how should to manage nested SQL in plpgsql-parser

[pyramation]

Seems that the PLpgSQL_expr is a string, and the parser doesn't handle sub expressions.

https://gist.github.com/pyramation/6c8ae2da6593c643eec745f1f9019bfc

                  "default_val": {
                      "PLpgSQL_expr": {
                        "query": "(random() - 0.5) * 0.02",
                        "parseMode": 2
                      }
                    }
...

  "PLpgSQL_expr": {
                        "query": "GREATEST(LEAST(p_discount_rate, 0.50), 0)",
                        "parseMode": 2
                      }

...


 "sqlstmt": {
                                "PLpgSQL_expr": {
                                  "query": "WITH base AS (\n    SELECT\n      o.id,\n      o.total_amount::numeric AS total_amount,\n      o.currency,\n      o.created_at\n    FROM app_public.app_order o\n    WHERE o.org_id = p_org_id\n      AND o.user_id = p_user_id\n      AND o.created_at >= p_from_ts\n      AND o.created_at <  p_to_ts\n      AND o.total_amount::numeric >= v_min_total\n      AND o.currency = p_currency\n    ORDER BY o.created_at DESC\n    LIMIT p_max_rows\n  ),\n  totals AS (\n    SELECT\n      count(*)::int AS orders_scanned,\n      COALESCE(sum(total_amount), 0) AS gross_total,\n      COALESCE(avg(total_amount), 0) AS avg_total\n    FROM base\n  )\n  SELECT\n    t.orders_scanned,\n    t.gross_total,\n    t.avg_total\n                                                      FROM totals t",
                                  "parseMode": 0
                                }
                              },