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Jailer is a tool for database subsetting, schema and data browsing.

It creates small slices from your database and lets you navigate through your database following the relationships..
Ideal for creating small samples of test data or for local problem analysis with relevant production data.


Features

  • The Data Browser lets you navigate through your database following the relationships (foreign key-based or user-defined) between tables.

  • The Subsetter creates small slices from your productive database and imports the data into your development and test environment (consistent and referentially intact).

  • Improves database performance by removing and archiving obsolete data without violating integrity.

  • Generates SQL (topologically sorted), JSON, YAML, XML (hierarchically structured) and DbUnit datasets.

  • AI Assistant

    • Subsetting: Describe in natural language what data to subset. The AI generates the subject table, WHERE condition, and association restrictions.
    • 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 queries - suggestions menu, split SQL / explanation view, inline diff.
        

  • SQL Console Chart: instantly turn query results into interactive charts - 11 chart types, extensive customization, export as PNG / JPEG / SVG.

  • A demo database is included with which you can get a first impression without any configuration effort.


Supported Databases

Any DMBS is basically supported thanks to the JDBC technology used.
Jailer also uses additional knowledge to cope with the peculiarities of major database systems. These are:

  • PostgreSQL
  • Oracle
  • MySQL
  • MariaDB
  • Microsoft SQL Server
  • IBM Db2
  • SQLite
  • Sybase
  • Amazon Redshift
  • Firebird
  • Informix Dynamic Server
  • H2
  • HSQL (HyperSQL)
  • Derby
  • Interbase
  • Exasol
  • SAP HANA
  • Vertica
  • Snowflake
  • ClickHouse
                    

News

2026-08-25   Discover Associations: Reverse-engineer the data model of a database that has no foreign key constraints. Candidates are derived from the column names and, optionally, from the data itself. Each one is verified against the database and rated with a confidence.
2026-08-21   Mermaid ER diagram: The data model can now be exported as a Mermaid erDiagram - either the whole model or only the tables visible in the graphical view. Unlike an image this is plain text, so it can be embedded into Markdown documents, READMEs or wikis and put under version control. "Export graph as image..." now offers SVG as well, and the command line command render-mermaid writes the same diagram in a build pipeline.
2026-08-19   Path Finder: Candidate tables now show a confidence estimate of how likely they belong on the path, based on how specific a table is compared to the other candidates at the same distance, and they can be sorted by it.
2026-07-31   BLOB/CLOB content preview: The detected content type and an image thumbnail are shown directly in the cells of the result tables of the Data Browser and the SQL Console. The content viewer renders images (including SVG), text with syntax highlighting, PDF documents with page navigation and zoom, ZIP archives as an entry list, and anything else as a hexadecimal dump. Compressed single-file contents are shown decompressed.
2026-07-16   Spatial data preview: Geometry and geography values are shown on an interactive map over OpenStreetMap tiles - in the cell preview of the Data Browser and as a map overlay on the result of the SQL Console, where the geometries can be colored by the values of a column. Supports PostGIS, Oracle, SQL Server and MySQL/MariaDB. Export now reconstructs spatial values with a dialect-specific SQL expression instead of losing the type information.
2026-06-25   AI Subsetting Assistant: Describe in natural language what data to subset. The AI generates the subject table, WHERE condition, and association restrictions.
2026-06-17   Chart tab: The SQL Console turns query results into interactive charts - directly in the result view. 11 chart types including 2D and 3D variants, with color schemes, transparency, aggregation, axis scaling and data labels. Charts can be exported as PNG, JPEG or SVG.
2026-05-31   SQL Advisor: Analyze, explain, and refactor existing SQL queries with AI assistance - suggestions menu, split SQL / explanation view, and inline diff highlighting.
2026-06-01   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 .
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.
2017-03-30   Improved filter management . Filter 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.
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.
2016-04-15   A Data Browser    has been introduced. Navigate bidirectionally through the database by following foreign-key-based or user-defined relationships.


About Jailer

Databases are growing in both size and complexity to meet the increasing demands of business. Applications to process the data are also increasing in size and complexity. With the growing complexity, solid testing becomes more and more important in order to assure the quality of software. Ideally we would like to test all changes against up-to-date production data, so the general practice is use a copy of the production database for all testing.

But when a database exceeds a certain size it becomes very expensive to provide full-size copies of the production database for development and testing. One solution of this problem is to have fewer full size copies of the production database than are really needed, often only one, which will be shared between the development and testing teams.

Of course this is far from optimal. Data in the database is left in an unknown state when passed from one team to the other. It takes a long time to provide a refresh of the production copy when it's required. Always having an up-to-date production copy is almost impossible.

The databases required for development and testing rarely need to be full size, it is often easier to work on a small copy. Unfortunately it is very hard to manually extract a small subset of the production data. It is not possible to just take 10% of each table to get a 10% size database. The data in one table would not be related to the data in the other tables. It would not be referentially intact.

Jailer simplifies the extraction of referentially intact data. Once you have defined an extraction model, it can be used to extract data from the production database fast and easy whenever up-to-date test data is required.