GSoC 2026: Add support for generate_series in postgres (Draft Proposal Feedback)

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Following recent feedback on this forum post - Post
I’ve restructured my proposal to prioritize the foundational ORM primitives rather than jumping directly to SRF routing.

Revised phased approach:

  1. CompositeField — Enabling expressions to declare tuple return types. The existing ColPairs (composite PK support) and allows_composite_expressions flag show the ORM is already moving in this direction.
  2. output_field on alias_map members — Having BaseTable and Join define their own output_field so that lookup resolution in names_to_path() can transition from self.model → self.base_table.output_field. This delegates SQL generation to expressions instead of hardcoding it in the compiler.
  3. SRF support via LATERAL JOIN — With the above foundations, a TableValuedFunction alias_map member naturally integrates: add_annotation() detects set_returning=True, routes the expression to alias_map with a CompositeField output, and replaces the annotation with a Col reference. The compiler emits LATERAL generate_series(...) in the FROM clause.

One specific question: Once Phase 2 makes alias_map members self-describing via

output_field, would you expect TableValuedFunction to integrate through Query.join() (with a lightweight adaptation for members that lack join_cols), or is direct alias_map insertion with manual refcount management the cleaner approach? TVFs don’t participate in join deduplication or promotion, so I lean toward direct insertion — but I’d value your perspective on long-term maintainability.

Updated AST ( Abstract Syntax Tree )

User writes:
.annotate(series=GenerateSeries(1, 10)).filter(series__gt=5)
                               │
                               ▼
                  ┌────────────────────────┐
                  │ Query.add_annotation() │
                  │ (set_returning=True)   │
                  └────────────┬───────────┘
                               │
            ┌──────────────────┴──────────────────┐
            ▼                                     ▼
  [Phase 2: FROM clause]                [Phase 1: SELECT/WHERE]
  alias_map["series"] =                 annotations["series"] =
  TableValuedFunction(                  Col("series",
    expr=GenerateSeries(1, 10),           CompositeField(
    alias="series",                         IntegerField("value")
    output_field=CompositeField(          )
      IntegerField("value")             )
    )
  )                                               │
            │                                     │
            ▼                                     ▼
  get_from_clause() iterates            resolve_ref("series")
  alias_map, calls as_sql()             returns the Col object
            │                                     │
            ▼                                     ▼
  LATERAL generate_series(1, 10)        "series"."value" > 5
  AS "series"("value")
 
 ─────────────────────────────────────────────────────────────
 FINAL SQL:
 SELECT "myapp_model"."id", "series"."value"
 FROM "myapp_model",
      LATERAL generate_series(1, 10) AS "series"("value")
 WHERE "series"."value" > 5
 ─────────────────────────────────────────────────────────────