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87 lines
2.5 KiB
Markdown
87 lines
2.5 KiB
Markdown
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<a name="table_engines-graphitemergetree"></a>
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# 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.
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Graphite stores full data in ClickHouse, and data can be retrieved in the following ways:
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- Without thinning.
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Using the [MergeTree](mergetree.md#table_engines-mergetree) engine.
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- With thinning.
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Using the `GraphiteMergeTree` engine.
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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.
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## Using the engine
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The Graphite data table must contain the following fields at minimum:
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- `Path` – The metric name (Graphite sensor).
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- `Time` – The time for measuring the metric.
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- `Value` – The value of the metric at the time set in Time.
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- `Version` – Determines which value of the metric with the same Path and Time will remain in the database.
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Rollup pattern:
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```text
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pattern
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regexp
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function
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age -> precision
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...
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pattern
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...
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default
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function
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age -> precision
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...
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```
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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.
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Fields in the pattern.
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- `age` – The minimum age of the data in seconds.
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- `function` – The name of the aggregating function to apply to data whose age falls within the range `[age, age + precision]`.
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- `precision`– How precisely to define the age of the data in seconds.
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- `regexp`– A pattern for the metric name.
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Example of settings:
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```xml
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<graphite_rollup>
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<pattern>
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<regexp>click_cost</regexp>
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<function>any</function>
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<retention>
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<age>0</age>
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<precision>5</precision>
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</retention>
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<retention>
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<age>86400</age>
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<precision>60</precision>
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</retention>
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</pattern>
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<default>
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<function>max</function>
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<retention>
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<age>0</age>
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<precision>60</precision>
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</retention>
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<retention>
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<age>3600</age>
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<precision>300</precision>
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</retention>
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<retention>
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<age>86400</age>
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<precision>3600</precision>
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</retention>
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</default>
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</graphite_rollup>
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```
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