> ## Documentation Index
> Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

> When performing queries, ClickHouse uses different caches.

# Cache types

When performing queries, ClickHouse uses different caches to speed up queries
and reduce the need to read from or write to disk.

The main cache types are:

* `mark_cache` — Cache of [marks](/docs/resources/develop-contribute/introduction/architecture#merge-tree) used by table engines of the [`MergeTree`](/docs/reference/engines/table-engines/mergetree-family/mergetree) family.
* `uncompressed_cache` — Cache of uncompressed data used by table engines of the [`MergeTree`](/docs/reference/engines/table-engines/mergetree-family/mergetree) family.
* Operating system page cache (used indirectly, for files with actual data).

There are also a host of additional cache types:

* DNS cache.
* [Regexp](/docs/reference/formats/Regexp) cache.
* Compiled expressions cache.
* [Vector similarity index](/docs/reference/engines/table-engines/mergetree-family/annindexes) cache.
* [Text index](/docs/reference/engines/table-engines/mergetree-family/textindexes#caching) cache.
* [Avro format](/docs/reference/formats/Avro/Avro) schemas cache.
* [Dictionaries](/docs/reference/statements/create/dictionary) data cache.
* Schema inference cache.
* [Filesystem cache](/docs/concepts/features/configuration/server-config/storing-data) over S3, Azure, Local and other disks.
* [Userspace page cache](/docs/concepts/features/performance/caches/userspace-page-cache)
* [Query cache](/docs/concepts/features/performance/caches/query-cache).
* [Query condition cache](/docs/concepts/features/performance/caches/query-condition-cache).
* Format schema cache.

Should you wish to clear one of the caches, for performance tuning, troubleshooting, or data consistency reasons,
you can use the [`SYSTEM CLEAR ... CACHE`](/docs/reference/statements/system) statement.