Iceberg Spark Procedures for Snapshot and Metadata

Spark Procedures

Usage

Procedures can be used from any configured Iceberg catalog with CALL. All procedures are in the namespace system.

CALL supports passing arguments by name (recommended) or by position. Mixing position and named arguments is not supported.

Named arguments

All procedure arguments are named. When passing arguments by name, arguments can be in any order and any optional argument can be omitted.

CALL catalog_name.system.procedure_name(arg_name_2 => arg_2, arg_name_1 => arg_1)

Positional arguments

When passing arguments by position, only the ending arguments may be omitted if they are optional.

CALL catalog_name.system.procedure_name(arg_1, arg_2, ... arg_n)

Snapshot management

rollback_to_snapshot

Roll back a table to a specific snapshot ID.

To roll back to a specific time, use rollback_to_timestamp.

info

This procedure invalidates all cached Spark plans that reference the affected table.

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to update
snapshot_id	✔️	long	Snapshot ID to rollback to

Output

Output Name	Type	Description
previous_snapshot_id	long	The current snapshot ID before the rollback
current_snapshot_id	long	The new current snapshot ID

Example

Roll back table db.sample to snapshot ID 1:

CALL catalog_name.system.rollback_to_snapshot('db.sample', 1)

rollback_to_timestamp

Roll back a table to the snapshot that was current at some time.

info

This procedure invalidates all cached Spark plans that reference the affected table.

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to update
timestamp	✔️	timestamp	A timestamp to rollback to

Output

Output Name	Type	Description
previous_snapshot_id	long	The current snapshot ID before the rollback
current_snapshot_id	long	The new current snapshot ID

Example

Roll back db.sample to a specific day and time.

CALL catalog_name.system.rollback_to_timestamp('db.sample', TIMESTAMP '2021-06-30 00:00:00.000')

set_current_snapshot

Sets the current snapshot ID for a table.

Unlike rollback, the snapshot is not required to be an ancestor of the current table state.

info

This procedure invalidates all cached Spark plans that reference the affected table.

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to update
snapshot_id	✔️	long	Snapshot ID to set as current

Output

Output Name	Type	Description
previous_snapshot_id	long	The current snapshot ID before the rollback
current_snapshot_id	long	The new current snapshot ID

Example

Set the current snapshot for db.sample to 1:

CALL catalog_name.system.set_current_snapshot('db.sample', 1)

cherrypick_snapshot

Cherry-picks changes from a snapshot into the current table state.

Cherry-picking creates a new snapshot from an existing snapshot without altering or removing the original.

Only append and dynamic overwrite snapshots can be cherry-picked.

info

This procedure invalidates all cached Spark plans that reference the affected table.

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to update
snapshot_id	✔️	long	The snapshot ID to cherry-pick

Output

Output Name	Type	Description
source_snapshot_id	long	The table's current snapshot before the cherry-pick
current_snapshot_id	long	The snapshot ID created by applying the cherry-pick

Examples

Cherry-pick snapshot 1

CALL catalog_name.system.cherrypick_snapshot('my_table', 1)

Cherry-pick snapshot 1 with named args

CALL catalog_name.system.cherrypick_snapshot(snapshot_id => 1, table => 'my_table' )

Metadata management

Many maintenance actions can be performed using Iceberg stored procedures. Data Compaction Job

expire_snapshots

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 the table to update
older_than		timestamp	Timestamp before which snapshots will be removed (Default: 5 days ago)
retain_last		int	Number of ancestor snapshots to preserve regardless of older_than (defaults to 1)
max_concurrent_deletes		int	Size of the thread pool used for delete file actions (by default, no thread pool is used)
stream_results		boolean	When true, deletion files will be sent to Spark driver by RDD partition (by default, all the files will be sent to Spark driver). This option is recommended to set to true to prevent Spark driver OOM from large file size

If older_than and retain_last are omitted, the table's expiration properties will be used.

Output

Output Name	Type	Description
deleted_data_files_count	long	Number of data files deleted by this operation
deleted_manifest_files_count	long	Number of manifest files deleted by this operation
deleted_manifest_lists_count	long	Number of manifest List files deleted by this operation

Examples

Remove snapshots older than specific day and time, but retain the last 100 snapshots:

CALL hive_prod.system.expire_snapshots('db.sample', TIMESTAMP '2021-06-30 00:00:00.000', 100)

remove_orphan_files

Used to remove files which are not referenced in any metadata files of an Iceberg table and can thus be considered "orphaned".

