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Dec 16, 2022
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Docs: add example of spark extension for identifier fields #6444

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26 changes: 26 additions & 0 deletions docs/spark-ddl.md
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Expand Up @@ -446,3 +446,29 @@ ALTER TABLE prod.db.sample WRITE DISTRIBUTED BY PARTITION
```sql
ALTER TABLE prod.db.sample WRITE DISTRIBUTED BY PARTITION LOCALLY ORDERED BY category, id
```

### `ALTER TABLE ... SET IDENTIFIER FIELDS`

Iceberg supports setting identifier fields to a spec using `SET IDENTIFIER FIELDS`:

```sql
ALTER TABLE prod.db.sample SET IDENTIFIER FIELDS id
-- single column
ALTER TABLE prod.db.sample SET IDENTIFIER FIELDS id, data
-- multiple columns
```

identifier fields must be `NOT NULL`, The later `ALTER` statement will overwrite the previous setting.

### `ALTER TABLE ... DROP IDENTIFIER FIELDS`

Identifier fields can be removed using `DROP IDENTIFIER FIELDS`:

```sql
ALTER TABLE prod.db.sample DROP IDENTIFIER FIELDS id
-- single column
ALTER TABLE prod.db.sample DROP IDENTIFIER FIELDS id, data
-- multiple columns
```

Note that although the identifier is removed, the column will still exist in the table schema.