On 10/25/15 3:37 AM, peon ma wrote:
> Hello
>
> I have a problem with table reflection under multi-thread without lock.
> It works fine under single-thread or multi thread with lock protection.
>
> I got following result by the attached test script:
> single-thread or multi thread with lock protection:
> It prints some logs of create connection, query metadata etc, and
> then the table reflection returned.
> multi-thread without lock protection:
> table reflection returned before create connection and query
> metadata, without any exceptions, loggings, but got empty columns list
> and after about 20ms(metadata of this table fetched), all threads
> works fine(got correct columns list)
>
>
> I did found any related documentation about this, so I want to know:
> Is it a bug?
no
> Or the reflection isn't thread-safe,
it's not for a single MetaData object because the reflection process is
modifying the MetaData object and the Table objects within it
if so, is it thread-safe for
> reflection different tables?
only if those tables have no foreign key dependencies between them. If
you reflect a table A which has a ForeignKeyConstraint to a table B, the
reflection of table B will occur automatically.
(see following code for example)
> |
> withtbl1_lock:
> Table("table1",...)
>
> withtbl2_lock:
> Table("table2",...)
> |
>
>
> Thanks in advance
>
>
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