GitHub - Wisser/Jailer: Database Subsetting and Relationa...

Jailer is a tool for database subsetting and relational data browsing.

The Subsetter creates small slices from your database (consistent and referentially intact) as SQL (topologically sorted), DbUnit records or XML.

Ideal for creating small samples of test data or for local problem analysis with relevant production data.
The Data Browser lets you navigate through your database following the relationships (foreign key-based or user-defined) between tables.

DataBrowser.mp4

Features

Exports consistent and referentially intact row-sets from your productive database and imports the data into your development and test environment.
Improves database performance by removing and archiving obsolete data without violating integrity.
Generates topologically sorted SQL-DML, hierarchically structured JSON, YAML, XML and DbUnit datasets.
Data Browsing. Navigate bidirectionally through the database by following foreign-key-based or user-defined relationships.
SQL Console with code completion, syntax highlighting and database metadata visualization.
AI Query Assistant. Generate SQL from natural language questions using Anthropic or OpenAI-compatible APIs with smart table selection for large schemas.
SQL Advisor. Analyze, explain, and refactor existing SQL queries with AI assistance - inline diff view shows exactly what changed.
A demo database is included with which you can get a first impression without any configuration effort.

Supported Databases

Thanks to the JDBC technology used, any DMBS is in principle supported. For best results, specific additional support features are useful, however. These are available for:

PostgreSQL
Oracle
MySQL
MariaDB
Microsoft SQL Server
IBM Db2
SQLite
Sybase
Amazon Redshift
Firebird
Informix Dynamic Server
H2
Exasol

News

2026-05-31 SQL Advisor: Analyze, explain, and refactor existing SQL queries with AI assistance. A suggestions menu covers the most common tasks (explain, optimize, rewrite as CTEs, find NULL issues, and more). Results are shown as a split view with the revised SQL on the left and a formatted explanation on the right. An inline diff toggle highlights removed and added lines directly in the SQL area.
2026-05-15 AI Query Assistant: Generate SQL from natural language questions using Anthropic or OpenAI-compatible APIs (OpenAI, Azure, Groq, Ollama, OpenRouter, etc.) with smart table selection for large schemas.
2024-07-04 Data can now also be exported as structured JSON and YAML files.
2024-06-26 A dark UI theme has been introduced that improves readability in low light environments.
2024-04-18 DDL scripts for creating database objects can now be generated thanks to an integration of the Liquibase tool. This makes it possible to create subset databases from scratch using only on-board means.
2023-02-03 Thanks to deep analysis of statements, the SQL console can now relate the result of queries to the source tables and display them accordingly. In addition, this technique also allows filter conditions to be dynamically added to arbitrary SQL queries.
2022-01-01 Comprehensive redesign and modernization of the entire user interface. New Look & Feel FlatLaf.
2021-02-04 Cycles in parent-child relationships will be detected and broken. Thus, such data can be exported by deferring the insertion of nullable foreign keys.
2020-02-04 The Jailer engine is published in Maven repository. https://mvnrepository.com/artifact/io.github.wisser/jailer-engine
2019-02-01 The new "Model Migration Tool" allows you to easily find and edit the newly added associations if the data model has been extended after the last change to this extraction model.
2018-04-26 The new feature "Analyze SQL" analyzes SQL statements and proposes association definitions. This allows to reverse-engineer the data model based on existing SQL queries.
2018-03-06 SQL Console with code completion, syntax highlighting and database metadata visualization.
2017-05-10 New API provides programmatic access to the data export and import functionality. https://wisser.github.io/Jailer/api.html
2017-03-30 Improved filter management. Templates allows you to define rules for assigning filters to columns. Filters on primary key columns will automatically be propagated to the corresponding foreign key columns. https://wisser.github.io/Jailer/filters.html
2016-12-04 Data can now also be exported directly to a schema of the same database. This ensures optimal performance.
2016-10-23 Rows can alternatively be collected in a separate embedded database. This allows exporting data from read-only databases.
2016-07-20 Implemented the "Subset by Example" feature: Use the Data Browser to collect all the rows to be extracted and let Jailer create a model for that subset. https://wisser.github.io/Jailer/subset-by-example.html
2016-04-15 A Data Browser has been introduced. Navigate bidirectionally through the database by following foreign-key-based or user-defined relationships.

Installation

Use the installation file "Jailer-database-tools-n.n.n.msi" (for Windows) or "jailer-database-tools_n.n.n-x64.deb" (for Linux).

Unless you want to use your own Java installation. Or also if you want to use the command line interface (CLI). In this cases unzip the file "jailer_n.n.n.zip". See also https://wisser.github.io/Jailer/faq.html#multiuser

To start the tool from the unpacked zip:

On windows platform execute "Jailer.exe". You can also start "jailerGUI.bat".
On Unix/Linux/macOS platform execute the script "jailerGUI.sh" or use "java -jar jailer.jar"