From: Chris Browne <cbbrowne@acm.org>
To: pgsql-performance@postgresql.org
Subject: Re: large dataset with write vs read clients
Date: Tue, 12 Oct 2010 12:41:17 -0400
Message-ID: <87aamj9xea.fsf@cbbrowne.afilias-int.info> (raw)
References: <AANLkTimNJc=0ffgRO_gO6Vsq06=aqBYXZouhbv0kBe-i@mail.gmail.com>
<4CAE3FDB.1040909@2ndquadrant.com>
<87ocb3yu10.fsf@mid.deneb.enyo.de>
<4CB0E006.8010905@vmsinfo.com>
mladen.gogala@vmsinfo.com (Mladen Gogala) writes:
> I have a logical problem with asynchronous commit. The "commit"
> command should instruct the database to make the outcome of the
> transaction permanent. The application should wait to see whether the
> commit was successful or not. Asynchronous behavior in the commit
> statement breaks the ACID rules and should not be used in a RDBMS
> system. If you don't need ACID, you may not need RDBMS at all. You may
> try with MongoDB. MongoDB is web scale:
> http://www.youtube.com/watch?v=b2F-DItXtZs
The "client" always has the option of connecting to a set of databases,
and stowing parts of the data hither and thither. That often leads to
the relaxation called "BASE." (And IBM has been selling that relaxation
as MQ-Series since the early '90s!)
There often *ARE* cases where it is acceptable for some of the data to
not be as durable, because that data is readily reconstructed. This is
particularly common for calculated/cached/aggregated data.
Many things can get relaxed for a "data warehouse" data store, where the
database is not authoritative, but rather aggregates data drawn from
other authoritative sources. In such applications, neither the A, C, I,
nor the D are pointedly crucial, in the DW data store.
- We don't put the original foreign key constraints into the DW
database; they don't need to be enforced a second time. Ditto for
constraints of all sorts.
- Batching of the loading of updates is likely to break several of the
letters. And I find it *quite* acceptable to lose "D" if the data may
be safely reloaded into the DW database.
I don't think this is either cavalier nor that it points to "MongoDB is
web scale."
--
"cbbrowne","@","gmail.com"
Rules of the Evil Overlord #181. "I will decree that all hay be
shipped in tightly-packed bales. Any wagonload of loose hay attempting
to pass through a checkpoint will be set on fire."
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: cbbrowne@acm.org
Subject: Re: large dataset with write vs read clients
In-Reply-To: <87aamj9xea.fsf@cbbrowne.afilias-int.info>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox