dft

dft provides two client interfaces to the DataFusion query execution engine:

1. Text User Interface (TUI): An IDE for DataFusion developers and users that provides a local database experience with utilities to analyze / benchmark queries.
2. Command Line Interface (CLI): Scriptable engine for executing queries from files.

Additionally, it provides a FlightSQL server implementation leveraging the same execution engine behind the TUI and CLI. This allows users to iterate quickly develop a database and then seamlessly deploy it.

dft is inspired by datafusion-cli, but has some differences:

1. dft TUI focuses on more complete and interactive experience for users.
2. dft contains many built in integrations such as Delta Lake, Iceberg, and MySQL (Coming Soon) that are not available in datafusion-cli.

dft TUI

The objective of dft is to provide users with the experience of having their own local database that allows them to query and join data from disparate data sources all from the terminal.

SQL & FlightSQL Editor and Results	Query History and Stats
Filterable Logs	DataFusion Session Context Details

Some of the current and planned features are:

• Tab management to provide clean and structured organization of DataFusion queries, results, and context
  • SQL editor
    • Write query results to file (TODO)
  • Query history
    • History and statistics of executed queries
  • ExecutionContext information
    • Information from ExecutionContext / Catalog / ObjectStore / State / Config
  • Logs
    • Logs from dft and DataFusion
• Custom ObjectStore Support
  • S3, Azure(TODO), GCP(TODO)
  • ObjectStore explorer. I.e. able to list files in ObjectStore
• TableProviderFactory data sources
  • Deltalake
  • Iceberg (TODO)
  • Hudi (TODO)
• Preloading DDL from ~/.config/dft/ddl.sql (or a user defined path) for local database available on startup
• Benchmarking local and FlightSQL queries with breakdown of query execution time
• "Catalog File" support - see #122
  • Save table definitions and data
  • Save parquet metadata from remote object stores

Limitations

Currently dft does not display wide result sets well (because the widget library that we use does not support horizontal scrolling - we are working with them to see what we can do about this). As a result, when working with wide data sets its best to be selective with the columns that you would like to view in the ouput.

dft CLI

The dft CLI is a scriptable interface to the tui engine for executing queries from files or the command line. The CLI is used in a similar manner to datafusion-cli but with the added benefit of supporting multiple pre-integrated data sources.

Example: Run the contents of query.sql

$ dft -f query.sql

Example: Run a query from the command line

$ dft -c "SELECT 1+2"

FlightSQL

Both of the commands above support the --flightsql parameter to run the SQL with your configured FlightSQL client. You can also configure the host used for creating FlightSQL client per command with --flightsql-host - for example --flightsql-host "http://127.0.0.1:50052".

DDL

The CLI can also run your configured DDL prior to executing the query by adding the --run-ddl parameter.

Benchmarking Queries

You can benchmark queries by adding the --bench parameter. This will run the query a configurable number of times and output a breakdown of the queries execution time with summary statistics for each component of the query (logical planning, physical planning, execution time, and total time).

Optionally you can use the --run-before param to run a query before the benchmark is run. This is useful in cases where you want to hit a temp table or write a file to disk that your benchmark query will use.

To save benchmark results to a file use the --save parameter with a file path. Further, you can use the --append parameter to append to the file instead of overwriting it.

The number of benchmark iterations is defined in your configuration (default is 10) and can be configured per benchmark run with -n parameter.

Analyze Queries

The output from EXPLAIN ANALYZE provides a wealth of information on a queries execution - however, the amount of information and connecting the dots can be difficult and manual. Further, there is detail in the MetricSet's of the underlying ExecutionPlan's that is lost in the output.

To help with this the --analyze flag can used to generate a summary of the underlying ExecutionPlan MetricSets. The summary presents the information in a way that is hopefully easier to understand and easier to draw conclusions on a query's performance.

This feature is still in it's early stages and is expected to evolve. Once it has gone through enough real world testing and it has been confirmed the metrics make sense documentation will be added on the exact calculations - until then the source will need to be inspected to see the calculations.

dft FlightSQL Server

The dft FlightSQL server (feature flag experimental-flightsql-server) is a Flight service that can be used to execute SQL queries against DataFusion. The server is started by running dft --serve and can optionally run your configured DDL with the --run-ddl parameter. Prometheus metrics can optionally be exported with the metrics feature.

