RussellSpitzer commented on a change in pull request #2067:
URL: https://github.com/apache/iceberg/pull/2067#discussion_r557642990
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File path: site/docs/spark.md
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@@ -814,3 +815,320 @@ This type conversion table describes how Iceberg types
are converted to the Spar
| struct | struct | |
| list | array | |
| map | map | |
+
+## Procedures
+
+In Spark 3 Iceberg provides an SQL API for accomplishing the [maintenance
actions](maintenance.md). Support for
+stored procedures is tied to the DataSourceV2 catalog and requires that the
Iceberg Extensions are enabled for the
+Spark Session.
+
+### General Usage
+
+To call an Iceberg stored procedure, execute a `CALL` command against the
iceberg catalog. All procedures are added to
+the `system` keyspace. Procedures can take positional or named arguments.
+
+#### Generic Call with Positional Arguments
+```sql
+ CALL catalog_name.system.procedure_name(arg_1, arg_2, ... arg_n)
+```
+
+#### Generic Call with Named Arguments
+```sql
+ CALL catalog_name.system.procedure_name(arg_name_2 => arg_2, arg_name_1 =>
arg_1)
+```
+
+### Cherrypick Snapshot Procedure
+
+A procedure that applies changes in a given snapshot and creates a new
snapshot which will
+be set as the current snapshot in a table.
+
+**Note** this procedure invalidates all cached Spark plans that reference the
affected table
+
+#### Usage
+
+| Argument Name | Required? | Type | Description |
+|---------------|-----------|------|-------------|
+| table | ✔️ | String | Name of table to perform cherrypick on |
+| snapshot_id | ✔️ | Long | The snapshot ID to cherrypick |
+
+#### Output
+
+| Output Name | Type | Description |
+| ------------|------|-------------|
+| source_snapshot_id | Long | The snapshot before applying the cherrypick |
+| current_snapshot_id | Long | The current snapshot now that the cherrypick
has been applied|
+
+#### Examples
+
+Cherrypick Snapshot 1
+```sql
+ CALL catalog_name hive_prod.system.cherrypick_snapshot('my_table', 1)
+```
+
+Cherrypick Snapshot 1 with named args
+```sql
+ CALL catalog_name hive_prod.system.cherrypick_snapshot(snapshot_id => 1,
table => 'my_table' )
+```
+
+### Expire Snapshot Procedure
+
+Each write/update/delete/upsert/compaction in Iceberg produces a new snapshot
while keeping the old data and metadata
+around for snapshot isolation and time travel. The `expire_snapshots`
procedure can be used to remove older snapshots
+and their files which are no longer needed.
+
+This procedure will remove old snapshots and data files which are uniquely
required by those old snapshots. This means
+the ``expire_snapshots`` procedure will never remove files which are still
required by a non-expired snapshot.
+
+#### Usage
+
+| Argument Name | Required? | Type | Description |
+|---------------|-----------|------|-------------|
+| table | ✔️ | String | Name of table to expire snapshots from |
+| older_than | ️ | Timestamp | Remove snapshots older than this date
(Defaults to 5 days ago) |
+| retain_last | | Int | Length of history to preserve regardless of
older_than target (Defaults to 1)|
+
+#### Output
+
+| Output Name | Type | Description |
+| ------------|------|-------------|
+| deleted_data_files_count | Long | Data files deleted by this operation |
+| deleted_manifest_files_count | Long | Manifest files deleted by this
operation |
+| deleted_manifest_lists_count | Long | Manifest List files deleted by this
operation |
+
+#### Examples
+
+Remove snapshots older than 10 days ago, but retain the last 100 Snapshots.
+```sql
+ CALL hive_prod.system.expire_snapshots('db.sample',
date_sub(current_date(), 10), 100)
+```
+
+Erase all snapshots older than the current timestamp but retains the last 5
snapshots made.
+```sql
+ CALL hive_prod.system.expire_snapshots(table => 'db.sample', retain_last
=> 5)
+```
+
+### Migrate Table Procedure
+
+Converts a table known to Spark in this catalog into a Iceberg table. This is
manily for taking
+hive tables and fully converting them into Iceberg tables. The
[snapshot](#snapshot-table-procedure) procedure
+can be used for making Iceberg tables without effecting the underlying table.
The migrated table will preserve all
Review comment:
It's hard to word this. It is basically like "Create Table As SELECT"
but you don't do a select, it uses the original files. So we make a new Iceberg
table, but it refers to the files that were in this other source table at the
time.
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