Function Pushdown

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The following examples contrast the query plans when a function cannot be pushed down. In the right column, an extra step appears in the query plan. This extra step appears because the data source does not support the MD5 function. Data Virtuality compensated for the lack of MD5 functionality by implementing it internally.

Example 1: Pushdown supported

SQL

SELECT
    md5("Name")
FROM
    "mssql_advworks_2019.AdventureWorks2019.HumanResources.Shift"
;;

SQL

SELECT md5(g_0.Name) FROM mssql_advworks_2019.AdventureWorks2019.HumanResources.Shift AS g_0

Example 2: Pushdown NOT supported

SQL

SELECT
    md5("salespersonid")
FROM
    "no_pushdown.SalesOrderHeader_ALL"
;;

SQL

md5(no_pushdown.SalesOrderHeader_All.salespersonid)

SQL

SELECT no_pushdown.SalesOrderHeader_All.salespersonid FROM no_pushdown.SalesOrderHeader_All