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

[Mason S. <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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