Truncating Tables

TRUNCATE TABLE removes all storage associated with the target table and its projections. Vertica preserves the table and the projection definitions. If the truncated table has out-of-date projections, those projections are cleared and marked up-to-date when TRUNCATE TABLE returns.

TRUNCATE TABLE commits the entire transaction after statement execution, even if truncating the table fails. You cannot roll back a TRUNCATE TABLE statement.

Use TRUNCATE TABLE for testing purposes. You can use it to remove all data from a table and load it with fresh data, without recreating the table and its projections.

Table Locking

TRUNCATE TABLE takes an O (owner) lock on the table until the truncation process completes. The savepoint is then released. If the operation cannot obtain an O lock on the target table, Vertica tries to close any internal Tuple Mover sessions that are running on that table. If successful, the operation can proceed. Explicit Tuple Mover operations that are running in user sessions do not close. If an explicit Tuple Mover operation is running on the table, the operation proceeds only when the operation is complete.

Restrictions

You cannot truncate an external table.

Examples

=> INSERT INTO sample_table (a) VALUES (3);
=> SELECT * FROM sample_table;
a
---
3
(1 row)

=> TRUNCATE TABLE sample_table;
TRUNCATE TABLE
=> SELECT * FROM sample_table;
a
---
(0 rows)