คำแนะนำสำหรับการจัดการ nested exceptions

Transactions and Error Handling in PostgreSQL

Jason Myers

Principal Engineer

จำลอง savepoint ด้วย nested blocks

DO $$
BEGIN
    -- Block 1
    BEGIN
        UPDATE inventory SET cost = 2.33 WHERE name = 'Linga';
        UPDATE inventory SET cost = 2.33 WHERE name = 'Petit-Beurre';
    EXCEPTION
    WHEN others THEN
       INSERT INTO errors (msg) VALUES ('Max cost is 10!');
       RAISE INFO 'Max cost is 10!';
    END;

จำลอง savepoint — Block 2

-- Block 2
    BEGIN
        UPDATE inventory SET cost = 35.0 WHERE name = 'Macaron';
    EXCEPTION
    WHEN others THEN
       INSERT INTO errors (msg) VALUES ('Max cost is 10!');
       RAISE INFO 'Max cost is 10!';
    END; 
END;
$$ language 'plpgsql';

Nested blocks กับ stacked diagnostics

DO $$
DECLARE
   exc_message text;
   exc_detail text;
   exc_context text;
BEGIN
    -- Block 1
    BEGIN
        UPDATE inventory SET cost = 2.33 WHERE name = 'Linga';
        UPDATE inventory SET cost = 2.33 WHERE name = 'Petit-Beurre';
    EXCEPTION
    WHEN others THEN
        GET STACKED DIAGNOSTICS exc_message = MESSAGE_TEXT,
                                exc_detail = PG_EXCEPTION_DETAIL,
                                exc_context = PG_EXCEPTION_CONTEXT;
       INSERT INTO errors (msg,detail, context) 
           VALUES (exc_message, exc_detail, exc_context);
    END; 
    -- Block 2
    BEGIN
        UPDATE inventory SET cost = 35.0 WHERE name = 'Macaron';
    EXCEPTION
    WHEN others THEN
       GET STACKED DIAGNOSTICS exc_message = MESSAGE_TEXT,
                               exc_detail = PG_EXCEPTION_DETAIL,
                               exc_context = PG_EXCEPTION_CONTEXT;
       INSERT INTO errors (msg,detail, context) 
           VALUES (exc_message, exc_detail, exc_context);
    END; 
END$$;

Nested blocks กับ stacked diagnostics

DO $$
DECLARE
   exc_message text;
   exc_detail text;
   exc_context text;
BEGIN

Nested blocks กับ stacked diagnostics: block 2

    -- Block 1
    BEGIN
        UPDATE inventory SET cost = 2.33 WHERE name = 'Linga';
        UPDATE inventory SET cost = 2.33 WHERE name = 'Petit-Beurre';
    EXCEPTION
    WHEN others THEN
        GET STACKED DIAGNOSTICS exc_message = MESSAGE_TEXT,
                                exc_detail = PG_EXCEPTION_DETAIL,
                                exc_context = PG_EXCEPTION_CONTEXT;
       INSERT INTO errors (msg,detail, context) 
           VALUES (exc_message, exc_detail, exc_context);
    END;

Nested blocks กับ stacked diagnostics: block 2

-- Block 2
    BEGIN
        UPDATE inventory SET cost = 35.0 WHERE name = 'Macaron';
    EXCEPTION
    WHEN others THEN
       GET STACKED DIAGNOSTICS exc_message = MESSAGE_TEXT,
                               exc_detail = PG_EXCEPTION_DETAIL,
                               exc_context = PG_EXCEPTION_CONTEXT;
       INSERT INTO errors (msg,detail, context) 
           VALUES (exc_message, exc_detail, exc_context);
    END; 
END$$;

ผลลัพธ์

INFO:  Message: new row for relation "inventory" violates check constraint 
"cost_check" | Details: Failing row contains (7, 35, Macaron). | Context SQL 
statement "UPDATE inventory SET cost = 35.0 WHERE name = 'Macaron'"
PL/pgSQL function inline_code_block line 23 at SQL statement
DO
postgres=# \x on
Expanded display is on.
postgres=# select * from errors;
-[ RECORD 1 ]---------------------------------------------------------------------
error_id | 15
state    |
msg      | new row for relation "inventory" violates check constraint "cost_check"
detail   | Failing row contains (7, 35, Macaron).
context  | SQL statement "UPDATE inventory SET cost = 35.0 WHERE name = 'Macaron'"+
         | PL/pgSQL function inline_code_block line 23 at SQL statement

Custom exception handling เทียบกับ stacked diagnostics

Custom

บริบทของข้อผิดพลาดชัดเจน
เงื่อนไขข้อผิดพลาดที่คาดไว้
ข้อความ error มาตรฐานกว้างเกินไป

Stacked Diagnostics

ต้องการบริบทเพิ่มเติมสำหรับข้อผิดพลาด
มีเงื่อนไขข้อผิดพลาดหลายกรณี
การดีบัก
การจัดการ exception แบบทั่วไป

มาฝึกกันเถอะ!

Transactions and Error Handling in PostgreSQL