This feature is experimental and does not currently implement all FlightSQL endpoints. Endpoints will be added in tandem with adding more features to the FlightSQL clients within the TUI and CLI.

User Guide

Installation

Currently, the only supported packaging is on crates.io. If you already have Rust installed it can be installed by running cargo install datafusion-tui. If rust is not installed you can download following the directions here.

Once installed you can run dft to start the application.

Internal Optional Features (Workspace Features)

dft incubates several optional features in it's crates directory. This provides us with the ability to quickly iterate on new features and test them in the main application while at the same time making it easy to export them to their own crates when they are ready.

Parquet Functions (--features=functions-parquet)

Includes functions from [datafusion-function-parquet] for querying Parquet files in DataFusion in dft. For example:

SELECT * FROM parquet_metadata('my_parquet_file.parquet')

External Optional Features (Rust Crate Features)

dft also has several external optional (conditionally compiled features) integrations which are controlled by Rust Crate Features

To build with all features, you can run

cargo install --path . --all-features

S3 (--features=s3)

Mutliple s3 ObjectStores can be registered, following the below model in your configuration file.

[[execution.object_store.s3]]
bucket_name = "my_bucket"
object_store_url = "s3://my_bucket"
aws_endpoint = "https://s3.amazonaws"
aws_access_key_id = "MY_ACCESS_KEY"
aws_secret_access_key = "MY SECRET"

[[execution.object_store.s3]]
bucket_name = "my_bucket"
object_store_url = "ny1://my_bucket"
aws_endpoint = "https://s3.amazonaws"
aws_access_key_id = "MY_ACCESS_KEY"
aws_secret_access_key = "MY SECRET"

Then you can run DDL such as

CREATE EXTERNAL TABLE my_table STORED AS PARQUET LOCATION 's3://my_bucket/table';

CREATE EXTERNAL TABLE other_table STORED AS PARQUET LOCATION 'ny1://other_bucket/table';

FlightSQL (--features=flightsql)

A separate editor for connecting to a FlightSQL server is provided.

The default connection_url is http://localhost:50051 but this can be configured your config as well:

[flightsql]
connection_url = "http://myhost:myport"

Deltalake (--features=deltalake)

Register deltalake tables. For example:

CREATE EXTERNAL TABLE table_name STORED AS DELTATABLE LOCATION 's3://bucket/table'

Json Functions (--features=function-json)

Adds functions from datafusion-function-json for querying JSON strings in DataFusion in dft. For example:

select * from foo where json_get(attributes, 'bar')::string='ham'
(show examples of using operators too)

Getting Started

To have the best experience with dft it is highly recommended to define all of your DDL in ~/.config/ddl.sql so that any tables you wish to query are available at startup. Additionally, now that DataFusion supports CREATE VIEW via sql you can also make a VIEW based on these tables.

For example, your DDL file could look like the following:

CREATE EXTERNAL TABLE users STORED AS NDJSON LOCATION 's3://bucket/users';

CREATE EXTERNAL TABLE transactions STORED AS PARQUET LOCATION 's3://bucket/transactions';

CREATE EXTERNAL TABLE listings STORED AS PARQUET LOCATION 'file://folder/listings';

CREATE VIEW OR REPLACE users_listings AS SELECT * FROM users LEFT JOIN listings USING (user_id);

This would make the tables users, transactions, listings, and the view users_listings available at startup. Any of these DDL statements could also be run interactively from the SQL editor as well to create the tables.

Key Mappings

The interface is split into several tabs and modes so that relevant information can be viewed and controlled in a clean and organized manner. When not writing a SQL query keys can be entered to navigate and control the interface.

SQL Tab

Editor for executing SQL with local DataFusion SessionContext.

