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Malloy

malloydata.dev

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Spec score 7.6 #18 of 28 in Semantic Layer Software

What it is

Malloy is an open source language for describing data relationships and transformations. Users can define reusable calculations, table relationships and business logic in semantic models, then compile queries into SQL optimized for the connected database. The language supports nested datasets and automatically guards against common errors in 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 offers a Visual Studio Code extension for modeling, querying, transformation and visualization, plus a browser notebook through github.dev that requires a GitHub sign-in. Its Python package loads models, compiles queries and runs statements with DuckDB and BigQuery. The CLI can run Malloy files, build persistent tables and automate transformations and pipelines. The project is free and open source, with web, editor extension, API and self-hosted options, among others. DuckDB connections can disable network access; sandboxed mode also limits file access to allowed directories.

Spec sheet

Intended users
Malloy says it is immediately understandable to SQL users and easier to use and learn than SQL.Read 7 Oct 2026 · docs.malloydata.dev
Support
Malloy directs users to its Slack community to share work, ask questions, and provide feedback, and to its GitHub project for bugs and ideas.Read 7 Oct 2026 · malloydata.dev
Aggregations
Malloy reuses aggregate computations across query granularities and says this helps improve accuracy.Read 7 Oct 2026 · docs.malloydata.dev
Authoring
The VS Code extension includes schema browsing, query execution, language autocomplete, documentation, and result visualizations.Read 7 Oct 2026 · docs.malloydata.dev
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.Read 7 Oct 2026 · docs.malloydata.dev
CLI
The Malloy CLI runs Malloy files, builds persistent tables, and can automate transformations and pipelines.Read 7 Oct 2026 · docs.malloydata.dev
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.Read 7 Oct 2026 · docs.malloydata.dev
Credential security
The VS Code connection editor stores sensitive values such as passwords and tokens in the system keychain.Read 7 Oct 2026 · docs.malloydata.dev
Database integrations
The documentation lists DuckDB, MotherDuck, BigQuery, Databricks, Snowflake, PostgreSQL, MySQL, Trino, and Presto as supported databases.Read 7 Oct 2026 · docs.malloydata.dev
Editor support
Malloy provides a Visual Studio Code extension for building models, querying and transforming data, and creating visualizations.Read 7 Oct 2026 · github.com
Local data files
DuckDB support can read Parquet, CSV, and JSON files without additional setup.Read 7 Oct 2026 · docs.malloydata.dev
Nested analysis
Malloy supports nested query results, including fetching entire dashboards in a single query.Read 7 Oct 2026 · docs.malloydata.dev
Nested data
Malloy supports reading and writing nested datasets as a language feature.Read 7 Oct 2026 · docs.malloydata.dev
Python package
Malloy’s open source MIT-licensed Python package loads models, compiles queries, and runs statements, and currently works with DuckDB and BigQuery.Read 7 Oct 2026 · docs.malloydata.dev
Query execution
Malloy queries compile to SQL optimized for the connected database.Read 7 Oct 2026 · malloydata.dev
Safer aggregates
Malloy automatically prevents miscalculating aggregates such as sums, averages, and counts.Read 7 Oct 2026 · malloydata.dev
Security controls
DuckDB connections offer local and sandboxed security policies that disable network access; sandboxed mode also restricts file access to allowed directories.Read 7 Oct 2026 · docs.malloydata.dev
Semantic modeling
Malloy lets users define reusable calculations and business logic in a semantic data model.Read 7 Oct 2026 · docs.malloydata.dev
Semantic models
Malloy data models can encode reusable calculations, table relationships, and queries.Read 7 Oct 2026 · docs.malloydata.dev
SQL output
Malloy queries translate into SQL optimized for the connected database.Read 7 Oct 2026 · malloydata.dev
Visualizations
Malloy’s rendering library can use query metadata and results to render dashboards and visualizations and support drill through to detail.Read 7 Oct 2026 · docs.malloydata.dev
What it is
Malloy is an open source language for describing data relationships and transformations.Read 7 Oct 2026 · malloydata.dev

Strong points and limits

Strong points

  • Compiles queries to SQL optimized for the connected database.
  • Supports nine listed database systems.
  • DuckDB reads Parquet, CSV and JSON without extra setup.
  • DuckDB sandboxing can restrict network and file access.

Limits

  • The browser notebook requires a GitHub sign-in.
  • The downloadable CLI is not notarized on macOS.
  • The Python package currently works with DuckDB and BigQuery.

Who it suits

Malloy is aimed at people working with data models and queries, particularly SQL users whom the project says can understand it readily. It offers editor, browser, Python and CLI workflows, with connections to multiple databases.

Verdict

Malloy provides a semantic modeling language and several ways to query or automate data work. Check database support and the macOS CLI permission requirement before choosing a workflow.

Where Specifiction places it

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