Stream Lookup

Description

The Stream Lookup transform type allows you to look up data using information coming from other transforms in the pipeline.

The data coming from the Source transform is first read into memory and is then used to look up data from the main stream.

Since this transform loads the lookup data into memory, it can be an extremely fast way to look up data. However, the entire lookup data set needs to fit in your available memory.

Options

Option	Description
Transform name	Name of the transform this name has to be unique in a single pipeline
Lookup Transform	The Transform name where the lookup data is coming from
The keys to lookup…	Allows you to specify the names of the fields that are used to look up values. Values are always searched using the "equal" comparison
Fields to retrieve	You can specify the names of the fields to retrieve here, as well as the default value in case the value was not found or a new field name in case you didn’t like the old one.
Preserve memory	Encodes rows of data to preserve memory while sorting. (Technical background: Hop will store the lookup data as raw bytes in a custom storage object that uses a hashcode of the bytes as the key. More CPU cost related to calculating the hashcode, less memory needed.)
Key and value are exactly one integer field	Preserves memory while executing a sort by . Note: Works only when "Preserve memory" is checked. Cannot be combined with the "Use sorted list" option.
Use sorted list	Enable to store values using a sorted list; this provides better memory usage when working with data sets containing wide row. Note: Works only when "Preserve memory" is checked. Cannot be combined with the "Key and value are exactly one integer field" option.
Get fields	Automatically fills in the names of all the available fields on the source side (A); you can then delete all the fields you don’t want to use for lookup.
Get lookup fields	Automatically inserts the names of all the available fields on the lookup side (B). You can then delete the fields you don’t want to retrieve

Option

Description

Transform name

Name of the transform this name has to be unique in a single pipeline

Lookup Transform

The Transform name where the lookup data is coming from

The keys to lookup…

Allows you to specify the names of the fields that are used to look up values. Values are always searched using the "equal" comparison

Fields to retrieve

You can specify the names of the fields to retrieve here, as well as the default value in case the value was not found or a new field name in case you didn’t like the old one.

Preserve memory

Encodes rows of data to preserve memory while sorting. (Technical background: Hop will store the lookup data as raw bytes in a custom storage object that uses a hashcode of the bytes as the key. More CPU cost related to calculating the hashcode, less memory needed.)

Key and value are exactly one integer field

Preserves memory while executing a sort by . Note: Works only when "Preserve memory" is checked. Cannot be combined with the "Use sorted list" option.

Use sorted list

Enable to store values using a sorted list; this provides better memory usage when working with data sets containing wide row. Note: Works only when "Preserve memory" is checked. Cannot be combined with the "Key and value are exactly one integer field" option.

Get fields

Automatically fills in the names of all the available fields on the source side (A); you can then delete all the fields you don’t want to use for lookup.

Get lookup fields

Automatically inserts the names of all the available fields on the lookup side (B). You can then delete the fields you don’t want to retrieve

Metadata Injection Support

All fields of this transform support metadata injection. You can use this transform with ETL Metadata Injection to pass metadata to your pipeline at runtime.