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

[Javier H. <jhe...@ce...>]

Hi Ashutosh,

The current code (v1.1) is:

         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.
              */
         case T_FieldStore:
             /*
              * PostgreSQL deparsing logic does not handle the FieldStore
              * for more than one fields (see processIndirection()). So, 
let's
              * handle it through standard planner, where whole row will be
              * constructed.
              */
         case T_SetToDefault:
             /*
              * PGXCTODO: we should actually check whether the default 
value to
              * be substituted is shippable to the Datanode. Some cases like
              * nextval() of a sequence can not be shipped to the 
Datanode, hence
              * for now default values can not be shipped to the Datanodes
              */
             pgxc_set_shippability_reason(sc_context, SS_UNSUPPORTED_EXPR);
             pgxc_set_exprtype_shippability(exprType(node), sc_context);
             break;


Sorry, next time I will send a patch.


On 09/10/13 13:24, Ashutosh Bapat wrote:
> 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... 
> <mailto: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
>     Fax:   +34 978 611801
>
>
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>
> -- 
> Best Wishes,
> Ashutosh Bapat
> EnterpriseDB Corporation
> The Postgres Database Company