---json
{
    "page_id": "k6rc1cn2xhcl5jsnopfh0"
}
---
====== How to retrieve a third column from a data set generator ? ======


===== About =====
This howto will show you how to use the [[:docs:generator:data-set-meta|data set meta generator]] to retrieve a meta column (ie third column) from a data set defined in a data set generator (ie [[:docs:generator:data-set|data set]] or [[:docs:generator:entity|entity]] generator)


===== Example =====


==== Data Set ====

In this example, the data set is the [[:docs:generator:entity|region entity]]

We want to generate the data
  * for the `region` column
  * but also returns the `code` column

The content of the data set is:
<unit>
<code bash>
tabul data head region/region.csv@entity
</code>
<console>
The first 10 rows of the data resource (region/region.csv@entity):
region     code
--------   ----
Africa     2
Americas   19
Asia       142
Europe     150
Oceania    9
</console>
</unit>

==== Generator ====

Using this dataset, we can generate generates 10 `regions` with this [[:docs:resource:generator|generator file]].
<unit>
<file yaml generator/dataset-meta-type--generator.yml>
kind: generator
spec:
  MaxRecordCount: 10
  Columns:
    - name: region
      Type: varchar
      data-supplier:
        type: entity
        arguments:
          name: region
    - name: code
      Type: varchar
      data-supplier:
        type: data-set-meta # the type
        arguments:
          column-data-set: region # refer to the first column that contains an entity generator
          column: code # the column in the region entity data set to return

</file>
</unit>

==== Printing the data ====

You can see/generate the output with [[:docs:tabul:data:print|tabul print]]

<unit>
<code bash>
tabul data print generator/dataset-meta-type--generator.yml@howto
</code>
<console>
region     code
--------   ----
Oceania    9
Asia       142
Africa     2
Africa     2
Europe     150
Americas   19
Africa     2
Americas   19
Americas   19
Asia       142
</console>
</unit>