ClickHouse/docs/en/table_engines/graphitemergetree.md

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<a name="table_engines-graphitemergetree"></a>
# GraphiteMergeTree
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This engine is designed for rollup (thinning and aggregating/averaging) [Graphite](http://graphite.readthedocs.io/en/latest/index.html) data. It may be helpful to developers who want to use ClickHouse as a data store for Graphite.
Graphite stores full data in ClickHouse, and data can be retrieved in the following ways:
- Without thinning.
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Uses the [MergeTree](mergetree.md#table_engines-mergetree) engine.
- With thinning.
Using the `GraphiteMergeTree` engine.
The engine inherits properties from MergeTree. The settings for thinning data are defined by the [graphite_rollup](../operations/server_settings/settings.md#server_settings-graphite_rollup) parameter in the server configuration.
## Using the engine
The Graphite data table must contain the following fields at minimum:
- `Path` The metric name (Graphite sensor).
- `Time` The time for measuring the metric.
- `Value` The value of the metric at the time set in Time.
- `Version` Determines which value of the metric with the same Path and Time will remain in the database.
Rollup pattern:
```text
pattern
regexp
function
age -> precision
...
pattern
...
default
function
age -> precision
...
```
When processing a record, ClickHouse will check the rules in the `pattern`clause. If the metric name matches the `regexp`, the rules from `pattern` are applied; otherwise, the rules from `default` are used.
Fields in the pattern.
- `age` The minimum age of the data in seconds.
- `function` The name of the aggregating function to apply to data whose age falls within the range `[age, age + precision]`.
- `precision` How precisely to define the age of the data in seconds.
- `regexp` A pattern for the metric name.
Example of settings:
```xml
<graphite_rollup>
<pattern>
<regexp>click_cost</regexp>
<function>any</function>
<retention>
<age>0</age>
<precision>5</precision>
</retention>
<retention>
<age>86400</age>
<precision>60</precision>
</retention>
</pattern>
<default>
<function>max</function>
<retention>
<age>0</age>
<precision>60</precision>
</retention>
<retention>
<age>3600</age>
<precision>300</precision>
</retention>
<retention>
<age>86400</age>
<precision>3600</precision>
</retention>
</default>
</graphite_rollup>
```
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