Re: Postgres as In-Memory Database?

Hi,

I wrote
> Finally the paper is mostly about column stores - nothing about
persistence.

Regarding column store, Hadi wrote 2014-04-03 18:43 GMT+02:00 about the
release of a PostgreSQL Columnar Store called "cstore_fdw" [1]!

@Hadi: Can you say something about usage of cstore FDW in-memory?

Regards, S.

[1] http://citusdata.com/blog/76-postgresql-columnar-store-for-analytics

2014-04-02 0:32 GMT+02:00 Stefan Keller <sfkeller(at)gmail(dot)com>:

> Hi Yeb
>
> Thanks for the pointers.
>
> Of course disk access is not obsolete: As I said, I suppose changes are
> streamed to disk.
>
> When I mentioned "no disk access" I meant the indices of RDBMS which
> designed to handle disk access - which seems to me different in in-memory
> dabases.
>
> The paper referred by you is coming from SAP's chief scientist and it
> confirms actually my claim, that there's no need for a primary index since
> the primary attribute (i.e. all attributes) is already kept sorted
> in-memory.
>
> It also mentions an insert-only technique: "This approach has been adopted
> before in POSTGRES [21] in 1987 and was called "time-travel".
> I would be interested what "time-travel" is and if this is still used by
> Postgres.
> Finally the paper is mostly about column stores - nothing about
> persistence. In mentions Disaster recovery" in the last section about
> future work, though.
>
> -S.
>
>
>
>
> 2014-04-01 21:57 GMT+02:00 Yeb Havinga <yebhavinga(at)gmail(dot)com>:
>
> On 2014-04-01 04:20, Jeff Janes wrote:
>>
>> On Sunday, March 30, 2014, Stefan Keller <sfkeller(at)gmail(dot)com> wrote:
>>
>>> Hi Jeff
>>>
>>> 2013/11/20 Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
>>>
>>>>
>>>> I don't know what you mean about enhancements in the buffer pool.
>>>> For an in-memory database, there shouldn't be a buffer pool in the first
>>>> place, as it is *all* in memory.
>>>>
>>>
>>> You are right: In-memory DBs are making buffer-pooling obsolete -
>>> except for making data persistent (see below).
>>>
>>
>>
>> I would be very reluctant to use any database engine which considered
>> disk access obsolete.
>>
>>
>> The disk is not obsolete but something called 'anti-caching' is used:
>> http://www.vldb.org/pvldb/vol6/p1942-debrabant.pdf
>>
>>
>>
>>
>> Are there any show cases out there?
>>>
>>
>> What did the HANA users have to say? Seems like they would be in the
>> best position to provide the test cases.
>>
>>
>> This paper provides some insights into the research behind HANA
>> http://www.sigmod09.org/images/sigmod1ktp-plattner.pdf
>>
>> regards
>> Yeb
>>
>>
>