docs/content/concepts/views.md

---
title: "Views"
weight: 10
type: docs
aliases:
- /concepts/views.html
---
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# Views

A view is a logical table that encapsulates business logic and domain-specific semantics.
While most compute engines support views natively, each engine stores view metadata in proprietary formats, creating interoperability challenges across different platforms.
Paimon views abstracting engine-specific query dialects and establishing unified metadata standards.
View metadata could enable centralized view management that facilitates cross-engine sharing and reduces maintenance complexity in heterogeneous computing environments.

## Catalog support

View metadata is persisted only when the catalog implementation supports it:

- **Hive metastore catalog** – view metadata is stored together with table metadata inside the
  metastore warehouse.
- **REST catalog** – view metadata is kept in the REST backend and exposed through the catalog API.

File-system catalogs do not currently support views because they lack persistent metadata storage.


### Representation structure

| Field     | Type | Description |
|-----------|------|-------------|
| `query`   | `string` | Canonical SQL `SELECT` statement that defines the view. |
| `dialect` | `string` | SQL dialect identifier (for example, `spark` or `flink`). |

Multiple representations can be stored for the same version so that different engines can access the
view using their native dialect.

## Operations

### Create or replace view

Use `CREATE VIEW` or `CREATE OR REPLACE VIEW` to register a view. Paimon assigns a UUID, writes the
first metadata file, and records version `1`.

```sql
CREATE VIEW sales_view AS
SELECT region, SUM(amount) AS total_amount
FROM sales
GROUP BY region;
```

### Alter view dialect via procedure

Paimon provides the `sys.alter_view_dialect` procedure so that engines can manage multiple SQL
representations for the same view version.

#### Flink example

```sql
-- Add a Flink dialect
CALL [catalog.]sys.alter_view_dialect('view_identifier', 'add', 'flink', 'SELECT ...');

-- Update the stored Flink dialect
CALL [catalog.]sys.alter_view_dialect('view_identifier', 'update', 'flink', 'SELECT ...');

-- Drop the Flink dialect representation
CALL [catalog.]sys.alter_view_dialect('view_identifier', 'drop', 'flink');
```

#### Spark example

```sql
-- Add a Spark dialect
CALL sys.alter_view_dialect('view_identifier', 'add', 'spark', 'SELECT ...');

-- Update the Spark dialect
CALL sys.alter_view_dialect('view_identifier', 'update', 'spark', 'SELECT ...');

-- Drop the Spark dialect
CALL sys.alter_view_dialect('view_identifier', 'drop', 'spark');
```

### Drop view

`DROP VIEW view_name;`

## See also

- [Spark SQL DDL – Views]({{< ref "spark/sql-ddl#view" >}})
- [REST Catalog Overview]({{< ref "concepts/rest/overview" >}})
- [REST Catalog View API]({{< ref "concepts/rest/rest-api" >}})