Full table scan: 300 million rows - Mailing list pgsql-novice

Select  avg(d.amount) AS amount,  y.year
From year_ref y
    Join month_ref m
        On m.year_ref_id = y.id
    Join daily d
        On d.month_ref_id = m.id
Where y.year Between 1980 And 2000
    And m.month = 12
    And m.category_id = '001'
    And d.daily_flag_id <> 'M'
    And exists   (
                Select 1
                From station s1
                    inner Join city c1
                        On c1.id = 10663
                Where 6371.009
                      * SQRT(
                            POW(RADIANS(c1.latitude_decimal - s1.latitude_decimal), 2)
                            + (
                                COS(RADIANS(c1.latitude_decimal + s1.latitude_decimal) / 2)
                                * POW(RADIANS(c1.longitude_decimal - s1.longitude_decimal), 2)
                                )
                            ) <= 50
                    And S1.station_district_id = y.station_district_id
                )
Group By y.year