> ## Documentation Index
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> Use this file to discover all available pages before exploring further.

> System table containing information about merges and part mutations currently in process for tables in the MergeTree family.

# system.merges

<Info>
  **Querying in ClickHouse Cloud**

  The data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the `clusterAllReplicas` function. See [here](/reference/system-tables/overview#system-tables-in-clickhouse-cloud) for further details.
</Info>

<h2 id="description">
  Description
</h2>

Contains information about merges and part mutations currently in process for tables in the MergeTree family.

<h2 id="columns">
  Columns
</h2>

* `database` ([String](/reference/data-types)) — The name of the database the table is in.
* `table` ([String](/reference/data-types)) — Table name.
* `elapsed` ([Float64](/reference/data-types)) — The time elapsed (in seconds) since the merge started.
* `progress` ([Float64](/reference/data-types)) — The percentage of completed work from 0 to 1.
* `num_parts` ([UInt64](/reference/data-types)) — The number of parts to be merged.
* `source_part_names` ([Array(String)](/reference/data-types)) — The list of source parts names.
* `result_part_name` ([String](/reference/data-types)) — The name of the part that will be formed as the result of merging.
* `source_part_paths` ([Array(String)](/reference/data-types)) — The list of paths for each source part.
* `result_part_path` ([String](/reference/data-types)) — The path of the part that will be formed as the result of merging.
* `partition_id` ([String](/reference/data-types)) — The identifier of the partition where the merge is happening.
* `partition` ([String](/reference/data-types)) — The name of the partition
* `is_mutation` ([UInt8](/reference/data-types)) — 1 if this process is a part mutation.
* `total_size_bytes_compressed` ([UInt64](/reference/data-types)) — The total size of the compressed data in the merged chunks.
* `total_size_bytes_uncompressed` ([UInt64](/reference/data-types)) — The total size of compressed data in the merged chunks.
* `total_size_marks` ([UInt64](/reference/data-types)) — The total number of marks in the merged parts.
* `bytes_read_uncompressed` ([UInt64](/reference/data-types)) — Number of bytes read, uncompressed.
* `rows_read` ([UInt64](/reference/data-types)) — Number of rows read.
* `bytes_written_uncompressed` ([UInt64](/reference/data-types)) — Number of bytes written, uncompressed.
* `rows_written` ([UInt64](/reference/data-types)) — Number of rows written.
* `columns_written` ([UInt64](/reference/data-types)) — Number of columns written (for Vertical merge algorithm).
* `memory_usage` ([UInt64](/reference/data-types)) — Memory consumption of the merge process.
* `thread_id` ([UInt64](/reference/data-types)) — Thread ID of the merge process.
* `merge_type` ([String](/reference/data-types)) — The type of current merge. Empty if it's an mutation.
* `merge_algorithm` ([String](/reference/data-types)) — The algorithm used in current merge. Empty if it's an mutation.