Branching feature

Branches are references to snapshots that have a lifecycle of their own. You can create a branch by basing the branch on a snapshot ID, a timestamp, or the state of your table. Using the SNAPSHOT RETENTION clause, you can create a branch that limits the number of snapshots of a table.

Iceberg branching is available in Hive only. Iceberg branches are not supported in Impala or Spark.

List snapshots and branches of a table

The following syntax lists timestamps and IDs of snapshots of an Iceberg table. You can use the list of snapshots to create branches and tags.

SELECT * FROM <database>.<table name>.HISTORY

The following syntax lists the branches and tags of a table.

SELECT * from <database>.<table name>.REFS

Create a branch

Use either system version or system time in the following syntax from Hive to create a branch. Tables must be Iceberg V2 tables.

ALTER TABLE <table name> CREATE BRANCH <branch name> FOR SYSTEM_VERSION AS OF <SNAPSHOT_ID>

ALTER TABLE <table name> CREATE BRANCH <branch name> FOR SYSTEM_TIME AS OF 'time_stamp' [expression]

If you do not have the ID or timestamp of a snapshot, you can also create a branch using the table name only and omitting the FOR clause

ALTER TABLE <table name> CREATE BRANCH <branch name>

This syntax creates a branch having the same state as the table.

Limit retained snapshots

When you create a branch, you can limit the number of snapshots a branch retains.

ALTER TABLE <table name> CREATE BRANCH <branch name> FOR SYSTEM_VERSION AS OF <timestamp> WITH SNAPSHOT RETENTION <integer limit> SNAPSHOTS;

Query a branch

From Hive, you can ingest data into an Iceberg branch using dot notation as you would a SQL table. The branch name prefix branch_ must be lowercase.

INSERT INTO TABLE <database name>.<table name>.branch_<branch name> VALUES (<column name>[, <column name> ...]

You can use SQL syntax to read, update, and delete data in a branch.

SELECT <column name 1>, <column name 2>, ... FROM <database name>.<table name>.branch_<branch name>

UPDATE TABLE <database name>.<table name>.branch_<branch name> SET <column name>=<new value>, <column name>=<new value> ... WHERE <condition>

DELETE FROM <database name>.<table name>.branch_<branch name> WHERE <condition>

Fast forward a branch

Fast forwarding a branch updates the state of one branch to another branch within its hierarchy. For example, you can fast-forward branch x to branch z as shown in the following example:

ALTER TABLE <table name> EXECUTE FAST-FORWARD 'x' 'z';

Branch x must be an ancestor of branch z. If you omit the second branch name, the named branch is fast-forwarded to the current branch.

Delete a branch

You can delete a branch related to a particular table, using the following syntax:

ALTER TABLE <table name> DROP BRANCH [IF EXISTS] <branch name>