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sig 11 in RC3

From: mlw <markw(at)mohawksoft(dot)com>
To: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: sig 11 in RC3
Date: 2002-01-04 13:52:25
Message-ID: 3C35B399.D494D3BA@mohawksoft.com (view raw or flat)
Thread:
Lists: pgsql-hackers
I have a couple functions which form the basis of an aggregate. The purpose of
the aggregate function is to be able to perform a GROUP BY on a one to many
table and produce a summary able where all the "many" integers will be packed
in a single array. If this were a text search query, rather than searching
hundreds of entries in the table, one fetch and possibly a detoast is used. It
is MUCH faster for my purpose.

It is used like this:

create table array_lookup as select id1, int_array_aggregate(id2) from lookup
group by (id1) ;

I have written a good number of functions in PGSQL, I'm not a newbe. Could
someone take a look at it? I don't think I am doing anything that would kill
the back end, so it may be a bug in RC3, I am just pulling my hair out. (FYI,
the one to many table may have thousands of rows for an entry.) One more thing:
I'm not getting any elog messages, so it should not be a memory issue.


>>>>>>>>>>>>>>>>
-- Internal function for the aggregate
-- Is called for each item in an aggregation
create function int_agg_state (int4, int4)
        returns int4
        as 'MODULE_FILENAME','int_agg_state'
        language 'c';

-- Internal function for the aggregate
-- Is called at the end of the aggregation, and returns an array.
create function int_agg_final_array (int4)
        returns int4[]
        as 'MODULE_FILENAME','int_agg_final_array'
        language 'c';

-- The aggration funcion.
-- uses the above functions to create an array of integers from an aggregation.
create aggregate int_array_aggregate
(
        BASETYPE = int4,
        SFUNC = int_agg_state,
        STYPE = int4,
        FINALFUNC = int_agg_final_array,
        INITCOND = 0
);

>>>>>>>>>>>>>>>>
/* This is actually a postgres version of a one dimentional array */
typedef struct agg
{
        ArrayType a;
        int     items; /* Number of items in array */
        int     lower; /* Lower bounds of array, used as max during aggregation
*/
        int4    array[1];
}PGARRAY;

#define TOASTED         1
#define START_NUM       8
#define PGARRAY_SIZE(n) (sizeof(PGARRAY) + ((n-1)*sizeof(int4)))

PGARRAY * GetPGArray(int4 state, int fAdd);
Datum int_agg_state(PG_FUNCTION_ARGS);
Datum int_agg_final_array(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(int_agg_state);
PG_FUNCTION_INFO_V1(int_agg_final_array);

/* Manage the aggregation state of the array */
PGARRAY * GetPGArray(int4 state, int fAdd)
{
        PGARRAY *p = (PGARRAY *) state;
        if(!state)
        {
                /* New array */
                int cb = PGARRAY_SIZE(START_NUM);

                p = (PGARRAY *) palloc(cb);

                if(!p)
                {
                        elog(ERROR,"Integer aggregator, cant allocate
memory\n");
                        return 0;
                }

                p->a.size = cb;
                p->a.ndim= 0;
                p->a.flags = 0;
                p->items = 0;
                p->lower= START_NUM;
                return p;
        }
        else if(fAdd)
        {
                /* Ensure array has space */
                if(p->items >= p->lower)
                {
                        PGARRAY *pn;
                        int n = p->lower + p->lower;
                        int cbNew = PGARRAY_SIZE(n);
                        pn = (PGARRAY *) palloc(cbNew);

                        if(!pn)
                        {
                                elog(ERROR,"Integer aggregator, cant allocate
memory\n");
                        }
                        else
                        {
                                memcpy(pn, p, p->a.size);
                                pn->a.size = cbNew;
                                pn->lower = n;
                                pfree(p);
                                return pn;
                        }
                }
        }
        return p;
}
/* Called for each iteration during an aggregate function */
Datum int_agg_state(PG_FUNCTION_ARGS)
{
        int4 state = PG_GETARG_INT32(0);
        int4 value = PG_GETARG_INT32(1);

        PGARRAY *p = GetPGArray(state, 1);
        if(!p)
        {
                elog(ERROR,"No aggregate storage\n");
        }
        else if(p->items >= p->lower)
        {
                elog(ERROR,"aggregate storage too small\n");
        }
        else
        {
                p->array[p->items++]= value;
        }
        PG_RETURN_INT32(p);
}

/* This is the final function used for the integer aggregator. It returns all
the integers
 * collected as a one dimentional integer array */
Datum int_agg_final_array(PG_FUNCTION_ARGS)
{
        PGARRAY *p = GetPGArray(PG_GETARG_INT32(0),0);

        if(p)
        {
                /* Fix up the fields in the structure, so Postgres understands
*/
                p->a.size = PGARRAY_SIZE(p->items);
                p->a.ndim=1;
                p->a.flags = 0;
                p->lower = 0;
                PG_RETURN_POINTER(p);
        }
        PG_RETURN_NULL();
}

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