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to clean
older_than		timestamp	Remove orphan files created before this timestamp (Defaults to 3 days ago)
location		string	Directory to look for files in (defaults to the table's location)
dry_run		boolean	When true, don't actually remove files (defaults to false)
max_concurrent_deletes		int	Size of the thread pool used for delete file actions (by default, no thread pool is used)

Output

Output Name	Type	Description
orphan_file_location	String	The path to each file determined to be an orphan by this command

Examples

List all the files that are candidates for removal by performing a dry run of the remove_orphan_files command on this table without actually removing them:

CALL catalog_name.system.remove_orphan_files(table => 'db.sample', dry_run => true)

Remove any files in the tablelocation/data folder which are not known to the table db.sample.

CALL catalog_name.system.remove_orphan_files(table => 'db.sample', location => 'tablelocation/data')

rewrite_data_files

Iceberg tracks each data file in a table. More data files leads to more metadata stored in manifest files, and small data files causes an unnecessary amount of metadata and less efficient queries from file open costs.

Iceberg can compact data files in parallel using Spark with the rewriteDataFiles action. This will combine small files into larger files to reduce metadata overhead and runtime file open cost.

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to update
strategy		string	Name of the strategy - binpack or sort. Defaults to binpack strategy
sort_order		string	Comma separated sort_order_column. Where sort_order_column is a space separated sort order info per column (ColumnName SortDirection NullOrder). SortDirection can be ASC or DESC. NullOrder can be NULLS FIRST or NULLS LAST
options		map<string, string>	Options to be used for actions
where		string	predicate as a string used for filtering the files. Note that all files that may contain data matching the filter will be selected for rewriting

Output

Output Name	Type	Description
rewritten_data_files_count	int	Number of data which were re-written by this command
added_data_files_count	int	Number of new data files which were written by this command

Examples

Rewrite the data files in table db.sample using the default rewrite algorithm of bin-packing to combine small files
and also split large files according to the default write size of the table.

CALL catalog_name.system.rewrite_data_files('db.sample')

Rewrite the data files in table db.sample by sorting all the data on id and name
using the same defaults as bin-pack to determine which files to rewrite.

CALL catalog_name.system.rewrite_data_files(table => 'db.sample', strategy => 'sort', sort_order => 'id DESC NULLS LAST,name ASC NULLS FIRST')

Rewrite the data files in table db.sample using bin-pack strategy in any partition where more than 2 or more files need to be rewritten.

CALL catalog_name.system.rewrite_data_files(table => 'db.sample', options => map('min-input-files','2'))

Rewrite the data files in table db.sample and select the files that may contain data matching the filter (id = 3 and name = "foo") to be rewritten.

CALL catalog_name.system.rewrite_data_files(table => 'db.sample', where => 'id = 3 and name = "foo"')

rewrite_manifests

Rewrite manifests for a table to optimize scan planning.

Data files in manifests are sorted by fields in the partition spec. This procedure runs in parallel using a Spark job.

info

This procedure invalidates all cached Spark plans that reference the affected table.

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to update
use_caching		boolean	Use Spark caching during operation (defaults to true)

Output

Output Name	Type	Description
rewritten_manifests_count	int	Number of manifests which were re-written by this command
added_mainfests_count	int	Number of new manifest files which were written by this command

Examples

Rewrite the manifests in table db.sample and align manifest files with table partitioning.

CALL catalog_name.system.rewrite_manifests('db.sample')

Rewrite the manifests in table db.sample and disable the use of Spark caching. This could be done to avoid memory issues on executors.

CALL catalog_name.system.rewrite_manifests('db.sample', false)

Table migration

The snapshot and migrate procedures help test and migrate existing Hive or Spark tables to Iceberg.

snapshot

Create a light-weight temporary copy of a table for testing, without changing the source table.

The newly created table can be changed or written to without affecting the source table, but the snapshot uses the original table's data files.

When inserts or overwrites run on the snapshot, new files are placed in the snapshot table's location rather than the original table location.

When finished testing a snapshot table, clean it up by running DROP TABLE.

info

Because tables created by snapshot are not the sole owners of their data files, they are prohibited from
actions like expire_snapshots which would physically delete data files. Iceberg deletes, which only effect metadata,
are still allowed. In addition, any operations which affect the original data files will disrupt the Snapshot's
integrity. DELETE statements executed against the original Hive table will remove original data files and the
snapshot table will no longer be able to access them.

