Re: [Postgres-xc-developers] Patch for pg_catalog-based views and pgadmin

[Koichi S. <koi...@gm...>]

Hi Mason-san;

Thanks a lot for the work.  I'd like to summarize what we can and what
we cannot with PG-XC and pgadmin.
----------
Koichi Suzuki



2010/5/13 Mason Sharp <mas...@en...>:
> Pavan Deolasee wrote:
>>
>>
>> On Wed, May 12, 2010 at 3:19 AM, Mason Sharp
>> <mas...@en... <mailto:mas...@en...>>
>> wrote:
>>
>>     I started the task to recognize more "Postgres-XC safe" queries.
>>
>>     I initially focused on native pg_catalog based views like
>>     pg_settings. This is because it used by pgadmin. With the attached
>>     patch, pgadmin no longer complains about such queries because they
>>     are now supported.
>>
>>     The PostgreSQL query rewriter appears to convert the view into a
>>     subquery. I modified the XC planner to check for pg_catalog table
>>     usage in the FROM clause (and subqueries thereof).
>>
>>
>> FWIW here are couple of things that I noticed:
>>
>> +   foreach(item, rtable)
>> +   {
>> +       RangeTblEntry *rte = (RangeTblEntry *) lfirst(item);
>> +
>> +       if (rte->rtekind == RTE_RELATION)
>> +       {
>> +           if (rte->relid > FirstNormalObjectId)
>> +               return false;
>> +       } else if (rte->rtekind == RTE_SUBQUERY)
>> +           return contains_only_pg_catalog (rte->subquery->rtable);
>> +   }
>>
>> This code will break out of the loop if the subquery contains only
>> pg_catalog tables. But other rtable entries may contain reference to
>> non-system tables.
>>
>> The other thing I am worried about is whether its safe to just rely on
>> FirstNormalObjectId to decide if a relation belongs to pg_catalog or
>> not. A user can create a table in pg_catalog (though I think it
>> requires changes to GUC) and that may get an OID larger than the
>> FirstNormalObjectId or we may add a new default schema and create
>> tables in the schema as part of initdb (we do that routinely in EDBAS
>> for example). Should we just explicitly lookup the namespace of the
>> relation instead ?
>>
> Thanks, I made those changes and committed.
>
> Mason
>
>> Thanks,
>> Pavan
>>
>> --
>> Pavan Deolasee
>> EnterpriseDB     http://www.enterprisedb.com
>
>
> --
> Mason Sharp
> EnterpriseDB Corporation
> The Enterprise Postgres Company
>
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