Re: Pluggable Storage - Andres's take

On Fri, Sep 21, 2018 at 5:40 PM Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>
wrote:

>
> On Fri, Sep 21, 2018 at 5:05 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
>
>> Hi,
>>
>> On 2018-09-21 16:57:43 +1000, Haribabu Kommi wrote:
>>
>> > For example, in the sequential scan, the heap returns the slot with
>> > the tuple or with value array of all the columns and then the data gets
>> > filtered and later removed the unnecessary columns with projection.
>> > This works fine for the row based storage. For columnar storage, if
>> > the storage knows that upper layers needs only particular columns,
>> > then they can directly return the specified columns and there is no
>> > need of projection step. This will help the columnar storage also
>> > to return proper columns in a faster way.
>>
>> I think this is an important feature, but I feel fairly strongly that we
>> should only tackle it in a second version. This patchset is already
>> pretty darn large. It's imo not just helpful for columnar, but even for
>> heap - we e.g. spend a lot of time deforming columns that are never
>> accessed. That's particularly harmful when the leading columns are all
>> NOT NULL and fixed width, but even if not, it's painful.
>>
>
> OK. Thanks for your opinion.
> Then I will first try to cleanup the open items of the existing patch.
>

Here I attached further cleanup patches.
1. Re-arrange the GUC variable
2. Added a check function hook for default_table_access_method GUC
3. Added a new hook validate_index. I tried to change the function
validate_index_heapscan to slotify, but that have many problems as it
is accessing some internals of the heapscandesc structure and accessing
the buffer and etc.

So I added a new hook and provided a callback to handle the index insert.
Please check and let me know comments?

I will further add the new API's that are discussed for Zheap storage and
share the patch.

Regards,
Haribabu Kommi
Fujitsu Australia