The Lookup UDF Join is only supported with the single-stage query engine (v1). For more information about using JOINs with the multi-stage query engine, see JOINs.
Lookup UDF is used to get dimension data via primary key from a dimension table allowing a decoration join functionality. Lookup UDF can only be used with a dimension table in Pinot.

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Syntax

The UDF function syntax is listed as below: 
lookupUDFSpec:
    LOOKUP
    '('
    '''dimTable'''
    '''dimColToLookup'''
    [ '''dimJoinKey''', factJoinKey ]*
    ')'
  • dimTable Name of the dim table to perform the lookup on.
  • dimColToLookUp The column name of the dim table to be retrieved to decorate our result.
  • dimJoinKey The column name on which we want to perform the lookup i.e. the join column name for dim table.
  • factJoinKey The column name on which we want to perform the lookup against e.g. the join column name for fact table
  • all the dim-table-related expressions are expressed as literal strings, this is the LOOKUP UDF syntax limitation: we cannot express column identifier which doesn’t exist in the query’s main table, which is the factTable table.
  • the syntax definition of [ '''dimJoinKey''', factJoinKey ]* indicates that if there are multiple dim partition columns, there should be multiple join key pair expressed.

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Examples

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Single-partition-key-column Example

Consider the table baseballStats
ColumnType
playerIDSTRING
yearIDINT
teamIDSTRING
leagueSTRING
playerNameSTRING
playerStintINT
numberOfGamesINT
numberOfGamesAsBatterINT
AtBattingINT
runsINT
And the dim table dimBaseballTeams
ColumnType
teamIDSTRING
teamNameSTRING
teamAddressSTRING
Valid queries include the following:

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Dim-Fact LOOKUP example

SELECT 
  playerName, 
  teamID, 
  LOOKUP('dimBaseballTeams', 'teamName', 'teamID', teamID) AS teamName, 
  LOOKUP('dimBaseballTeams', 'teamAddress', 'teamID', teamID) AS teamAddress
FROM baseballStats
playerNameteamIDteamNameteamAddress
David AllanBOSBoston Red Caps/Beaneaters (from 1876–1900) or Boston Red Sox (since 1953)4 Jersey Street, Boston, MA
David AllanCHAnullnull
David AllanSEASeattle Mariners (since 1977) or Seattle Pilots (1969)1250 First Avenue South, Seattle, WA
David AllanSEASeattle Mariners (since 1977) or Seattle Pilots (1969)1250 First Avenue South, Seattle, WA

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Self LOOKUP example

SELECT 
  teamID, 
  teamName AS nameFromLocal,
  LOOKUP('dimBaseballTeams', 'teamName', 'teamID', teamID) AS nameFromLookup
FROM dimBaseballTeams
teamIDnameFromLocalnameFromLookup
ANAAnaheim AngelsAnaheim Angels
ARIArizona DiamondbacksArizona Diamondbacks
ATLAtlanta BravesAtlanta Braves
BALBaltimore Orioles (original- 1901–1902 current- since 1954)Baltimore Orioles (original- 1901–1902 current- since 1954)

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Complex-partition-key-columns Example

Consider a single dimension table with the following schema: BILLING SCHEMA
ColumnType
customerIdINT
creditHistorySTRING
firstNameSTRING
lastNameSTRING
isCarOwnerBOOLEAN
citySTRING
maritalStatusSTRING
buildingTypeSTRING
missedPaymentSTRING
billingMonthSTRING

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Self LOOKUP example

select 
  customerId,
  missedPayment, 
  LOOKUP('billing', 'city', 'customerId', customerId, 'creditHistory', creditHistory) AS lookedupCity 
from billing
customerIdmissedPaymentlookedupCity
341PaidPalo Alto
374PaidMountain View
398PaidPalo Alto
427PaidCupertino
435PaidCupertino

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Usage

  • The data return type of the UDF will be that of the dimColToLookUp column type.
  • When multiple primary key columns are used for the dimension table (e.g. composite primary key), ensure that the order of keys appearing in the lookup() UDF is the same as the order defined in the primaryKeyColumns from the dimension table schema.