• Normal mode
  • Not editable
    • q => quit datafusion-tui
    • e => start editing SQL Editor in Edit mode
    • c => clear contents of SQL Editor
    • Enter => execute query
    • Enter the tab number in brackets after a tabs name to navigate to that tab
    • If query results are longer or wider than screen, you can use arrow keys to scroll
  • Editable
    • Character keys to write queries
    • Backspace / tab / enter work same as normal
    • Shift + Up/Down/Left/Right => Select text
    • Alt + Enter => execute query
    • esc to exit Edit mode and go back to Normal mode
• DDL mode
  • Not editable
    • l => load configured DDL file into editor
    • enter => rerun configured DDL file
    • s => write editor contents to configured DDL file
  • Editable
    • Character keys to write queries
    • Backspace / tab / enter work same as normal
    • Shift + Up/Down/Left/Right => Select text
    • Alt + Enter => execute query
    • esc to exit Edit mode and go back to Normal mode

FlightSQL Tab

Same interface as SQL tab but sends SQL queries to FlightSQL server.

• Normal mode
  • q => quit datafusion-tui
  • e => start editing SQL Editor in Edit mode
  • c => clear contents of SQL Editor
  • Enter => execute query
  • Enter the tab number in brackets after a tabs name to navigate to that tab
  • If query results are longer or wider than screen, you can use arrow keys to scroll
  • Edit mode
    • Character keys to write queries
    • Backspace / tab / enter work same as normal
    • Shift + Up/Down/Left/Right => Select text
    • Alt + Enter => execute query
    • esc to exit Edit mode and go back to Normal mode

History Tab

TODO

Logs Tab

• Logging mode (coming from tui_logger)
  • h => Toggles target selector widget hidden/visible
  • f => Toggle focus on the selected target only
  • UP => Select previous target in target selector widget
  • DOWN => Select next target in target selector widget
  • LEFT => Reduce SHOWN (!) log messages by one level
  • RIGHT => Increase SHOWN (!) log messages by one level
  • - => Reduce CAPTURED (!) log messages by one level
  • + => Increase CAPTURED (!) log messages by one level
  • PAGEUP => Enter Page Mode and scroll approx. half page up in log history.
  • PAGEDOWN => Only in page mode: scroll 10 events down in log history.
  • ESCAPE => Exit page mode and go back to scrolling mode
  • SPACE => Toggles hiding of targets, which have logfilter set to off

Config Reference

The dft configuration is stored in ~/.config/dft/config.toml. All configuration options are listed below.

Execution Config

The execution config is where you can define query execution properties. You can configure the ObjectStores that you want to use in your queries and path of a DDL file that you want to run on startup. For example, if you have an S3 bucket you want to query you could define it like so:

[[execution.object_store.s3]]
bucket_name = "my_bucket"
object_store_url = "s3://my_bucket"
aws_endpoint = "https://s3.amazonaws"
aws_access_key_id = "MY_ACCESS_KEY"
aws_secret = "MY SECRET"
aws_session_token = "MY_SESSION"
aws_allow_http = false

And define a custom DDL path like so (the default is ~/.config/dft/ddl.sql).

[execution]
ddl_path = "/path/to/my/ddl.sql"

Multiple ObjectStores can be defined in the config file. In the future datafusion SessionContext and SessionState options can be configured here.

Set the number of iterations for benchmarking queries (10 is the default).

[execution]
benchmark_iterations = 10

The batch size for query execution can be configured based on the app being used (TUI, CLI, or FlightSQL Server). For the TUI it defaults to 100, which may slow down queries, because a Record Batch is used as a unit of pagination and too many rows can cause the TUI to hang. For the CLI and FlightSQL Server, the default is 8092.

[execution]
cli_batch_size = 8092
tui_batch_size = 100
flightsql_server_batch_size = 8092

Display Config

The display config is where you can define the frame rate of the TUI.

[display]
frame_rate = 60

Interaction Config

The interaction config is where mouse and paste behavior can be defined. This is not currently implemented.

[interaction]
mouse = true
paste = true

FlightSQL Config

The FlightSQL config is where you can define the connection URL for the FlightSQL server.

[flightsql]
connection_url = "http://localhost:50051"
server_metrics_port = "0.0.0.0:9000"

Editor Config

The editor config is where you can set your preferred editor settings.

Currently only syntax highlighting is supported. It is experimental because currently the regex that is used to determine keywords only works in simple cases.

[editor]
experimental_syntax_highlighting = true