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Re: Some new SPI functions

From: "Thomas Hallgren" <thhal(at)mailblocks(dot)com>
To: "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Some new SPI functions
Date: 2004-02-15 00:11:27
Message-ID: 002201c3f358$41d0a410$6601a8c0@ad.eoncompany.com (view raw or flat)
Thread:
Lists: pgsql-patches
Sure, I'll provide some docs. Just wasn't aware that "patchers" did that.

- thomas

----- Original Message ----- 
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>
Sent: Friday, February 13, 2004 06:12
Subject: Re: [PATCHES] Some new SPI functions


>
> 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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