See migrate to replace an existing table with an Iceberg table.

Usage

Argument Name	Required?	Type	Description
source_table	✔️	string	Name of the table to snapshot
table	✔️	string	Name of the new Iceberg table to create
location		string	Table location for the new table (delegated to the catalog by default)
properties	️	map<string, string>	Properties to add to the newly created table

Output

Output Name	Type	Description
imported_files_count	long	Number of files added to the new table

Examples

Make an isolated Iceberg table which references table db.sample named db.snap at the
catalog's default location for db.snap.

CALL catalog_name.system.snapshot('db.sample', 'db.snap')

Migrate an isolated Iceberg table which references table db.sample named db.snap at
a manually specified location /tmp/temptable/.

CALL catalog_name.system.snapshot('db.sample', 'db.snap', '/tmp/temptable/')

migrate

Replace a table with an Iceberg table, loaded with the source's data files.

Table schema, partitioning, properties, and location will be copied from the source table.

Migrate will fail if any table partition uses an unsupported format. Supported formats are Avro, Parquet, and ORC.
Existing data files are added to the Iceberg table's metadata and can be read using a name-to-id mapping created from the original table schema.

To leave the original table intact while testing, use snapshot to create new temporary table that shares source data files and schema.

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to migrate
properties	️	map<string, string>	Properties for the new Iceberg table

Output

Output Name	Type	Description
migrated_files_count	long	Number of files appended to the Iceberg table

Examples

Migrate the table db.sample in Spark's default catalog to an Iceberg table and add a property 'foo' set to 'bar':

CALL catalog_name.system.migrate('spark_catalog.db.sample', map('foo', 'bar'))

Migrate db.sample in the current catalog to an Iceberg table without adding any additional properties:

CALL catalog_name.system.migrate('db.sample')

add_files

Attempts to directly add files from a Hive or file based table into a given Iceberg table. Unlike migrate or
snapshot, add_files can import files from a specific partition or partitions and does not create a new Iceberg table.
This command will create metadata for the new files and will not move them. This procedure will not analyze the schema
of the files to determine if they actually match the schema of the Iceberg table. Upon completion, the Iceberg table
will then treat these files as if they are part of the set of files owned by Iceberg. This means any subsequent
expire_snapshot calls will be able to physically delete the added files. This method should not be used if
migrate or snapshot are possible.

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Table which will have files added to
source_table	✔️	string	Table where files should come from, paths are also possible in the form of `file_format`.`path`
partition_filter	️	map<string, string>	A map of partitions in the source table to import from

Warning : Schema is not validated, adding files with different schema to the Iceberg table will cause issues.

Warning : Files added by this method can be physically deleted by Iceberg operations

Examples

Add the files from table db.src_table, a Hive or Spark table registered in the session Catalog, to Iceberg table
db.tbl. Only add files that exist within partitions where part_col_1 is equal to A.

CALL spark_catalog.system.add_files(
table => 'db.tbl',
source_table => 'db.src_tbl',
partition_filter => map('part_col_1', 'A')
)

Add files from a parquet file based table at location path/to/table to the Iceberg table db.tbl. Add all
files regardless of what partition they belong to.

CALL spark_catalog.system.add_files(
  table => 'db.tbl',
  source_table => '`parquet`.`path/to/table`'
)

Metadata information

ancestors_of

Report the live snapshot IDs of parents of a specified snapshot

Usage

Argument Name	Required?	Type	Description
table	✔️	string	Name of the table to report live snapshot IDs
snapshot_id		long	Use a specified snapshot to get the live snapshot IDs of parents

tip : Using snapshot_id

Given snapshots history with roll back to B and addition of C' -> D'

A -> B - > C -> D
      \ -> C' -> (D')

Not specifying the snapshot ID would return A -> B -> C' -> D', while providing the snapshot ID of
D as an argument would return A-> B -> C -> D

Output

Output Name	Type	Description
snapshot_id	long	the ancestor snapshot id
timestamp	long	snapshot creation time

Examples

Get all the snapshot ancestors of current snapshots(default)

CALL spark_catalog.system.ancestors_of('db.tbl')

Get all the snapshot ancestors by a particular snapshot

CALL spark_catalog.system.ancestors_of('db.tbl', 1)
CALL spark_catalog.system.ancestors_of(snapshot_id => 1, table => 'db.tbl')