RE: Implementing Incremental View Maintenance

Hi Nagata-san,

Sorry for late reply.

> However, even if we create triggers recursively on the parents or children, we would still
> need more consideration. This is because we will have to convert the format of tuple of
> modified table to the format of the table specified in the view for cases that the parent
> and some children have different format.
>
> I think supporting partitioned tables can be left for the next release.

OK. I understand.
In the v24-patch, creating IVM on partions or partition table is prohibited.
It is OK but it should be documented.

Perhaps, the following statement describe this.
If so, I think the definition of "simple base table" is ambiguous for some users.

+ IMMVs must be based on simple base tables. It's not supported to
+ create them on top of views or materialized views.

> DEPENDENCY_IMMV was added to clear that a certain trigger is related to IMMV.
> We dropped the IVM trigger and its dependencies from IMMV when REFRESH ... WITH NO DATA
> is executed. Without the new deptype, we may accidentally delete a dependency created
> with an intention other than the IVM trigger.

OK. I understand.

> I think it is harder than you expected. When an IMMV is switched to a normal
> materialized view, we needs to drop hidden columns (__ivm_count__ etc.), and in
> the opposite case, we need to create them again. The former (IMMV->IVM) might be
> easer, but for the latter (IVM->IMMV) I wonder we would need to re-create
> IMMV.

OK. I understand.

Regards,
Ryohei Takahashi