Re: [Postgres-xc-developers] Replicated update and delete

[Abbas B. <abb...@en...>]

On Thu, Feb 13, 2014 at 9:15 AM, Koichi Suzuki <koi...@gm...>wrote:

> Hi,
>
> I tested the patch and found that primary key is mandatory.   We need
> to modify regression test considerably to give each replicated table
> primary keys.
>
> I think this patch helps but I'm not afraid this is good, especially
> when we try to take XC features back to PG.
>
> Did you post another patch to use all column values if primary key is
> not available?
>
> I think better way is as follows:
>
> 1) If primary key is defined, use it,
> 2) If not, create a primary key as system column, the size should be 64bit.
> 3) If primary key is added to a replicated table, remove system primary
> key.
>
> The value of primary key can be obtained as follows:
>
> 1) add new column to pgxc_class catalog to represent maximum value of
> the system primary key,
> 2) when first "insert" is done to the primary node, system primary key
> value is taken from 1) and 1) is updated.  The value is returned to
> the coordinator to be propagated to other nodes.
> 3) when subsequent "insert" is being done, system primary key value is
> added to the column value.   In this case, each datanode updates 1)
> column value if it is larger than the current maximum value.
>
> 3) is important to change primary node to another.   This is needed to
> carry over the primary node to another.
>

Otherwise the added primary key could be of type serial, with default
nextval('sequence_type') right?


>
> ALTER TABLE should take care of them.
>
> Other issues are:
>
> 4) pg_dump/pg_dumpall should not include this system column value,
> 5) cluster may need to handle this too to repack system primary key
> value (not now but at least in 1.3 or later).
>
> Regards;
> ---
> Koichi Suzuki
>
>
> 2013-11-02 9:26 GMT+09:00 Mason Sharp <ms...@tr...>:
> > Please see attached patch that tries to address the issue of XC using
> CTID
> > for replicated updates and deletes when it is evaluated at a coordinator
> > instead of being pushed down.
> >
> > The problem here is that CTID could be referring to a different tuple
> > altogether on a different data node, which is what happened for one of
> our
> > Postgres-XC support customers, leading to data issues.
> >
> > Instead, the patch looks for a primary key or unique index (with the
> primary
> > key preferred) and uses those values instead of CTID.
> >
> > The patch could be improved further.  Extra parameters are set even if
> not
> > used in the execution of the prepared statement sent down to the data
> nodes.
> >
> > Regards,
> >
> >
> > --
> > Mason Sharp
> >
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> > Distributed and Clustered Database Solutions
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