Golang Conn.Query方法代码示例

// Do a simple query to ensure the connection is still usable
func ensureConnValid(t *testing.T, conn *pgx.Conn) {
	var sum, rowCount int32

	rows, err := conn.Query("select generate_series(1,$1)", 10)
	if err != nil {
		t.Fatalf("conn.Query failed: %v", err)
	}
	defer rows.Close()

	for rows.Next() {
		var n int32
		rows.Scan(&n)
		sum += n
		rowCount++
	}

	if rows.Err() != nil {
		t.Fatalf("conn.Query failed: %v", err)
	}

	if rowCount != 10 {
		t.Error("Select called onDataRow wrong number of times")
	}
	if sum != 55 {
		t.Error("Wrong values returned")
	}
}

// This function uses a postgresql 9.6 specific column
func getConfirmedFlushLsnFor(t *testing.T, conn *pgx.Conn, slot string) string {
	// Fetch the restart LSN of the slot, to establish a starting point
	rows, err := conn.Query(fmt.Sprintf("select confirmed_flush_lsn from pg_replication_slots where slot_name='%s'", slot))
	if err != nil {
		t.Fatalf("conn.Query failed: %v", err)
	}
	defer rows.Close()

	var restartLsn string
	for rows.Next() {
		rows.Scan(&restartLsn)
	}
	return restartLsn
}

func TestPoolReleaseDiscardsDeadConnections(t *testing.T) {
	t.Parallel()

	// Run timing sensitive test many times
	for i := 0; i < 50; i++ {
		func() {
			maxConnections := 3
			pool := createConnPool(t, maxConnections)
			defer pool.Close()

			var c1, c2 *pgx.Conn
			var err error
			var stat pgx.ConnPoolStat

			if c1, err = pool.Acquire(); err != nil {
				t.Fatalf("Unexpected error acquiring connection: %v", err)
			}
			defer func() {
				if c1 != nil {
					pool.Release(c1)
				}
			}()

			if c2, err = pool.Acquire(); err != nil {
				t.Fatalf("Unexpected error acquiring connection: %v", err)
			}
			defer func() {
				if c2 != nil {
					pool.Release(c2)
				}
			}()

			if _, err = c2.Exec("select pg_terminate_backend($1)", c1.Pid); err != nil {
				t.Fatalf("Unable to kill backend PostgreSQL process: %v", err)
			}

			// do something with the connection so it knows it's dead
			rows, _ := c1.Query("select 1")
			rows.Close()
			if rows.Err() == nil {
				t.Fatal("Expected error but none occurred")
			}

			if c1.IsAlive() {
				t.Fatal("Expected connection to be dead but it wasn't")
			}

			stat = pool.Stat()
			if stat.CurrentConnections != 2 {
				t.Fatalf("Unexpected CurrentConnections: %v", stat.CurrentConnections)
			}
			if stat.AvailableConnections != 0 {
				t.Fatalf("Unexpected AvailableConnections: %v", stat.CurrentConnections)
			}

			pool.Release(c1)
			c1 = nil // so it doesn't get released again by the defer

			stat = pool.Stat()
			if stat.CurrentConnections != 1 {
				t.Fatalf("Unexpected CurrentConnections: %v", stat.CurrentConnections)
			}
			if stat.AvailableConnections != 0 {
				t.Fatalf("Unexpected AvailableConnections: %v", stat.CurrentConnections)
			}
		}()
	}
}