Malloy

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What Malloy is

Malloy is an open source language for describing data relationships and transformations. Its semantic models can define reusable calculations, business logic, table relationships, and queries. Malloy queries compile into SQL optimized for the connected database. The language supports nested datasets and automatically guards against common aggregate miscalculations involving sums, averages, and counts. Supported databases include DuckDB, MotherDuck, BigQuery, Databricks, Snowflake, PostgreSQL, MySQL, Trino, and Presto. DuckDB can read Parquet, CSV, and JSON files without additional setup. Malloy provides a Visual Studio Code extension for modeling, querying, transforming data, and creating visualizations; a browser notebook through github.dev requires a GitHub sign-in. Its Python package loads models, compiles queries, and runs statements with DuckDB and BigQuery. The CLI runs Malloy files, builds persistent tables, and can automate transformations and pipelines. DuckDB connections can disable network access, and sandboxed mode also limits file access to allowed directories. The CLI binary is not currently notarized on macOS and requires explicit permission in Privacy and Security settings. Malloy is free and open source; its project points users to Slack and GitHub Issues for community help and reports.

Who it suits

Malloy suits SQL users who want reusable semantic models and query workflows across supported databases. Its documentation describes it as immediately understandable to SQL users and easier to learn than SQL.

What it does well

Compiles queries into SQL optimized for connected databases
Supports nine listed database systems
DuckDB reads Parquet, CSV, and JSON without extra setup
VS Code extension includes query and visualization tools

What to know first

Browser notebook requires GitHub sign-in
macOS CLI binary is not notarized
Sandboxed DuckDB mode restricts file access to allowed directories

Limits

The Python package currently works with DuckDB and BigQuery. The downloadable CLI binary is not notarized on macOS and requires explicit permission in macOS Privacy and Security settings.

Getting started

Visit the Malloy website.
Choose a supported database, such as DuckDB or BigQuery.
Use the Visual Studio Code extension to browse schemas and build models.
For browser-based notebook use, open it through github.dev and sign in to GitHub.
Use the Python package with DuckDB or BigQuery, or run Malloy files with the CLI.

Verdict

Malloy combines semantic modeling with database-specific SQL generation and several authoring options. macOS CLI users should account for the required permission step, while browser notebook users need a GitHub sign-in.

Questions

Is Malloy free?

Yes. Malloy is free and open source, and its Python package is MIT-licensed.

Which databases does Malloy support?

The documentation lists DuckDB, MotherDuck, BigQuery, Databricks, Snowflake, PostgreSQL, MySQL, Trino, and Presto.

Can I use Malloy in a browser?

Yes. A browser-based notebook is available through github.dev and requires a GitHub sign-in.

What does the VS Code extension include?

It includes schema browsing, query execution, autocomplete, documentation, and result visualizations.

Can Malloy query local data files?

DuckDB support can read Parquet, CSV, and JSON files without additional setup.

Does Malloy offer a Python package and CLI?

Yes. The Python package loads models, compiles queries, and runs statements with DuckDB and BigQuery. The CLI runs Malloy files, builds persistent tables, and automates transformations and pipelines.

Facts from Malloy's own pages

Aggregations: Malloy reuses aggregate computations across query granularities and says this helps improve accuracy. · docs.malloydata.dev, 7 Oct 2026
Authoring: The VS Code extension includes schema browsing, query execution, language autocomplete, documentation, and result visualizations. · docs.malloydata.dev, 7 Oct 2026
Browser use: The Malloy extension works in VS Code Web, where it supports DuckDB with local CSV, JSON, and Parquet files; BigQuery, Snowflake, and PostgreSQL require VS Code Desktop. · docs.malloydata.dev, 7 Oct 2026
CLI: The Malloy CLI runs Malloy files, builds persistent tables, and can automate transformations and pipelines. · docs.malloydata.dev, 7 Oct 2026
CLI limitation: Malloy states that its downloadable CLI binary is currently not notarized on macOS and requires explicit permission in macOS Privacy and Security settings. · docs.malloydata.dev, 7 Oct 2026
Credential security: The VS Code connection editor stores sensitive values such as passwords and tokens in the system keychain. · docs.malloydata.dev, 7 Oct 2026
Database integrations: The documentation lists DuckDB, MotherDuck, BigQuery, Databricks, Snowflake, PostgreSQL, MySQL, Trino, and Presto as supported databases. · docs.malloydata.dev, 7 Oct 2026
Editor support: Malloy provides a Visual Studio Code extension for building models, querying and transforming data, and creating visualizations. · github.com, 7 Oct 2026
Intended users: Malloy says it is immediately understandable to SQL users and easier to use and learn than SQL. · docs.malloydata.dev, 7 Oct 2026
Local data files: DuckDB support can read Parquet, CSV, and JSON files without additional setup. · docs.malloydata.dev, 7 Oct 2026
Nested analysis: Malloy supports nested query results, including fetching entire dashboards in a single query. · docs.malloydata.dev, 7 Oct 2026
Nested data: Malloy supports reading and writing nested datasets as a language feature. · docs.malloydata.dev, 7 Oct 2026
Python package: Malloy’s open source MIT-licensed Python package loads models, compiles queries, and runs statements, and currently works with DuckDB and BigQuery. · docs.malloydata.dev, 7 Oct 2026
Query execution: Malloy queries compile to SQL optimized for the connected database. · malloydata.dev, 7 Oct 2026
Safer aggregates: Malloy automatically prevents miscalculating aggregates such as sums, averages, and counts. · malloydata.dev, 7 Oct 2026
Security controls: DuckDB connections offer local and sandboxed security policies that disable network access; sandboxed mode also restricts file access to allowed directories. · docs.malloydata.dev, 7 Oct 2026
Semantic modeling: Malloy lets users define reusable calculations and business logic in a semantic data model. · docs.malloydata.dev, 7 Oct 2026
Semantic models: Malloy data models can encode reusable calculations, table relationships, and queries. · docs.malloydata.dev, 7 Oct 2026
SQL output: Malloy queries translate into SQL optimized for the connected database. · malloydata.dev, 7 Oct 2026
Support: The project directs users to its Slack community to ask questions and share models, and to GitHub Issues for bug reports and feature requests. · github.com, 7 Oct 2026
Visualizations: Malloy’s rendering library can use query metadata and results to render dashboards and visualizations and support drill through to detail. · docs.malloydata.dev, 7 Oct 2026
What it is: Malloy is an open source language for describing data relationships and transformations. · malloydata.dev, 7 Oct 2026

Where Malloy stands on Freedom251

Semantic Layer Software#5 of 28
Data Transformation Tools#24 of 37