DuckDB analytical expression helpers for Ecto queries.

These macros wrap DuckDB-specific SQL functions in Ecto.Query.API.fragment/1 so analytical queries can stay in Ecto's query DSL instead of scattering raw fragment strings across application code.

import Ecto.Query
import QuackDB.Ecto.Analytics

from(event in "events",
  group_by: event.category,
  select: %{
    category: event.category,
    median_score: median(event.score),
    p95_score: quantile_cont(event.score, 0.95),
    scores: duckdb_list(event.score)
  }
)

Helpers only build expressions. DuckDB clauses that are not representable in Ecto's AST, such as PIVOT, UNPIVOT, QUALIFY, GROUPING SETS, and USING SAMPLE, should still be sent as raw SQL.