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> Documentation for Apply patches from lightweight updates

# Apply patches from lightweight updates

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        interaction: "click"
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};

```sql theme={null}
ALTER TABLE [db.]table [ON CLUSTER cluster] APPLY PATCHES [IN PARTITION partition_id]
```

The command manually triggers the physical materialization of patch parts created by [lightweight `UPDATE`](/reference/statements/update) statements. It forcefully applies pending patches to the data parts by rewriting only the affected columns.

<Note>
  * It only works for tables in the [`MergeTree`](/reference/engines/table-engines/mergetree-family/mergetree) family (including [replicated](/reference/engines/table-engines/mergetree-family/replication) tables).
  * This is a mutation operation and executes asynchronously in the background.
</Note>

<h2 id="when-to-use">
  When to use APPLY PATCHES
</h2>

<Tip>
  Generally, you should not need to use `APPLY PATCHES`
</Tip>

Patch parts are normally applied automatically during merges when the [`apply_patches_on_merge`](/reference/settings/merge-tree-settings#apply_patches_on_merge) setting is enabled (default). However, you may want to manually trigger patch application in these scenarios:

* To reduce the overhead of applying patches during `SELECT` queries
* To consolidate multiple patch parts before they accumulate
* To prepare data for backup or export with patches already materialized
* When `apply_patches_on_merge` is disabled and you want to control when patches are applied

<h2 id="examples">
  Examples
</h2>

Apply all pending patches for a table:

```sql theme={null}
ALTER TABLE my_table APPLY PATCHES;
```

Apply patches only for a specific partition:

```sql theme={null}
ALTER TABLE my_table APPLY PATCHES IN PARTITION '2024-01';
```

Combine with other operations:

```sql theme={null}
ALTER TABLE my_table APPLY PATCHES, UPDATE column = value WHERE condition;
```

<h2 id="monitor">
  Monitoring patch application
</h2>

You can monitor the progress of patch application using the [`system.mutations`](/reference/system-tables/mutations) table:

```sql theme={null}
SELECT * FROM system.mutations
WHERE table = 'my_table' AND command LIKE '%APPLY PATCHES%';
```

<h2 id="see-also">
  See also
</h2>

* [Lightweight `UPDATE`](/reference/statements/update) - Create patch parts with lightweight updates
* [`apply_patches_on_merge` setting](/reference/settings/merge-tree-settings#apply_patches_on_merge) - Control automatic patch application during merges