ALTER TABLE DEDUP ENABLE
Enable storage level data deduplication on inserts and configures UPSERT KEYS.
note
- Deduplication can only be enabled for Write-Ahead Log (WAL) tables.
- Enabling deduplication does not have any effect on the existing data and only applies to newly inserted data. This means that a table with deduplication enabled can still contain duplicate data.
- Enabling deduplication does not have any effect on modifying data with
UPDATEstatements.
Syntax
ALTER TABLE tableName DEDUP ENABLE UPSERT KEYS(columnName [, columnName ...]);
UPSERT KEYS list can include one or more columns. The designated timestamp column must be
included in the UPSERT KEYS list.
Running ALTER TABLE DEDUP ENABLE on a table that already has deduplication
enabled is not an error.
In such cases, the UPSERT KEYS list overrides the previously set key column
list.
Example
To enable deduplication on the fx_trades table for the timestamp and
trade_id columns, where timestamp is the designated timestamp for the
table, use the following command:
ALTER TABLE fx_trades DEDUP ENABLE UPSERT KEYS(timestamp, trade_id);
See more example at data deduplication page