[I] Add window function use cases to the TPC-DS example [ossie]

["fanruan-tuco (via GitHub)" <gi...@apache.org>]

fanruan-tuco opened a new issue, #324:
URL: https://github.com/apache/ossie/issues/324

   ## Problem
   
   Window functions are already defined in both the [Expression Language proposal](https://docs.google.com/document/d/1Jn98kHWsnbvo1MycQBAnWirGTwRmw-DWaen7coNCYWA/edit?tab=t.0) and the [core expression language specification](https://github.com/apache/ossie/blob/main/core-spec/expression_language.md#window-functions). The specification covers ranking functions, offset functions, and window aggregations, but the canonical [`examples/tpcds_semantic_model.yaml`](https://github.com/apache/ossie/blob/main/examples/tpcds_semantic_model.yaml) currently demonstrates only regular aggregate metrics.
   
   Without model-level examples, implementers and users do not have a concrete reference for expressing common analytical use cases, including ordering, partitioning, explicit window frames, field qualification across relationships, and the expected query grain.
   
   ## Proposed change
   
   Add a small, representative set of validated ANSI SQL window-function use cases to `examples/tpcds_semantic_model.yaml`, using the existing TPC-DS datasets and relationships. Suggested cases:
   
   - Running/cumulative sales through each calendar date (window aggregation)
   - Sales rank by brand or store (ranking function)
   - Sales change versus the previous period (offset function such as `LAG`)
   
   For example, a cumulative sales metric could be expressed as:
   
   ```yaml
   - name: cumulative_sales
     expression:
       dialects:
         - dialect: ANSI_SQL
           expression: SUM(store_sales.ss_ext_sales_price) OVER (ORDER BY date_dim.d_date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
     description: Running total of sales revenue through each calendar date
     datatype: Decimal
   ```
   
   ## Acceptance criteria
   
   - The TPC-DS example includes window-function use cases covering window aggregation and representative ranking/offset behavior.
   - Cumulative calculations use an explicit frame so the boundary semantics are clear.
   - Each example documents its expected grouping/grain in the description when needed.
   - All added expressions pass `validation/validate.py`.
   - If any window-function category cannot be represented at the current metric or field level, the supported placement and limitation are documented instead.


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Re: [I] Add window function use cases to the TPC-DS example [ossie]

["jbonofre (via GitHub)" <gi...@apache.org>]

jbonofre closed issue #324: Add window function use cases to the TPC-DS example
URL: https://github.com/apache/ossie/issues/324


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