minimize and maximize

minimize and maximize reduce by taking the smallest or largest seen value, respectively.

collections:
  - name: example/reductions/min-max
    schema:
      type: object
      reduce: { strategy: merge }
      properties:
        key: { type: string }
        min: { reduce: { strategy: minimize } }
        max: { reduce: { strategy: maximize } }
      required: [key]
    key: [/key]

tests:
  "Expect we can min/max values":
    - ingest:
        collection: example/reductions/min-max
        documents:
          - { key: "key", min: 32, max: "abc" }
          - { key: "key", min: 42, max: "def" }
    - verify:
        collection: example/reductions/min-max
        documents:
          - { key: "key", min: 32, max: "def" }

minimize and maximize can also take a key, which is one or more JSON pointers that are relative to the reduced location. Keys make it possible to minimize and maximize over complex types by ordering over an extracted composite key.

In the event that a right-hand side document key equals the current left-hand side minimum or maximum, the documents are deeply merged. This can be used to, for example, track not just the minimum value but also the number of times it’s been seen:

collections:
  - name: example/reductions/min-max-key
    schema:
      type: object
      reduce: { strategy: merge }
      properties:
        key: { type: string }
        min:
          $anchor: min-max-value
          type: array
          items:
            - type: string
            - type: number
              reduce: { strategy: sum }
          reduce:
            strategy: minimize
            key: [/0]
        max:
          $ref: "#min-max-value"
          reduce:
            strategy: maximize
            key: [/0]
      required: [key]
    key: [/key]

tests:
  "Expect we can min/max values using a key extractor":
    - ingest:
        collection: example/reductions/min-max-key
        documents:
          - { key: "key", min: ["a", 1], max: ["a", 1] }
          - { key: "key", min: ["c", 2], max: ["c", 2] }
          - { key: "key", min: ["b", 3], max: ["b", 3] }
          - { key: "key", min: ["a", 4], max: ["a", 4] }
    - verify:
        collection: example/reductions/min-max-key
        documents:
          # Min of equal keys ["a", 1] and ["a", 4] => ["a", 5].
          - { key: "key", min: ["a", 5], max: ["c", 2] }