ALTER TABLE RESUME WAL

Restarts transactions of a WAL table after recovery from errors.

Syntax​

Flow chart showing the syntax of the ALTER TABLE keyword Flow chart showing the syntax of ALTER TABLE with RESUME WAL keyword

Description​

sequencerTxn is the unique txn identification that the Sequencer issues to transactions.

When sequencerTxn is not specified, the operation resumes the WAL apply job from the next uncommitted transaction, including the failed one.

When sequencerTxn is not specified, the operation resumes the WAL apply job from the provided sequencerTxn number explicitly.

ALTER TABLE RESUME WAL is used to restart WAL table transactions after resolving errors. When transactions are stopped, the suspended status from the wal_tables() function is marked as true, and the sequencerTxn value indicates the last successful commit in the Sequencer. Once the error is resolved, ALTER TABLE RESUME WAL restarts the suspended WAL transactions from the failed transaction. Alternatively, an optional sequencerTxn value can be provided to skip the failed transaction.

Examples​

Using the wal_tables() function to investigate the table status:

List all tables
wal_tables();
namesuspendedwriterTxnsequencerTxn
sensor_walfalse66
weather_waltrue35

The table weather_wal is suspended. The last successful commit in the table is 3.

The following query restarts transactions from the failed transaction, 4:

ALTER TABLE  weather_wal RESUME WAL;

Alternatively, specifying the sequencerTxn to skip the failed commit (4 in this case):

ALTER TABLE  weather_wal RESUME WAL FROM TRANSACTION 5;

-- This is equivalent to

ALTER TABLE  weather_wal RESUME WAL FROM TXN 5;