Combine brings in a second declared source

What operations.combine is

Combine operations bring a second source into the current transformation frame.

The transformation engine does not open that source itself. The runner resolves right, loads its rows, and injects them before join, merge, or union executes.

What it contains

• join — Matches rows with inner, left, right, or outer semantics.
• merge — Reconciles rows by a required key, optionally deleting unmatched left rows.
• union — Stacks compatible rows and optionally removes duplicates.

Right is prepared before the operation

A two-frame operation still has one transformation input. The runner turns right into ready rows first, so the engine receives two frames rather than a connector configuration.

Run the complete example

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

version: "1.0"
transformations:
  steps:
    - union:
        right: src_orders_extra
        distinct: false

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

  ✅ Pipeline completed successfully in 2.7s
  Rows read   : 30
  Rows written: 34

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

• sources.yaml — declaring right
• steps — current frame order
• Aggregate — grouped summaries
• Reshape — layout changes
• Reference — join, merge, union