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  - https://ydb.tech/docs/ru/yql/reference/syntax/alter_table/changefeed.md
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---
> **Documentation Index:** Fetch the complete configuration index at https://ydb.tech/docs/en/llms.txt

# Adding or removing a changefeed


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Supported only for [row-oriented](https://ydb.tech/docs/en/concepts/datamodel/table.md#row-oriented-tables) tables. Support for [column-oriented](https://ydb.tech/docs/en/concepts/datamodel/table.md#column-oriented-tables) tables is currently under development.
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`ADD CHANGEFEED <name> WITH (<option> = <value>[, ...])`: Adds a [changefeed](https://ydb.tech/docs/en/concepts/cdc.md) with the specified name and options.


## Changefeed options {#changefeed-options}

* `MODE`: Operation mode. Specifies what to write to a changefeed each time table data is altered.
   * `KEYS_ONLY`: Only the primary key components and change flag are written.
   * `UPDATES`: Updated column values that result from updates are written.
   * `NEW_IMAGE`: Any column values resulting from updates are written.
   * `OLD_IMAGE`: Any column values before updates are written.
   * `NEW_AND_OLD_IMAGES`: A combination of `NEW_IMAGE` and `OLD_IMAGE` modes. Any column values _prior to_ and _resulting from_ updates are written.
* `FORMAT`: Data write format.
   * `JSON`: Write data in [JSON](https://ydb.tech/docs/en/concepts/cdc.md#json-record-structure) format.
   * `DEBEZIUM_JSON`: Write data in the [Debezium-like JSON format](https://ydb.tech/docs/en/concepts/cdc.md#debezium-json-record-structure).
* `VIRTUAL_TIMESTAMPS`: Enabling/disabling [virtual timestamps](https://ydb.tech/docs/en/concepts/cdc.md#virtual-timestamps). Disabled by default.
* `BARRIERS_INTERVAL` — [barrier](https://ydb.tech/docs/en/concepts/cdc.md#barriers) emission interval. The value type is `Interval`. Disabled by default.
* `RETENTION_PERIOD`: [Record retention period](https://ydb.tech/docs/en/concepts/cdc.md#retention-period). The value type is `Interval` and the default value is 24 hours (`Interval('PT24H')`).
* `TOPIC_AUTO_PARTITIONING`: [Topic autopartitioning mode](https://ydb.tech/docs/en/concepts/cdc.md#topic-partitions):
    * `ENABLED` – An [autopartitioned topic](https://ydb.tech/docs/en/concepts/datamodel/topic.md#autopartitioning) will be created for this changefeed. The number of partitions in such a topic increases automatically as the table update rate increases. Topic autopartitioning parameters [can be configured](https://ydb.tech/docs/en/yql/reference/syntax/alter-topic.md#alter-topic).
    * `DISABLED` – A topic without [autopartitioning](https://ydb.tech/docs/en/concepts/datamodel/topic.md#autopartitioning) will be created for this changefeed. This is the default value.
* `TOPIC_MIN_ACTIVE_PARTITIONS`: [The initial number of topic partitions](https://ydb.tech/docs/en/concepts/cdc.md#topic-partitions). By default, the initial number of topic partitions is equal to the number of table partitions. For autopartitioned topics, the number of partitions increases automatically as the table update rate increases.
* `INITIAL_SCAN`: Enables/disables [initial table scan](https://ydb.tech/docs/en/concepts/cdc.md#initial-scan). Disabled by default.

The code below adds a changefeed named `updates_feed`, where the values of updated table columns will be exported in JSON format:

```yql
ALTER TABLE `series` ADD CHANGEFEED `updates_feed` WITH (
    FORMAT = 'JSON',
    MODE = 'UPDATES'
);
```

Records in this changefeed will be stored for 24 hours (default value). The code in the following example will create a changefeed with a record retention period of 12 hours:

```yql
ALTER TABLE `series` ADD CHANGEFEED `updates_feed` WITH (
    FORMAT = 'JSON',
    MODE = 'UPDATES',
    RETENTION_PERIOD = Interval('PT12H')
);
```

The example of creating a changefeed with enabled virtual timestamps:

```yql
ALTER TABLE `series` ADD CHANGEFEED `updates_feed` WITH (
    FORMAT = 'JSON',
    MODE = 'UPDATES',
    VIRTUAL_TIMESTAMPS = TRUE
);
```

The example of creating a changefeed with virtual timestamps and barriers every 10 seconds:

```yql
ALTER TABLE `series` ADD CHANGEFEED `updates_feed` WITH (
    FORMAT = 'JSON',
    MODE = 'UPDATES',
    VIRTUAL_TIMESTAMPS = TRUE,
    BARRIERS_INTERVAL = Interval('PT10S')
);
```

Example of creating a changefeed with initial scan:

```yql
ALTER TABLE `series` ADD CHANGEFEED `updates_feed` WITH (
    FORMAT = 'JSON',
    MODE = 'UPDATES',
    INITIAL_SCAN = TRUE
);
```

Example of creating a changefeed with autopartitioning:

```yql
ALTER TABLE `series` ADD CHANGEFEED `updates_feed` WITH (
    FORMAT = 'JSON',
    MODE = 'UPDATES',
    TOPIC_AUTO_PARTITIONING = 'ENABLED',
    TOPIC_MIN_ACTIVE_PARTITIONS = 2
);
```

`DROP CHANGEFEED`: Deletes the changefeed with the specified name. The code below deletes the `updates_feed` changefeed:

```yql
ALTER TABLE `series` DROP CHANGEFEED `updates_feed`;
```