Function try_plan_in_subquery

nodedb-sql/src/planner/subquery.rs:154–197

Try to plan `col IN (SELECT col2 FROM tbl ...)` as a semi/anti join.

(
    outer_expr: &Expr,
    subquery: &ast::Query,
    negated: bool,
    catalog: &dyn SqlCatalog,
    functions: &FunctionRegistry,
    temporal: crate::TemporalScope,
)

/// Try to plan `col IN (SELECT col2 FROM tbl ...)` as a semi/anti join.
fn try_plan_in_subquery(
    outer_expr: &Expr,
    subquery: &ast::Query,
    negated: bool,
    catalog: &dyn SqlCatalog,
    functions: &FunctionRegistry,
    temporal: crate::TemporalScope,
) -> Result<Option<SubqueryJoin>> {
    // Extract outer column name.
    let outer_col = match outer_expr {
        Expr::Identifier(ident) => normalize_ident(ident),
        Expr::CompoundIdentifier(parts) if parts.len() >= 3 => {
            let qualified: String = parts
                .iter()
                .map(normalize_ident)
                .collect::<Vec<_>>()
                .join(".");
            return Err(SqlError::Unsupported {
                detail: format!(
                    "schema-qualified column reference '{qualified}': {SCHEMA_QUALIFIED_MSG}"
                ),
            });
        }
        Expr::CompoundIdentifier(parts) if parts.len() == 2 => normalize_ident(&parts[1]),
        _ => return Ok(None), // Complex expression, can't rewrite.
    };

    // Plan the inner SELECT.
    let inner_plan = super::select::plan_query(subquery, catalog, functions, temporal)?;

    // Extract the projected column from the inner plan.
    let inner_col = extract_single_projected_column(subquery)?;

    Ok(Some(SubqueryJoin {
        outer_column: outer_col,
        inner_plan,
        inner_column: inner_col,
        join_type: if negated {
            JoinType::Anti
        } else {
            JoinType::Semi
        },
    }))
}

/// Extract the single column name from a subquery's SELECT list.
///