Column operations change the table contract

What operations.columns is

Column operations are the three transformations that change which columns exist, what they are called, or what types they hold.

They do not filter rows or compute grouped results. Those effects belong to other operation families and should remain separate steps.

What it contains

• select — Keeps an ordered, non-empty list of columns.
• rename — Maps old names to new names.
• cast — Maps columns to supported target types.

Membership, names, and types are different

Keeping the three moves separate makes a pipeline readable. A reviewer can see whether a step narrows the table, changes its vocabulary, or converts its values.

Run the complete example

Copy this manifest from the verified documentation project, then run it from the repository root.

version: "1.0"
transformations:
  steps:
    - cast:
        mapping: {amount: float}
    - rename:
        mapping: {amount: total_amount}
    - select:
        columns: [order_id, customer_id, total_amount, status]

hdrctl run examples/tutorial/dsl-elements -t columns.yaml

  ✅ Pipeline completed successfully in 2.4s
  Rows read   : 30
  Rows written: 30

The relevant command syntax, copied from hdrctl run --help:

hdrctl run [PATH]
  -s, --sources FILE          explicit path to sources.yaml
  -d, --destinations FILE     explicit path to destinations.yaml
  -t, --transformations FILE  explicit path to transformations.yaml
  -P, --param KEY=VALUE       override a parameter, repeatable

Close by

• steps — execution order
• Rows — filtering and sorting
• Compute — creating values
• schema — expected input fields
• Reference — select, rename, cast