Function extract_aggregates

nodedb-sql/src/aggregate_walk.rs:51–68

Extract every aggregate function call from `expr`, binding each to the given output `alias`. Nested aggregates (e.g. `SUM(AVG(x))`, which is illegal SQL in Postgres and most other systems) are reported as a planner error rather than silently double-extracted.

(
    expr: &Expr,
    alias: &str,
    functions: &FunctionRegistry,
)

/// which is illegal SQL in Postgres and most other systems) are
/// reported as a planner error rather than silently double-extracted.
pub fn extract_aggregates(
    expr: &Expr,
    alias: &str,
    functions: &FunctionRegistry,
) -> Result<Vec<AggregateExpr>> {
    let mut extractor = AggregateExtractor {
        functions,
        alias,
        inside_aggregate: 0,
        out: Vec::new(),
        error: None,
    };
    let _ = expr.visit(&mut extractor);
    if let Some(e) = extractor.error {
        return Err(e);
    }
    Ok(extractor.out)
}

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