What is sparse lookup?

What is sparse lookup?

A sparse lookup is also known as a direct lookup because the lookup is performed directly on the database. Typically, you use a sparse lookup when the target table is too large to fit in memory. You can also use the sparse lookup method for real-time jobs. You can use the sparse lookup method only in parallel jobs.

Why is the sparse lookup in DataStage faster than normal lookup?

Sparse Lookup directly hits the database. If the input stream data is less and reference data is more like 1:100 or more in such cases sparse lookup is better. Sparse lookup sends individual sql statements for every incoming row. (Imagine if the reference data is huge).

What is the use of lookup stage in Datastage?

The Lookup stage is a processing stage that is used to perform lookup operations on a data set read into memory from any other Parallel job stage that can output data.

Which is sparse look up in DataStage ETL?

Sparse Look Up Let’s study them in detail one by one. 1. Range LooK Up: As the name suggest, it performs look up operation for particular Range only. To understand this Range Look Up operation, consider a following scenario of two input links. Suppose there are two tables of having record for employee expected salary and actual salary as below.

When to use sparse lookup in SQL Server?

Remember, sparse lookup is only available when the database stage is directly connected to the reference link, with no intermediate stages between lookup and database stage. It is important to note that the individual SQL statements required by a Sparse Lookup are an expensive operation from a performance perspective.

When to use sparse lookup or join in DataStage?

You have been working on DataStage and most of the times you have used Lookup stage for lookup data from reference link. Suddenly you heard about Sparse lookup and now you are thinking like what is the difference between normal lookup and sparse lookup? That’s simple.

How is data read used in a lookup stage?

Data read by any database stage can serve as the reference input to a Lookup stage. By default, this reference data from database is being loaded into memory like any other reference link that used in lookup stage.