Usage
view: view_name {
measure: field_name {
approximate: yes
}
}
|
Hierarchy
approximate |
Possible Field Types
Measure
Accepts
A Boolean (yes or no)
|
Definition
See the Dialect support for
approximatesection on this page for the list of dialects that supportindexes.
The approximate parameter lets you use approximate counting with measures of type: count and type: count_distinct. With large datasets, approximate counts can be much faster than exact counts and are typically within a few percent of the actual value. Please check your SQL dialect's documentation to understand the speed and accuracy tradeoffs of this method.
measure: apx_unique_count {
type: count_distinct
approximate: yes # default value is no
sql: ${id} ;;
}
-
Turning on approximate with a measure of type: count might seem unnecessary, because the approximate counting feature applies only to distinct counts. However, there are some situations when Looker automatically turns measures of type: count into a distinct count of a primary key to provide accurate results for joined views. In those situations, approximate counting may be useful.
Dialect support for approximate
The ability to use approximate depends on the database dialect your Looker connection is using. In the latest version of Looker, the following dialects support approximate:
| Dialect | Supported? |
|---|---|
| Actian Avalanche | No |
| Amazon Athena | Yes |
| Amazon Aurora MySQL | No |
| Amazon Redshift | Yes |
| Apache Druid | No |
| Apache Druid 0.13+ | No |
| Apache Druid 0.18+ | No |
| Apache Hive 2.3+ | No |
| Apache Hive 3.1.2+ | No |
| Apache Spark 3+ | No |
| ClickHouse | No |
| Cloudera Impala 3.1+ | Yes |
| Cloudera Impala 3.1+ with Native Driver | Yes |
| Cloudera Impala with Native Driver | Yes |
| DataVirtuality | No |
| Databricks | No |
| Denodo 7 | No |
| Denodo 8 | No |
| Dremio | No |
| Dremio 11+ | No |
| Exasol | No |
| Firebolt | No |
| Google BigQuery Legacy SQL | Yes |
| Google BigQuery Standard SQL | Yes |
| Google Cloud PostgreSQL | No |
| Google Cloud SQL | No |
| Google Spanner | No |
| Greenplum | No |
| HyperSQL | No |
| IBM Netezza | No |
| MariaDB | No |
| Microsoft Azure PostgreSQL | No |
| Microsoft Azure SQL Database | No |
| Microsoft Azure Synapse Analytics | No |
| Microsoft SQL Server 2008+ | No |
| Microsoft SQL Server 2012+ | No |
| Microsoft SQL Server 2016 | No |
| Microsoft SQL Server 2017+ | No |
| MongoBI | No |
| MySQL | No |
| MySQL 8.0.12+ | No |
| Oracle | No |
| Oracle ADWC | No |
| PostgreSQL 9.5+ | No |
| PostgreSQL pre-9.5 | No |
| PrestoDB | Yes |
| PrestoSQL | Yes |
| SAP HANA | No |
| SAP HANA 2+ | No |
| SingleStore | No |
| SingleStore 7+ | No |
| Snowflake | No |
| Teradata | No |
| Trino | Yes |
| Vector | No |
| Vertica | No |