88 lines
4.0 KiB
Markdown
88 lines
4.0 KiB
Markdown
---
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title: Design your schema
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description: >
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Use schema design guidelines to improve write and query performance in your
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InfluxDB cluster.
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menu:
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influxdb_clustered:
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name: Design your schema
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parent: Optimize your cluster
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weight: 201
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related:
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- /influxdb/clustered/write-data/best-practices/schema-design/
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---
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Schema design can have a significant impact on both write and query performance
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in your InfluxDB cluster. The items below cover high-level considerations and
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recommendation. For detailed recommendations, see
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[Schema design recommendations](/influxdb/clustered/write-data/best-practices/schema-design/).
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## Understand the difference between tags and fields
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In the [InfluxDB data structure](/influxdb/clustered/write-data/best-practices/schema-design/#influxdb-data-structure),
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there are three main "categories" of information--timestamps, tags, and fields.
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Understanding the difference between what should be a tag and what should be a
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field is important when designing your schema.
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Use the following guidelines to determine what should be tags versus fields:
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- Use tags to store metadata that provides information about the source or
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context of the data.
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- Use fields to store measured values.
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- Field values typically change over time. Tag values do not.
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- Tag values can only be strings.
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- Field values can be any of the following data types:
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- Integer
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- Unsigned integer
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- Float
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- String
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- Boolean
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For more information, see [Tags versus fields](/influxdb/clustered/write-data/best-practices/schema-design/#tags-versus-fields).
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## Schema restrictions
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InfluxDB enforces the following schema restrictions:
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- You cannot use the same name for a tag and a field in the same table.
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- There is a limit to the number of columns you can store in a table.
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By default, tables can have up to 250 columns.
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For more information, see [InfluxDB schema restrictions](/influxdb/clustered/write-data/best-practices/schema-design/#schema-restrictions).
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## Design for performance
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The following guidelines help to ensure write and query performance:
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{{% caption %}}
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Follow the links below for more detailed information.
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{{% /caption %}}
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- [Avoid wide schemas](/influxdb/clustered/write-data/best-practices/schema-design/#avoid-wide-schemas):
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A wide schema is one with a large number of columns (tags and fields).
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- [Avoid sparse schemas](/influxdb/clustered/write-data/best-practices/schema-design/#avoid-sparse-schemas):
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A sparse schema is one where, for many rows, columns contain null values.
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- [Keep table schemas homogenous](/influxdb/clustered/write-data/best-practices/schema-design/#table-schemas-should-be-homogenous):
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A homogenous table schema is one where every row has values for all tags and fields.
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- [Use the best data type for your data](/influxdb/clustered/write-data/best-practices/schema-design/#use-the-best-data-type-for-your-data):
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Write integers as integers, decimals as floats, and booleans as booleans.
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Queries against a field that stores integers outperforms a query against string data.
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## Design for query simplicity
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The following guidelines help to ensure that, when querying data, the schema
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makes it easy to write queries:
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{{% caption %}}
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Follow the links below for more detailed information.
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{{% /caption %}}
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- [Keep table names, tags, and fields simple](/influxdb/clustered/write-data/best-practices/schema-design/#keep-table-names-tags-and-fields-simple):
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Use one tag or one field for each data attribute.
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If your source data contains multiple data attributes in a single parameter,
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split each attribute into its own tag or field.
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- [Avoid keywords and special characters](/influxdb/clustered/write-data/best-practices/schema-design/#avoid-keywords-and-special-characters):
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Reserved keywords or special characters in table names, tag keys, and field
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keys makes writing queries more complex.
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{{< page-nav prev="/influxdb/clustered/install/optimize-cluster/" prevText="Optimize your cluster" next="/influxdb/clustered/install/optimize-cluster/write-methods/" nextText="Identify write methods" >}} |