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Re: Some new SPI functions

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Thomas Hallgren <thhal(at)mailblocks(dot)com>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: Some new SPI functions
Date: 2004-02-13 05:12:08
Message-ID: 200402130512.i1D5C8P18240@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-patches
Thomas, if this is ready for application, would you make some SGML
changes to match, or give me text to add for them.  Thanks.

---------------------------------------------------------------------------

Thomas Hallgren wrote:
> I need three new functions in the Server Programming Interface (SPI) when
> mapping an ExecutionPlan to a Java prepared statement (Pl/Java project).
> 
> 
> The execute method of the prepared statement needs to know if the result is
> a ResultSet (SPI_cursor_open) or just a number indicated how many rows that
> where affected (SPI_execp). Currently there's no way I can tell by just
> looking at the plan unless I violate the data hiding and use spi_priv.h. I
> really don't want to do that. Hence the need for SPI_is_cursor_plan
> 
> I send an array of java objects for the arguments. The
> SPI_cursor_open/SPI_execp of course expects the arguments to be Datum's and
> the mapper must convert java objects. The mapping code is based on Oid's so
> I need a way to extract the number of expected arguments and the typeid of
> each arguments.
> 
> I find it likely that other pl<lang> implementations where similar support
> is planned might find these functions useful.
> 
> 
> Thomas Hallgren
> 
> Index: src/backend/executor/spi.c
> ===================================================================
> retrieving revision 1.109
> diff -u -r1.109 spi.c
> --- src/backend/executor/spi.c 2 Dec 2003 19:26:47 -0000 1.109
> +++ src/backend/executor/spi.c 12 Feb 2004 11:13:11 -0000
> @@ -918,6 +918,65 @@
>   PortalDrop(portal, false);
>  }
> 
> +/*
> + * Returns the Oid representing the type id for argument at argIndex. First
> + * parameter is at index zero.
> + */
> +Oid
> +SPI_getargtypeid(void *plan, int argIndex)
> +{
> + if (plan == NULL || argIndex < 0 || argIndex >= ((_SPI_plan*)plan)->nargs)
> + {
> +  SPI_result = SPI_ERROR_ARGUMENT;
> +  return InvalidOid;
> + }
> + return ((_SPI_plan *) plan)->argtypes[argIndex];
> +}
> +
> +/*
> + * Returns the number of arguments for the prepared plan.
> + */
> +int
> +SPI_getargcount(void *plan)
> +{
> + if (plan == NULL)
> + {
> +  SPI_result = SPI_ERROR_ARGUMENT;
> +  return -1;
> + }
> + return ((_SPI_plan *) plan)->nargs;
> +}
> +
> +/*
> + * Returns true if the plan contains exactly one command
> + * and that command originates from normal SELECT (i.e.
> + * *not* a SELECT ... INTO). In essence, the result indicates
> + * if the command can be used with SPI_cursor_open
> + *
> + * Parameters
> + *    plan A plan previously prepared using SPI_prepare
> + */
> +bool
> +SPI_is_cursor_plan(void *plan)
> +{
> + List *qtlist;
> + _SPI_plan *spiplan = (_SPI_plan *) plan;
> + if (spiplan == NULL)
> + {
> +  SPI_result = SPI_ERROR_ARGUMENT;
> +  return false;
> + }
> +
> + qtlist = spiplan->qtlist;
> + if(length(spiplan->ptlist) == 1 && length(qtlist) == 1)
> + {
> +  Query *queryTree = (Query *) lfirst((List *) lfirst(qtlist));
> +  if(queryTree->commandType == CMD_SELECT && queryTree->into == NULL)
> +   return true;
> + }
> + return false;
> +}
> +
>  /* =================== private functions =================== */
> 
>  /*
> Index: src/include/executor/spi.h
> ===================================================================
> retrieving revision 1.41
> diff -u -r1.41 spi.h
> --- src/include/executor/spi.h 2 Dec 2003 19:26:47 -0000 1.41
> +++ src/include/executor/spi.h 12 Feb 2004 11:13:21 -0000
> @@ -90,6 +90,10 @@
>  extern void *SPI_saveplan(void *plan);
>  extern int SPI_freeplan(void *plan);
> 
> +extern Oid SPI_getargtypeid(void *plan, int argIndex);
> +extern int SPI_getargcount(void *plan);
> +extern bool SPI_is_cursor_plan(void *plan);
> +
>  extern HeapTuple SPI_copytuple(HeapTuple tuple);
>  extern TupleDesc SPI_copytupledesc(TupleDesc tupdesc);
>  extern TupleTableSlot *SPI_copytupleintoslot(HeapTuple tuple,
> 
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 8: explain analyze is your friend
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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