dim-table.md

description
Batch ingestion of data into Apache Pinot using dimension tables.

Dimension table

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. 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.

A dimension table cannot be part of a hybrid table.

Configure dimension tables using following properties in the table configuration:

• isDimTable: Set to true.
• segmentsConfig.segmentPushType: Set to REFRESH.
• dimensionTableConfig.disablePreload: By default, dimension tables are preloaded to allow for fast lookups. Set to true to trade off speed for memory by storing only the segment reference and docID. Otherwise, the whole row is stored in the Dimension table hash map.
• controller.dimTable.maxSize: Determines the maximum size quota for a dimension table in a cluster. Table creation will fail if the storage quota exceeds this maximum size.
• dimensionFieldSpecs: To look up dimension values, dimension tables need a primary key. For details, see dimensionFieldSpecs.

Example dimension table configuration

{
  "OFFLINE": {
    "tableName": "dimBaseballTeams_OFFLINE",
    "tableType": "OFFLINE",
    "segmentsConfig": {
      "schemaName": "dimBaseballTeams",
      "segmentPushType": "REFRESH"
    },
    "metadata": {},
    "quota": {
      "storage": "200M"
    },
    "isDimTable": true,
    "dimensionTableConfig": {
      "disablePreload": true
    }
  }
}

Example table schema configuration

{
  "dimensionFieldSpecs": [
    {
      "dataType": "STRING",
      "name": "teamID"
    },
    {
      "dataType": "STRING",
      "name": "teamName"
    }
  ],
  "schemaName": "dimBaseballTeams",
  "primaryKeyColumns": ["teamID"]
}