Function mz_sql::plan::query::plan_group_by_expr

fn plan_group_by_expr<'a>(
    ecx: &ExprContext<'_>,
    group_expr: &'a Expr<Aug>,
    projection: &'a [(ExpandedSelectItem<'_>, ColumnName)],
) -> Result<(Option<&'a Expr<Aug>>, HirScalarExpr), PlanError>

Plans an expression in a GROUP BY clause.

For historical reasons, PostgreSQL allows GROUP BY expressions to refer to names/expressions defined in the SELECT clause. These special cases are handled by this function; see comments within the implementation for details.