Catalog

TL;DR With the open table format wars largely settled, the strategic fight in 2026 has moved up to the catalog layer - the system that manages tables, namespaces, governance, and access. Four credible open or open-ish catalogs are now in serious play: Unity Catalog (Databricks), Polaris (Snowflake), Apache Gravitino (Datastrato/community), and Project Nessie (Dremio/community). All four implement the Iceberg REST catalog spec to varying degrees, which means clients can talk to them through a common protocol. The differentiation has moved to governance, multi-tenancy, lineage, federation, and developer experience. Unity is the most production-mature and the most coupled to Databricks. Polaris is the cleanest open implementation of the REST spec. Gravitino is the most ambitious in scope - aiming to catalog non-table assets too. Nessie is the most opinionated about Git-style branching for data. The winning catalog will probably not be a single project. It will be the protocol (Iceberg REST) plus multiple compliant implementations plus federation between them. That is the picture 2026 ends with. Why The Catalog Layer Matters Now A table format defines how data is laid out on disk. A catalog defines: ...

In 2023, the question was “which open table format will survive - Iceberg, Delta, or Hudi?” In 2026, that debate is over. Apache Iceberg won, and it won for reasons that have almost nothing to do with its raw performance. It won because it is the only format that both Snowflake and Databricks now treat as a first-class citizen, because the vendors picked sides on catalogs rather than table formats, and because enterprise buyers decided that multi-engine portability was worth more than a small performance edge. ...