consumes more memory. If you encounter compiler OOM or hang, try to lower the parallelism by specifying a reasonable number, e.g., half of your system CPU core count or even smaller, after `-j`, depending on the available memory in your system.

• Build with System Libraries:

  Click to expand instructions

  For local development, it is sometimes handy to use pre-installed third-party libraries in the system, rather than to compile them from sources of the bundled (internal) submodules. Options are supplied to control whether to use internal third-party libraries (bundled in TiFlash) or to try using the pre-installed system ones. > **WARNING**: It is NOT guaranteed that TiFlash would still build if any of the system libraries are used. > Build errors are very likely to happen, almost all the time. You can view these options along with their descriptions by running: ```shell cd cmake-build-debug cmake -LH | grep "USE_INTERNAL" -A3 ``` All of these options are default as `ON`, as the names tell, using the internal libraries and build from sources. There is another option to append extra paths for CMake to find system libraries: - `PREBUILT_LIBS_ROOT`: Default as empty, can be specified with multiple values, separated by `;`

• Build for AMD64 Architecture:

  Click to expand instructions

  To deploy TiFlash under the Linux AMD64 architecture, the CPU must support the `AVX2` instruction set. Ensure that `cat /proc/cpuinfo | grep avx2` has output. If need to build TiFlash for AMD64 architecture without such instruction set, please use cmake option `-DNO_AVX_OR_HIGHER=ON`.

Run Unit Tests

Unit tests are automatically enabled in debug profile. To build these unit tests:

# In the TiFlash repository root:
cmake --workflow --preset unit-tests-all

Then, to run these unit tests:

cd cmake-build-debug
./dbms/gtests_dbms
./libs/libdaemon/src/tests/gtests_libdaemon
./libs/libcommon/src/tests/gtests_libcommon

More usages are available via ./dbms/gtests_dbms --help.

Run Sanitizer Tests

TiFlash supports testing with thread sanitizer and address sanitizer.

To build unit test executables with sanitizer enabled:

# In the TiFlash repository root:
cmake --workflow --preset asan-tests-all # or tsan-tests-all

There are known false positives reported from leak sanitizer (which is included in address sanitizer). To suppress these errors, set the following environment variables before running the executables:

LSAN_OPTIONS="suppressions=tests/sanitize/asan.suppression" ./dbms/gtests_dbms ...
# or
TSAN_OPTIONS="suppressions=tests/sanitize/tsan.suppression" ./dbms/gtests_dbms ...

Run Integration Tests

Check out the Integration Test Guide for more details.

Run MicroBenchmark Tests

To build micro benchmark tests, you need release profile and tests enabled:

# In the TiFlash repository root:
cmake --workflow --preset benchmarks

Then, to run these micro benchmarks:

cd cmake-build-release
./dbms/bench_dbms

# Or run with filter:
# ./dbms/bench_dbms --benchmark_filter=xxx

More usages are available via ./dbms/bench_dbms --help.

Generate LLVM Coverage Report

To build coverage report, run the script under release-centos7-llvm

cd release-centos7-llvm
./gen_coverage.sh
# Or run with filter:
# FILTER='*DMFile*:*DeltaMerge*:*Segment*' ./gen_coverage.sh

# After the script finished, it will output the directory of code coverage report, you can check out the files by webbrowser
python3 -m http.server --directory "${REPORT_DIR}" "${REPORT_HTTP_PORT}"

Contributing

Here is the overview of TiFlash architecture The architecture of TiFlash's distributed storage engine and transaction layer.

See TiFlash Development Guide and TiFlash Design documents.

Before submitting a pull request, please resolve clang-tidy errors and use format-diff.py to format source code, otherwise CI build may raise error.

NOTE: It is required to use clang-format 17.0.0+.

# In the TiFlash repository root:
merge_base=$(git merge-base upstream/master HEAD)
python3 release-centos7-llvm/scripts/run-clang-tidy.py -p cmake-build-debug -j 20 --files `git diff $merge_base --name-only`
# if there are too much errors, you can try to run the script again with `-fix`
python3 format-diff.py --diff_from $merge_base

License

TiFlash is under the Apache 2.0 license. See the LICENSE file for details.