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Dimension Table
Dimension tables in Apache Pinot.
Dimension tables are a special kind of offline tables from which data can be looked up via the lookup UDF, providing join like functionality.
Dimension tables are replicated on all the hosts for a given tenant to allow faster lookups.
To mark an offline table as a dim table, isDimTable should be set to true and segmentsConfig.segementPushType should be set to REFRESH in the table config as shown below:
{
"OFFLINE": {
"tableName": "dimBaseballTeams_OFFLINE",
"tableType": "OFFLINE",
"segmentsConfig": {
"schemaName": "dimBaseballTeams",
"segmentPushType": "REFRESH"
},
"metadata": {},
"quota": {
"storage": "200M"
},
"isDimTable": true
}
}
As dimension tables are used to perform lookups of dimension values, they are required to have a primary key (can be a composite key).
{
"dimensionFieldSpecs": [
{
"dataType": "STRING",
"name": "teamID"
},
{
"dataType": "STRING",
"name": "teamName"
}
],
"schemaName": "dimBaseballTeams",
"primaryKeyColumns": ["teamID"]
}
When a table is marked as a dimension table, it will be replicated on all the hosts, which means that these tables must be small in size.
The maximum size quota for a dimension table in a cluster is controlled by the controller.dimTable.maxSize controller property. Table creation will fail if the storage quota exceeds this maximum size.
A dimension table cannot be part of a hybrid table.
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