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Fuse Engine

Description​

Fuse engine is the default engine for Databend, it provides a git-like interface for data management. User could query data at any point in time, and restore data to any point in time, there is a blog post about this feature: Time Travel.

Syntax​

CREATE TABLE table_name (
  column_name1 column_type1,
  column_name2 column_type2,
  ...
) [ENGINE = Fuse] [CLUSTER BY(<expr> [, <expr>, ...] )] [options];

Read more about the create table statment in ddl-create-table

Default engine​

If engine is not specified, we will default to using Engine = Fuse.

Cluster Key​

The CLUSTER BY parameter specifies the sorting method for data that consists of multiple expressions, which is useful during compaction or recluster. A suitable CLUSTER BY parameter can significantly accelerate queries.

Options​

Fuse engine support following common case-insensitive options:

  • compression = '<compression>', compression could be lz4, zstd, snappy, none. Compression method defaults to be zstd in object storage but lz4 in fs storage.

  • storage_format = '<storage_format>', storage_format could be parquet and native. Storage format defaults to be parquet in object storage but native in fs storage.

  • snapshot_loc = '<snapshot_loc>', it's a location parameter in string which could easily share a table without data copy.

  • block_size_threshold = '<block_size_threshold>', specifies the maximum data size for a file.

  • block_per_segment = '<block_per_segment>', specifies the maximum number of files that can be stored in a segment.

  • row_per_block = '<row_per_block>', specifies the maximum number of rows that can be stored in a file.

What's storage format​

By default, the storage_format is set to Parquet, which means the data is stored in Parquet format in the storage. Parquet is an open format that is suitable for cloud-native object storage and has a high compression ratio.

The storage_format also supports the Native format, which is an experimental format that primarily optimizes the additional memory copy overhead introduced when writing data to the storage. The Native format is suitable for storage devices such as file systems.