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ALTER TABLE SET TYPE

Converts a non-WAL table to WAL, or a WAL table to non-WAL.

info

Upgrading QuestDB?

Apply table conversions separately from the version upgrade.

If upgrading, match the following sequence:

  1. Convert/ALTER tables
  2. Restart
  3. Upgrade
  4. Restart

Syntax​

ALTER TABLE tableName SET TYPE [BYPASS] WAL;

Description​

The command schedules the conversion of the specified table to WAL or non-WAL type. The actual conversion takes place on the next restart of the server.

For a table that may hold merge-append partitions, first set cairo.o3.partition.merge.append.enabled=false, restart, and run ALTER TABLE trades SQUASH PARTITIONS; only then issue ALTER TABLE trades SET TYPE BYPASS WAL and restart again. Skipping these steps is unsupported.

If the command issued more than once before the restart, the last command overrides all previous ones.

If the target type of the conversion is the same as the current type of the table, the conversion request is ignored.

Examples​

To convert a non-WAL table to WAL:

ALTER TABLE weather SET TYPE WAL;
-- now restart instance

To convert a WAL table to non-WAL:

ALTER TABLE weather SET TYPE BYPASS WAL;
-- now restart instance