Re: Persistence problem - Mailing list pgsql-general

UPDATE:

When I do this:

    realResult = (mPoint *)palloc(result->length);
    memcpy(realResult, result, result->length);

I get a right result in the same session, but corrupted in the next one.
I've also found one place in create_mPoint where I used realloc. But why would it matter if I copied the memory into a new variable?

Ivan

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From: i.bre@live.com
To: kleptog@svana.org
CC: dalroi@solfertje.student.utwente.nl; pgsql-general@postgresql.org
Subject: RE: [GENERAL] Persistence problem
Date: Thu, 13 May 2010 12:04:56 +0200

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I'll try to explain with as less code as possible.
One of the types I wanted to create is called mpoint. This is a part of code:

Datum mpoint_in(PG_FUNCTION_ARGS)
{
    char *str = PG_GETARG_CSTRING(0);
    mPoint *result;

    result = (mPoint *) create_mPoint(str);

    if (result == NULL) {
        Log ("mpoint_in: reporting error for invalid input syntax for mPoint");
        ereport(ERROR, (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION), errmsg("invalid input syntax for mPoint: \"%s\"", str)));
    }
   
    PG_RETURN_POINTER(result);
}

In SQL the internallength for the type is set to VARIABLE. The type mpoint is complex. It is a structure containing other structures.

typedef struct {
    int4 length;
    int noOfUnits;
    void *units; // this is later casted to uPoint *
} mapping_t;

typedef mapping_t    mPoint;

typedef struct {
    timeint_t interval;
    double x1, x0, y1, y0;
} uPoint;

typedef upoint_t    uPoint;

typedef struct {
    time_T start, end;
    short int LC, RC;
} timeint_t;

typedef struct {
    double time;
    short int infinity;
} time_T;

The function create_mPoint (char *str) creates the type. It is pretty complex and I don't think it's smart to post it here. Anyway, it creates dinamycally array of uPoints for units. During that period, I've used palloc. At the end I set the variable length:

result->length = sizeof(int4) + sizeof(int) + result->noOfUnits * sizeof(uPoint);

My first guess was that I don't have all the data directly next to each other in the memory. Then I've tried to add this in the function mpoint_in, after I get the result from create_mPoint:

    mPoint *finalResult;
    finalResult = (mPoint *)palloc(sizeof(mPoint));
    finalResult->units = (uPoint *)palloc(result->noOfUnits * sizeof(uPoint));
    memcpy(finalResult->units, result->units, result->noOfUnits * sizeof(uPoint));
    finalResult->noOfUnits = result->noOfUnits;
    finalResult->length = result->length;
    PG_RETURN_POINTER(finalResult);

When I call ToString (I've made it myself), I get the same content for both result and finalResult. However, unlike the first case when I return result and get normal data in that session which dissapears in next one, this time I get corrupted data even in the first session.

More code? More explanation? Or someone has an idea?

Thank you very much.
Ivan


> Date: Wed, 12 May 2010 19:45:26 +0200
> From: kleptog@svana.org
> To: i.bre@live.com
> CC: dalroi@solfertje.student.utwente.nl; pgsql-general@postgresql.org
> Subject: Re: [GENERAL] Persistence problem
>
> On Wed, May 12, 2010 at 07:12:10PM +0200, I. B. wrote:
> >
> > That was my first guess. I used palloc everywhere.. But to be sure, after I made the type, I tried to do the something like:
> >
> > mytype * result;
> > mytype * realResult;
> > result = createType(...);
> > realResult = (mytype *)palloc(mytype->length);
> > mempcy (realResult, result, result->length);
>
> Did you define the type properly at SQL level? Is it a varlena type or
> fixed length? Did you return it properly (as Datum)?
>
> You're going to need to post more information before we can help you
> usefully.
>
> Have a nice day,
> --
> Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
> > Patriotism is when love of your own people comes first; nationalism,
> > when hate for people other than your own comes first.
> > - Charles de Gaulle

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