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95 changes: 94 additions & 1 deletion docs/docs/spark-procedures.md
Original file line number Diff line number Diff line change
Expand Up @@ -972,4 +972,97 @@ CALL catalog_name.system.compute_table_stats(table => 'my_table', snapshot_id =>
Collect statistics of the snapshot with id `snap1` of table `my_table` for columns `col1` and `col2`
```sql
CALL catalog_name.system.compute_table_stats(table => 'my_table', snapshot_id => 'snap1', columns => array('col1', 'col2'));
```
```

## Table Replication

The `rewrite-table-path` procedure prepares an Iceberg table for copying to another location.

### `rewrite-table-path`

Stages a copy of the Iceberg table's metadata files where every absolute path source prefix is replaced by the specified target prefix.
This can be the starting point to fully or incrementally copy an Iceberg table to a new location.

!!! info
This procedure only stages rewritten metadata files and prepares a list of files to copy. The actual file copy is not included in this procedure.


| Argument Name | Required? | default | Type | Description |
|--------------------|-----------|------------------------------------------------|--------|------------------------------------------------------------------------|
| `table` | ✔️ | | string | Name of the table |
| `source_prefix` | ✔️ | | string | The existing prefix to be replaced |
| `target_prefix` | ✔️ | | string | The replacement prefix for `source_prefix` |
| `start_version` | | first metadata.json in table's metadata log | string | The name or path of the chronologically first metadata.json to rewrite |
| `end_version` | | latest metadata.json | string | The name or path of the chronologically last metadata.json to rewrite |
| `staging_location` | | new directory under table's metadata directory | string | The output location for newly modified metadata files |


#### Modes of operation

* Full Rewrite:
A full rewrite will rewrite all reachable metadata files
(this includes metadata.json, manifest lists, manifests, and position delete files), and will return all reachable files in the `file_list_location`. This is the default mode of operation for this procedure.

* Incremental Rewrite:
An incremental rewrite will only rewrite metadata files added between `start_version` and `end_version`, and will only return files added in this range in the `file_list_location`. Optional `start_version` and `end_version` can be provided to limit the scope of this procedure.


#### Output

| Output Name | Type | Description |
|----------------------|--------|-------------------------------------------------------------------|
| `latest_version` | string | Name of the latest metadata file rewritten by this procedure |
| `file_list_location` | string | Path to a CSV file containing a mapping of source to target paths |

##### File List
The file contains the copy plan for all files added to the table between `start_version` and `end_version`.

For each file, it specifies:

* Source Path: The original file path in the table, or the staging location if the file has been rewritten

* Target Path: The path with the replacement prefix

The following example shows a copy plan for three files:

```csv
sourcepath/datafile1.parquet,targetpath/datafile1.parquet
sourcepath/datafile2.parquet,targetpath/datafile2.parquet
stagingpath/manifest.avro,targetpath/manifest.avro
```

#### Examples

This example fully rewrites path of `my_table` from source location in HDFS to a target location in S3.
It will produce a new set of metadata in the default staging location under table's metadata directory.

```sql
CALL catalog_name.system.rewrite_table_path(
table => 'db.my_table',
source_prefix => "hdfs://nn:8020/path/to/source_table",
target_prefix => "s3a://bucket/prefix/db.db/my_table"
);
```

This example incrementally rewrites path of `my_table` between metadata versions `v2.metadata.json` and `v20.metadata.json`,
with new metadata files written to an explicit staging location.

```sql
CALL catalog_name.system.rewrite_table_path(
table => 'db.my_table',
source_prefix => "s3a://bucketOne/prefix/db.db/my_table",
target_prefix => "s3a://bucketTwo/prefix/db.db/my_table",
start_version => "v2.metadata.json",
end_version => "v20.metadata.json",
staging_location => "s3a://bucketStaging/my_table"
);
```

Once the rewrite completes, third-party tools (
eg. [Distcp](https://hadoop.apache.org/docs/current/hadoop-distcp/DistCp.html)) can copy the newly created
metadata files and data files to the target location.

Lastly, the [register_table](#register_table) procedure can be used to register the copied table in the target location with a catalog.

!!! warning
Iceberg tables with partition statistics files are not currently supported for path rewrite.