用堆疊診斷強化例外處理
PostgreSQL 的交易與錯誤處理
Jason Myers
Principal Engineer
擷取更多錯誤資訊
DO $$
BEGIN
UPDATE inventory SET cost = 35.0 WHERE name = 'Macaron';
UPDATE inventory SET cost = 3.50 WHERE name = 'Panellets';
EXCEPTION
WHEN others THEN
INSERT INTO errors (msg) VALUES ('Max cost is 10!');
RAISE INFO 'Max cost is 10!';
END;
$$ language 'plpgsql';
使用堆疊診斷
DO $$ DECLARE exc_message text; exc_detail text;BEGIN UPDATE inventory SET cost = 35.0 WHERE name = 'Macaron'; UPDATE inventory SET cost = 3.50 WHERE name = 'Panellets';EXCEPTION WHEN others THEN GET STACKED DIAGNOSTICS exc_message = MESSAGE_TEXT, exc_detail = PG_EXCEPTION_DETAIL; INSERT INTO errors (msg, detail) VALUES (exc_message, exc_detail); RAISE INFO 'Exception Messaage: % | Exception Details: %', exc_message, exc_detail; END$$;
診斷輸出範例
INFO: Exception Messaage: new row for relation "inventory" violates check constraint
"cost_check" | Exception Details: Failing row contains (7, 35, Macaron).
DO
postgres=# \x on
Expanded display is on.
postgres=# select msg, detail from errors;
-[ RECORD 1 ]-------------------------------------------------------------------
msg | new row for relation "inventory" violates check constraint "cost_check"
detail | Failing row contains (7, 35, Macaron).
可以取得哪些資訊？
| Name | Description |
|---|---|
| RETURNED_SQLSTATE | 例外的 SQLSTATE 錯誤代碼 |
| COLUMN_NAME | 與例外相關的欄位名稱 |
| CONSTRAINT_NAME | 與例外相關的約束名稱 |
| MESSAGE_TEXT | 例外的主訊息文字 |
| PG_EXCEPTION_DETAIL | 例外的詳細訊息（若有） |
1 https://www.postgresql.org/docs/12/plpgsql-control-structures.html
更多診斷欄位
| Name | Description |
|---|---|
| PG_DATATYPE_NAME | 與例外相關的資料型別名稱 |
| TABLE_NAME | 與例外相關的資料表名稱 |
| SCHEMA_NAME | 與例外相關的結構描述名稱 |
| PG_EXCEPTION_HINT | 例外的提示訊息文字（若有） |
| PG_EXCEPTION_CONTEXT | 例外發生當下呼叫堆疊的文字行 |
一起來練習吧！
PostgreSQL 的交易與錯誤處理
