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Merge pull request #55860 from jrdi/filesystem-cache-docs

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Add load_metadata_threads to the documentation
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Raúl Marín 2023-10-20 14:59:47 +02:00 committed by GitHub
commit 07e3f10958
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4 changed files with 6 additions and 9 deletions
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1
docs/en/operations/server-configuration-parameters/settings.md
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@ -569,7 +569,6 @@ Both the cache for `local_disk`, and temporary data will be stored in `/tiny_loc
<max_size_rows>10M</max_size_rows>
<max_file_segment_size>1M</max_file_segment_size>
<cache_on_write_operations>1</cache_on_write_operations>
<do_not_evict_index_and_mark_files>0</do_not_evict_index_and_mark_files>
</tiny_local_cache>
<!-- highlight-end -->
</disks>

12
docs/en/operations/storing-data.md
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@ -114,7 +114,7 @@ Example of disk configuration:
## Using local cache {#using-local-cache}
It is possible to configure local cache over disks in storage configuration starting from version 22.3.
It is possible to configure local cache over disks in storage configuration starting from version 22.3.
For versions 22.3 - 22.7 cache is supported only for `s3` disk type. For versions >= 22.8 cache is supported for any disk type: S3, Azure, Local, Encrypted, etc.
For versions >= 23.5 cache is supported only for remote disk types: S3, Azure, HDFS.
Cache uses `LRU` cache policy.
@ -192,12 +192,12 @@ These settings should be defined in the disk configuration section.
- `enable_bypass_cache_with_threshold` - allows to skip cache completely in case the requested read range exceeds the threshold. Default: `false`. This threshold can be defined by `bypass_cache_threashold`. Default: `268435456` (`256Mi`).
- `do_not_evict_index_and_mark_files` - do not evict small frequently used files according to cache policy. Default: `false`. This setting was added in version 22.8. If you used filesystem cache before this version, then it will not work on versions starting from 22.8 if this setting is set to `true`. If you want to use this setting, clear old cache created before version 22.8 before upgrading.
- `max_file_segment_size` - a maximum size of a single cache file in bytes or in readable format (`ki, Mi, Gi, etc`, example `10Gi`). Default: `8388608` (`8Mi`).
- `max_elements` - a limit for a number of cache files. Default: `10000000`.
- `load_metadata_threads` - number of threads being used to load cache metadata on starting time. Default: `1`.
File Cache **query/profile settings**:
Some of these settings will disable cache features per query/profile that are enabled by default or in disk configuration settings. For example, you can enable cache in disk configuration and disable it per query/profile setting `enable_filesystem_cache` to `false`. Also setting `cache_on_write_operations` to `true` in disk configuration means that "write-though" cache is enabled. But if you need to disable this general setting per specific queries then setting `enable_filesystem_cache_on_write_operations` to `false` means that write operations cache will be disabled for a specific query/profile.
@ -248,9 +248,9 @@ DESCRIBE FILESYSTEM CACHE 's3_cache'
```
``` text
┌────max_size─┬─max_elements─┬─max_file_segment_size─┬─cache_on_write_operations─┬─enable_cache_hits_threshold─┬─current_size─┬─current_elements─┬─path────────┬─do_not_evict_index_and_mark_files─┐
│ 10000000000 │ 1048576 │ 104857600 │ 1 │ 0 │ 3276 │ 54 │ /s3_cache/ │ 1 │
└─────────────┴──────────────┴───────────────────────┴───────────────────────────┴─────────────────────────────┴──────────────┴──────────────────┴─────────────┴───────────────────────────────────┘
┌────max_size─┬─max_elements─┬─max_file_segment_size─┬─boundary_alignment─┬─cache_on_write_operations─┬─cache_hits_threshold─┬─current_size─┬─current_elements─┬─path───────┬─background_download_threads─┬─enable_bypass_cache_with_threshold─┐
│ 10000000000 │ 1048576 │ 104857600 │ 4194304 │ 1 │ 0 │ 3276 │ 54 │ /s3_cache/ │ 2 │ 0 │
└─────────────┴──────────────┴───────────────────────┴────────────────────┴───────────────────────────┴──────────────────────┴──────────────┴──────────────────┴────────────┴─────────────────────────────┴────────────────────────────────────┘
```
Cache current metrics:

1
tests/integration/test_merge_tree_s3/configs/config.d/storage_conf.xml
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@ -78,7 +78,6 @@
<disk>s3_r</disk>
<path>/s3_cache_r/</path>
<max_size>1000000000</max_size>
<do_not_evict_index_and_mark_files>1</do_not_evict_index_and_mark_files>
</s3_cache_r>
</disks>
<policies>

1
tests/integration/test_temporary_data_in_cache/configs/config.d/storage_configuration.xml
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@ -13,7 +13,6 @@
<max_size>10M</max_size>
<max_file_segment_size>1M</max_file_segment_size>
<cache_on_write_operations>1</cache_on_write_operations>
<do_not_evict_index_and_mark_files>0</do_not_evict_index_and_mark_files>
</tiny_local_cache>
<!-- Used to check free space in `/tiny_local_cache` using `system.disks` -->