136 lines
5.8 KiB
Markdown
136 lines
5.8 KiB
Markdown
The underlying query engine for the InfluxDB SQL implementation,
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[DataFusion](https://arrow.apache.org/datafusion/index.html), provides commands
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that return metadata related to your data schema.
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To access this information, use the `SHOW TABLES`, `SHOW COLUMNS`, and
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`SHOW ALL` commands or query views in the [ISO](https://www.iso.org/) SQL
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`information_schema` schema.
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In the context of InfluxDB, a [measurement](/influxdb/version/reference/glossary/#measurement)
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is represented as a table. Time, [tags](/influxdb/version/reference/glossary/#tag),
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and [fields](/influxdb/version/reference/glossary/#field) are each represented
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by columns in a table.
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- [SHOW TABLES](#show-tables)
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- [Example SHOW TABLES output](#example-show-tables-output)
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- [SHOW COLUMNS](#show-columns)
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- [Example SHOW COLUMNS output](#example-show-columns-output)
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- [SHOW ALL](#show-all)
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- [Example SHOW ALL output](#view-show-all-example-output)
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## SHOW TABLES
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Returns information about tables (measurements) in an InfluxDB bucket.
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```sql
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SHOW TABLES
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```
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You can also query the `information_schema.tables` view:
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```sql
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SELECT * FROM information_schema.tables
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```
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#### Example SHOW TABLES output
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_Measurements are those that use the **`iox` table schema**._
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| table_catalog | table_schema | table_name | table_type |
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| :------------ | :----------------- | :---------- | :--------- |
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| public | iox | home | BASE TABLE |
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| public | system | queries | BASE TABLE |
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| public | information_schema | tables | VIEW |
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| public | information_schema | views | VIEW |
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| public | information_schema | columns | VIEW |
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| public | information_schema | df_settings | VIEW |
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## SHOW COLUMNS
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Returns information about the schema of a table (measurement) in an InfluxDB bucket.
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```sql
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SHOW COLUMNS FROM example_table
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```
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You can also query the `information_schema.columns` view:
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```sql
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SELECT
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table_catalog,
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table_schema,
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table_name,
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column_name,
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data_type,
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is_nullable
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FROM information_schema.columns
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WHERE table_name = 'example_table'
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```
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#### Example SHOW COLUMNS output
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| table_catalog | table_schema | table_name | column_name | data_type | is_nullable |
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| :------------ | :----------- | :--------- | :---------- | :-------------------------- | :---------- |
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| public | iox | home | co | Int64 | YES |
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| public | iox | home | hum | Float64 | YES |
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| public | iox | home | room | Dictionary(Int32, Utf8) | YES |
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| public | iox | home | temp | Float64 | YES |
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| public | iox | home | time | Timestamp(Nanosecond, None) | NO |
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## SHOW ALL
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Returns the configuration options of the current session.
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```sql
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SHOW ALL
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```
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You can also query the `information_schema.df_settings` view:
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```sql
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SELECT * FROM information_schema.df_settings
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```
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{{< expand-wrapper >}}
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{{% expand "View `SHOW ALL` example output" %}}
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| name | setting |
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| :-------------------------------------------------------- | :------- |
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| datafusion.catalog.create_default_catalog_and_schema | true |
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| datafusion.catalog.default_catalog | public |
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| datafusion.catalog.default_schema | iox |
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| datafusion.catalog.format | |
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| datafusion.catalog.has_header | false |
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| datafusion.catalog.information_schema | true |
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| datafusion.catalog.location | |
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| datafusion.execution.batch_size | 8192 |
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| datafusion.execution.coalesce_batches | true |
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| datafusion.execution.collect_statistics | false |
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| datafusion.execution.parquet.enable_page_index | false |
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| datafusion.execution.parquet.metadata_size_hint | |
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| datafusion.execution.parquet.pruning | true |
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| datafusion.execution.parquet.pushdown_filters | true |
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| datafusion.execution.parquet.reorder_filters | true |
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| datafusion.execution.parquet.skip_metadata | true |
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| datafusion.execution.target_partitions | 4 |
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| datafusion.execution.time_zone | +00:00 |
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| datafusion.explain.logical_plan_only | false |
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| datafusion.explain.physical_plan_only | false |
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| datafusion.optimizer.enable_round_robin_repartition | true |
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| datafusion.optimizer.filter_null_join_keys | false |
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| datafusion.optimizer.hash_join_single_partition_threshold | 1048576 |
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| datafusion.optimizer.max_passes | 3 |
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| datafusion.optimizer.prefer_hash_join | true |
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| datafusion.optimizer.repartition_aggregations | true |
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| datafusion.optimizer.repartition_file_min_size | 10485760 |
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| datafusion.optimizer.repartition_file_scans | true |
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| datafusion.optimizer.repartition_joins | true |
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| datafusion.optimizer.repartition_sorts | false |
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| datafusion.optimizer.repartition_windows | true |
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| datafusion.optimizer.skip_failed_rules | true |
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| datafusion.optimizer.top_down_join_key_reordering | true |
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| datafusion.sql_parser.enable_ident_normalization | true |
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| datafusion.sql_parser.parse_float_as_decimal | false |
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{{% /expand %}}
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{{< /expand-wrapper >}}
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