# system.part_log {#system_tables-part-log}

The `system.part_log` table is created only if the [part_log](../../operations/server-configuration-parameters/settings.md#server_configuration_parameters-part-log) server setting is specified.

This table contains information about events that occurred with [data parts](../../engines/table-engines/mergetree-family/custom-partitioning-key.md) in the [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) family tables, such as adding or merging data.

The `system.part_log` table contains the following columns:

-   `event_type` (Enum) — Type of the event that occurred with the data part. Can have one of the following values:
    -   `NEW_PART` — Inserting of a new data part.
    -   `MERGE_PARTS` — Merging of data parts.
    -   `DOWNLOAD_PART` — Downloading a data part.
    -   `REMOVE_PART` — Removing or detaching a data part using [DETACH PARTITION](../../sql-reference/statements/alter/partition.md#alter_detach-partition).
    -   `MUTATE_PART` — Mutating of a data part.
    -   `MOVE_PART` — Moving the data part from the one disk to another one.
-   `event_date` (Date) — Event date.
-   `event_time` (DateTime) — Event time.
-   `duration_ms` (UInt64) — Duration.
-   `database` (String) — Name of the database the data part is in.
-   `table` (String) — Name of the table the data part is in.
-   `part_name` (String) — Name of the data part.
-   `partition_id` (String) — ID of the partition that the data part was inserted to. The column takes the ‘all’ value if the partitioning is by `tuple()`.
-   `rows` (UInt64) — The number of rows in the data part.
-   `size_in_bytes` (UInt64) — Size of the data part in bytes.
-   `merged_from` (Array(String)) — An array of names of the parts which the current part was made up from (after the merge).
-   `bytes_uncompressed` (UInt64) — Size of uncompressed bytes.
-   `read_rows` (UInt64) — The number of rows was read during the merge.
-   `read_bytes` (UInt64) — The number of bytes was read during the merge.
-   `error` (UInt16) — The code number of the occurred error.
-   `exception` (String) — Text message of the occurred error.

The `system.part_log` table is created after the first inserting data to the `MergeTree` table.

[Original article](https://clickhouse.tech/docs/en/operations/system_tables/part_log) <!--hide-->