Re: Postgres as In-Memory Database?

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
>
>