具有CASE WHEN EXISTS子查询优化的Oracle SQL查询

我正在使用以下查询在Oracle 11g（11.2.0.3.0）中创建视图。

CREATE OR REPLACE FORCE VIEW V_DOCUMENTS_LIST
(
   ID_DOC,
   ATTACHMENTS_COUNT,
   TOTAL_DIMENSION,
   INSERT_DATE,
   ID_STATE,
   STATE,
   ID_INSTITUTE,
   INSTITUTE,
   HASJOB
)
AS
    SELECT D.ID_DOC,
        COUNT (F.ID_FILE) AS ATTACHMENTS_COUNT,
        CASE
           WHEN SUM (F.DIMENSION) IS NULL THEN 0
           ELSE SUM (F.DIMENSION)
        END
           AS TOTAL_DIMENSION,
        D.INSERT_DATE,
        D.ID_STATE,
        S.STATE_DESC AS STATE,
        D.ID_INSTITUTE,
        E.NAME AS INSTITUTE,
        CASE
           WHEN EXISTS (SELECT D.ID_DOC FROM JOB) THEN 'true'
           ELSE 'false'
        END
           AS HASJOB
    FROM DOCUMENTS D
        LEFT JOIN FILES F ON D.ID_DOC = F.ID_DOC
        JOIN STATES S ON D.ID_STATE = S.ID_STATE
        JOIN INSTITUTES E ON D.ID_INSTITUTE = E.ID_INSTITUTE
    GROUP BY D.ID_DOC,
        D.INSERT_DATE,
        D.ID_STATE,
        S.STATE_DESC,
        D.ID_INSTITUTE,
        E.NAME;

然后我查询这种观点得到值一DataGridView中的ASPX网页。

SELECT * 
FROM V_DOCUMENTS_LIST
ORDER BY ID_STATE DESC, INSTITUTE, INSERT_DATE DESC;

相关表和关系

文件；文件；职位;

文件（1-1）<---->（0-N）个文件

职位（0-1）<---->（0-N）文档

查询视图时，我获得了包含所有相关信息（ID，描述，日期，状态等）以及每个文档的完整文档列表：

• 附件总数;
• 附件的总尺寸（字节） ;
• 布尔值，指示是否有至少一个 JOB 关联到 DOCUMENT 或没有。

一切正常，直到视图包含数千条记录为止。现在，记录量正在增加，并且SELECT * FROM视图上需要大约2:30分钟，具有15.000-20.000条记录。我知道嵌套是我视图中真正耗时的部分SELECT：

CASE
    WHEN EXISTS (SELECT D.ID_DOC FROM JOB) THEN 'true'
    ELSE 'false'
END
AS HASJOB

如何优化视图？