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Add SHOW CARDINALITY info to InfluxQL schema docs (#2941) 

Closes #2738
pull/2935/head^2
pierwill 2021-07-30 10:43:27 -05:00 committed by GitHub
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68
content/enterprise_influxdb/v1.9/query_language/explore-schema.md
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@ -1187,7 +1187,73 @@ Note that `SHOW FIELD KEYS` handles field type discrepancies differently from
For more information, see the
[How does InfluxDB handle field type discrepancies across shards?](/enterprise_influxdb/v1.9/troubleshooting/frequently-asked-questions/#how-does-influxdb-handle-field-type-discrepancies-across-shards).
### Filter meta queries by time
## `SHOW CARDINALITY`
`SHOW CARDINALITY` refers to the group of commands used to estimate or count exactly
the cardinality of measurements, series, tag keys, tag key values, and field keys.
For more information on the `SHOW CARDINALITY` commands,
see the [InfluxQL reference entry](/enterprise_influxdb/v1.9/query_language/spec/#show-cardinality).
### `SHOW FIELD KEY CARDINALITY`
```sql
-- show estimated cardinality of the field key set of current database
SHOW FIELD KEY CARDINALITY
-- show exact cardinality on field key set of specified database
SHOW FIELD KEY EXACT CARDINALITY ON mydb
```
### `SHOW MEASUREMENT KEY CARDINALITY`
```sql
-- show estimated cardinality of measurement set on current database
SHOW MEASUREMENT CARDINALITY
-- show exact cardinality of measurement set on specified database
SHOW MEASUREMENT EXACT CARDINALITY ON mydb
```
### `SHOW SERIES CARDINALITY`
```sql
-- show estimated cardinality of the series on current database
SHOW SERIES CARDINALITY
-- show estimated cardinality of the series on specified database
SHOW SERIES CARDINALITY ON mydb
-- show exact series cardinality
SHOW SERIES EXACT CARDINALITY
-- show series cardinality of the series on specified database
SHOW SERIES EXACT CARDINALITY ON mydb
```
### `SHOW TAG KEY CARDINALITY`
```sql
-- show estimated tag key cardinality
SHOW TAG KEY CARDINALITY
-- show exact tag key cardinality
SHOW TAG KEY EXACT CARDINALITY
```
### `SHOW TAG VALUES CARDINALITY`
```sql
-- show estimated tag key values cardinality for a specified tag key
SHOW TAG VALUES CARDINALITY WITH KEY = "myTagKey"
-- show estimated tag key values cardinality for a specified tag key
SHOW TAG VALUES CARDINALITY WITH KEY = "myTagKey"
-- show exact tag key values cardinality for a specified tag key
SHOW TAG VALUES EXACT CARDINALITY WITH KEY = "myTagKey"
-- show exact tag key values cardinality for a specified tag key
SHOW TAG VALUES EXACT CARDINALITY WITH KEY = "myTagKey"
```
## Filter meta queries by time
When you filter meta queries by time, you may see results outside of your specified time. Meta query results are filtered at the shard level, so results can be approximately as granular as your shard group duration. If your time filter spans multiple shards, you'll get results from all shards with points in the specified time range. To review your shards and timestamps on points in the shard, run `SHOW SHARDS`. To learn more about shards and their duration, see [recommended shard groups durations](/enterprise_influxdb/v1.9/concepts/schema_and_data_layout/#shard-group-duration-recommendations).

68
content/influxdb/v1.8/query_language/explore-schema.md
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@ -27,6 +27,7 @@ The following sections cover useful query syntax for exploring your [schema](/in
</tr>
<tr>
<td><a href="#show-field-keys">SHOW FIELD KEYS</a></td>
<td><a href="#show-cardinality">SHOW CARDINALITY</a></td>
<td><a href="#filter-meta-queries-by-time">Filter meta queries by time</a></td>
<td></td>
</tr>
@ -1169,7 +1170,72 @@ Note that `SHOW FIELD KEYS` handles field type discrepancies differently from
For more information, see the
[How does InfluxDB handle field type discrepancies across shards?](/influxdb/v1.8/troubleshooting/frequently-asked-questions/#how-does-influxdb-handle-field-type-discrepancies-across-shards).
### Filter meta queries by time
## `SHOW CARDINALITY`
`SHOW CARDINALITY` refers to the group of commands used to estimate or count exactly
the cardinality of measurements, series, tag keys, tag key values, and field keys.
For more information on the `SHOW CARDINALITY` commands,
see the [InfluxQL reference entry](/enterprise_influxdb/v1.9/query_language/spec/#show-cardinality).
### `SHOW FIELD KEY CARDINALITY`
```sql
-- show estimated cardinality of the field key set of current database
SHOW FIELD KEY CARDINALITY
-- show exact cardinality on field key set of specified database
SHOW FIELD KEY EXACT CARDINALITY ON mydb
```
### `SHOW MEASUREMENT KEY CARDINALITY`
```sql
-- show estimated cardinality of measurement set on current database
SHOW MEASUREMENT CARDINALITY
-- show exact cardinality of measurement set on specified database
SHOW MEASUREMENT EXACT CARDINALITY ON mydb
```
### `SHOW SERIES CARDINALITY`
```sql
-- show estimated cardinality of the series on current database
SHOW SERIES CARDINALITY
-- show estimated cardinality of the series on specified database
SHOW SERIES CARDINALITY ON mydb
-- show exact series cardinality
SHOW SERIES EXACT CARDINALITY
-- show series cardinality of the series on specified database
SHOW SERIES EXACT CARDINALITY ON mydb
```
### `SHOW TAG KEY CARDINALITY`
```sql
-- show estimated tag key cardinality
SHOW TAG KEY CARDINALITY
-- show exact tag key cardinality
SHOW TAG KEY EXACT CARDINALITY
```
### `SHOW TAG VALUES CARDINALITY`
```sql
-- show estimated tag key values cardinality for a specified tag key
SHOW TAG VALUES CARDINALITY WITH KEY = "myTagKey"
-- show estimated tag key values cardinality for a specified tag key
SHOW TAG VALUES CARDINALITY WITH KEY = "myTagKey"
-- show exact tag key values cardinality for a specified tag key
SHOW TAG VALUES EXACT CARDINALITY WITH KEY = "myTagKey"
-- show exact tag key values cardinality for a specified tag key
SHOW TAG VALUES EXACT CARDINALITY WITH KEY = "myTagKey"
```
## Filter meta queries by time
When you filter meta queries by time, you may see results outside of your specified time. Meta query results are filtered at the shard level, so results can be approximately as granular as your shard group duration. If your time filter spans multiple shards, you'll get results from all shards with points in the specified time range. To review your shards and timestamps on points in the shard, run `SHOW SHARDS`. To learn more about shards and their duration, see [recommended shard groups durations](/influxdb/v1.8/concepts/schema_and_data_layout/#shard-group-duration-recommendations).