Question

下面的查询将进行批量选择，然后循环更新记录。我想在这里使用BULK COLLECT INTO和FORALL构造来提高性能。但是查询使用rownum更新循环中的列。无论如何，在获取rownum的同时还能使用BULK COLLECT INTO吗？

     FOR rec IN
        (SELECT rownum rn,
            b.*
        FROM
            (SELECT *
            FROM temp_final a
           WHERE reid  = 1
            AND retype  = 9
            AND sid         = 'r123'
            AND pid = 2191
            ORDER BY a.horder DESC nulls last,
                sname                         ,
                rowgroup                           ,
                dpct DESC nulls last       ,
                name
            ) b
        )
        LOOP
            UPDATE temp_final
            SET horder=rec.rn
             WHERE reid  = 1
            AND retype  = 9
            AND sid         = 'r123'
            AND pid = 2191
            AND mid   =rec.mid;
        END LOOP;

谢谢

Answer 1

您不需要批量收集，您的pl / sql更新尝试执行的操作可以重写为单个MERGE INTO语句，这比使用FORALL效率更高。如果您仍然坚持使用forall，则可以将此MERGE转换为forall块。

MERGE INTO temp_final tgt USING (
    SELECT rowid,
        ROW_NUMBER() OVER(
            ORDER BY
                horder DESC NULLS LAST,sname,rowgroup,dpct DESC NULLS LAST,name
        ) rn
    FROM
        temp_final
    WHERE
        reid = 1
        AND retype = 9
        AND sid = 'r123'
        AND pid = 2191
)
src ON ( tgt.rowid = src.rowid )
WHEN MATCHED THEN UPDATE SET tgt.horder = src.rn;

Answer 2

您可以将rowid与初始选择项一起获取，将批次转储到数组中，然后在FORALL中使用它，例如

declare
  l_num_list sys.odcinumberlist := sys.odcinumberlist();
  l_char_list sys.odcivarchar2list := sys.odcivarchar2list();
begin  
SELECT rownum rn,rowidtochar(rid)
bulk collect into l_num_list, l_char_list
FROM
            (SELECT a.*, rowid rid
            FROM temp_final a
           WHERE reid  = 1
            AND retype  = 9
            AND sid         = 'r123'
            AND pid = 2191
            ORDER BY a.horder DESC nulls last,
                sname                         ,
                rowgroup                           ,
                dpct DESC nulls last       ,
                name
            ) b;

forall i in 1 .. l_num_list.count
            UPDATE temp_final
            SET horder=l_num_list(i)
            WHERE rowid = chartorowid(l_char_list(i));

end;
/

结合使用BULK COLLECT和rownum

2 个答案: