External Catalogs
External catalogs connect your existing systems to Altertable, making them queryable alongside your Altertable catalogs and other data sources.
All external catalogs support federated queries, allowing you to join data from multiple sources in a single SQL query. Learn more about authentication and how to access your credentials.
Common external catalog patterns include:
- Database and warehouse catalogs for Postgres, MySQL, MariaDB, ClickHouse, BigQuery, Snowflake, Redshift, Supabase, and DuckDB.
- Bucket Tables for files that already live in a connected bucket, with table names mapped to path prefixes.
- Iceberg Tables for Iceberg datasets whose metadata and data files already live in a connected bucket.
- Iceberg REST catalogs for catalogs managed by Cloudflare R2 Data Catalog, Amazon S3 Tables, or AWS Glue.
Bucket Tables support Parquet, CSV, and JSON files. Hive-style partitioned paths are also supported, so partition keys can be queried as columns.
Iceberg Tables let you expose existing Iceberg datasets in the lakehouse without copying them into a separate managed catalog. You choose the bucket, then map logical table names to Iceberg roots.
DuckDB catalogs expose a .duckdb file that already lives in a connected bucket. They are read-only in Altertable and work best when another process owns the file.
Iceberg REST catalog connections use the same Iceberg query path but connect to an external catalog service instead of a bucket path:
Catalog | Required settings |
|---|---|
R2 Data Catalog | Warehouse name, catalog URI, and token |
S3 Tables | Table bucket ARN, region, access key ID, and secret access key |
AWS Glue | AWS account ID, region, and role ARN |
For network-restricted database-style catalogs, Altertable can also connect through an SSH tunnel. Configure the bastion host while creating the catalog, then copy the generated public key from the catalog details page into the SSH server's authorized_keys.