Re: [Postgres-xc-general] Feature request - Fast Query Shipping for Select with array element access

[Ashutosh B. <ash...@en...>]

Hi Javier,
What's your change? Can you please provide a patch?


On Wed, Oct 9, 2013 at 4:53 PM, Javier Hernandez <jhe...@ce...>wrote:

>  Hello,
>
>     I am not sure if this is the right mailing list for sending Feature
> request, if not, sorry for the inconvenience.
>
>     I know you are working on improvements to the planner (Feature Request
> #95). One important for my project is the ability to use FQS for queries
> that reference elements in an array column. One example:
>
>     CREATE TABLE TestArray (id SERIAL, flux FLOAT4*[]*, error FLOAT*[]*);
>
>     SELECT flux, error FROM TestArray WHERE id = 12; -- Planner uses FQS
>     SELECT flux[1], error[1] FROM TestArray WHERE id = 12; -- Planner uses
> Remote query and completes in coordinator
>
>     I am beginning to dig in the code and I think I have a temporary
> solution:
>
>
> src/backend/optimizer/util/pgxcship.c:709
>
>         case T_ArrayRef:
>             /*
>              * When multiple values of of an array are updated at once
>              * FQS planner cannot yet handle SQL representation correctly.
>              * So disable FQS in this case and let standard planner manage
> it.
>              */
>             if (sc_context->sc_query != NULL &&
> sc_context->sc_query->commandType == CMD_SELECT) {
>                     pgxc_set_exprtype_shippability(exprType(node),
> sc_context);
>             } else {
>                     pgxc_set_shippability_reason(sc_context,
> SS_UNSUPPORTED_EXPR);
>                     pgxc_set_exprtype_shippability(exprType(node),
> sc_context);
>             }
>             break;
>
>
>     The original code is always marking the query as SS_UNSUPPORTED_EXPR,
> but according to the existing comment I think my change is safe for Select.
> Isn't it?
>
>
> Thank you very much,
>
> --
> Javier Hernández
> Ingeniero de Bases de Datos
> Centro de Estudios de Fisica del Cosmos de Aragon (ceFca)http://www.cefca.es
> Plza San Juan Nº 1, Planta 2ª
> E-44001 Teruel (Spain)
> Phone: +34 978 221266 Ext.1105
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>
>
>
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-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company