Oracle：为什么并行删除不并行？
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Oracle: why parallel delete doesn't go parallel?
提问by Revious
I've tried the following statement. But it doesn't proceed parallel. Why? How can I speed up the operation?
我已经尝试了以下语句。但它不会并行进行。为什么？如何加快操作速度？
ALTER SESSION ENABLE PARALLEL DML;
DELETE /*+ parallel(20) */
FROM table
WHERE flag != 'N';
回答by wanana
try
尝试
ALTER SESSION ENABLE PARALLEL DML;
DELETE /*+ parallel(table, 20) */
FROM table
WHERE flag!= 'N';
you can also try another option to delete data, using CTAS, reference from asktom Deleting many rows from a big table
您还可以尝试另一种删除数据的选项，使用 CTAS，参考来自 asktom Deleting many rows from a big table
create table new_table unrecoverable as select * from old_table where ....;
drop table old_table;
rename new_table to old_table;
create index old_table_idx1 on old_table(c1,c2) unrecoverable parallel 5;
create table new_table unrecoverable as select * from old_table where ....;
删除表 old_table；
将 new_table 重命名为 old_table；
在 old_table(c1,c2) 不可恢复的并行 5 上创建索引 old_table_idx1；
