Slow when joining with view - Mailing list pgsql-admin

explain analyze
SELECT x1.id    
FROM (    SELECT id, data->>'open_course_id' oc_id   FROM student_credits    WHERE (data->>'student_id')::BIGINT = '5500'
) x1
JOIN (   SELECT id FROM V_OpenCourse_WithTC        WHERE semester_id = '53'
) x2 ON x1.oc_id::BIGINT = x2.id 

    SELECT id, data->>'open_course_id' oc_id   FROM student_credits    WHERE (data->>'student_id')::BIGINT = '5500'

    SELECT id FROM V_OpenCourse_WithTC        WHERE semester_id = '53'