---
title: Limitations | Tiger Data Docs
description: Current limitations of Tiger Data products
---

While Tiger Data generally offers capabilities that go beyond what PostgreSQL offers, there are some limitations.

## Hypertable limitations

- Time dimensions (columns) used for partitioning cannot have NULL values.
- Generated columns cannot be used as partitioning dimensions. `CREATE TABLE ... WITH (tsdb.hypertable)`, `create_hypertable`, and `add_dimension` all reject columns defined with `GENERATED ALWAYS AS ... STORED`. Use a concrete column instead. If you need a derived partition key, compute and persist it in a normal column (for example in your application logic or `INSERT` statement) rather than a generated column.
- Unique indexes must include all columns that are partitioning dimensions.
- `UPDATE` statements that move values between partitions (chunks) are not supported. This includes upserts (`INSERT ... ON CONFLICT UPDATE`).
- Foreign key constraints from a hypertable referencing another hypertable are not supported.
- PostgreSQL [table inheritance](https://www.postgresql.org/docs/current/ddl-inherit.html) is not supported for hypertables and may lead to unexpected behavior.