Re: [Postgres-xc-developers] hash by UUID

[Mason S. <ma...@st...>]

On Tue, Sep 10, 2013 at 4:20 AM, Ashutosh Bapat <
ash...@en...> wrote:

> Unrelated to your patch, I think, we should now change the way we are
> handling hash distribution. Instead of having switch cases to get the hash
> functions, to decide whether a certain column is distributable, we should
> really be looking up the pg_type catalogs. This has following advantages
> 1. hashing for distribution would be inline with rest of the hashing (hash
> joins for example), in the server
> 2. We don't need to keep adding datatypes to switch cases. Any data type
> with a hash function would be hash-distributable. Only thing is we
> shouldn't allow the hash function of a data type to be changed if there is
> a distributed table based on this hash function.
> 3. Tables can be distributed by user defined types which have hash
> functions.
>
> This was serious flaw in the previous design, which needs to be corrected
> before we can add new types to distribution.
>

I would put other things at a higher priority right now to help increase
the user base rather than redesigning this.  Some past reworking of
portions of the code broke things or disabled optimizations that were
previously working that took a long time before they were working again, so
I think we should be careful before undertaking changes. In particular, if
newly proposed changes increase the diff and complexity for merging with
vanilla PostgreSQL, we should be cautious.

Anyway, this is needed by a StormDB support customer who is using
Postgres-XC (not StormDB). We are hoping to keep them as close to the
REL1_1_STABLE branch as possible.  For 1.0, we have had to maintain a
specially patched version for customers to ensure a stable version and
still merge in important bug fixes.

Regards,

Mason



> Same would, then be applicable for modulo distribution where existence of
> % operator with integer input and integer output can be used.
>
>




>
> On Tue, Sep 10, 2013 at 1:00 PM, Andrei Martsinchyk <
> and...@gm...> wrote:
>
>>  Hello,
>>
>> PostgresXC does not support hash distribution by UUID data type.
>> Attached a small patch that enables the feature.
>>
>> --
>> Andrei Martsinchyk
>>
>> StormDB - http://www.stormdb.com
>> The Database Cloud
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>
>
> --
> Best Wishes,
> Ashutosh Bapat
> EnterpriseDB Corporation
> The Postgres Database Company
>
>
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-- 
Mason Sharp

StormDB - http://www.stormdb.com
The Database Cloud
Postgres-XC Support and Services