Slow when joining with view

[Kiswono Prayogo <kiswono@xxxxxxxxx>]

The case https://stackoverflow.com/questions/30861967/slow-when-joining-with-view

It doesn't make sense that this query took 10s:

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 

when both of its components took less than 100ms:

    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'

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Best Regards,
Kiswono P
GB