PostgreSQL PGCES-02 Exam - Topic 2 Question 3 Discussion

Question

Table "t1" is defined below. Table "t1" has a column "id" of type INTEGER, and a column "name" of type TEXT. t1: The following SQL is executed while client "A" is connected. BEGIN;

SELECT * FROM t1 WHERE id = 2 FOR UPDATE; SELECT * FROM t1 WHERE id = 1 FOR UPDATE; -- (*) While the second 'SELECT' statement, shown with (*), is being executed, a separate client "B" connects and executes the following SQL. Select the correct statement about the execution results. UPDATE t1 SET name = 'turtle' WHERE id = 2; Note: the default transaction isolation level is set to "read committed".

Janine · Accepted Answer

B) The update process for client 'B' is blocked until the current transaction for client 'A' is finished.

Janine · Answer

A) The update process for client 'B' is blocked until the current connection for client 'A' is finished.

Janine · Answer

C) The 'UPDATE' process for client 'B' proceeds regardless of the condition of client 'A'.

Janine · Answer

D) The process of client 'B' immediately generates an error.

Janine · Answer

E) The processes for both clients are blocked, and an error stating that a deadlock has been detected is generated.