ST_Subdivide()

Datum ST_Subdivide

(

PG_FUNCTION_ARGS

)

Definition at line 329 of file lwgeom_dump.c.

{
        typedef struct
        {
                int nextgeom;
                int numgeoms;
                LWCOLLECTION *col;
        } collection_fctx;
 
        FuncCallContext *funcctx;
        collection_fctx *fctx;
        MemoryContext oldcontext;
 
        /* stuff done only on the first call of the function */
        if (SRF_IS_FIRSTCALL())
        {
                GSERIALIZED *gser;
                LWGEOM *geom;
                LWCOLLECTION *col;
                /* default to maxvertices < page size */
                int maxvertices = 128;
 
                /* create a function context for cross-call persistence */
                funcctx = SRF_FIRSTCALL_INIT();
 
                /*
                * switch to memory context appropriate for multiple function calls
                */
                oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
                /*
                * Get the geometry value
                */
                gser = PG_GETARG_GSERIALIZED_P(0);
                geom = lwgeom_from_gserialized(gser);
 
                /*
                * Get the max vertices value
                */
                if ( PG_NARGS() > 1 && ! PG_ARGISNULL(1) )
                        maxvertices = PG_GETARG_INT32(1);
 
                /*
                * Compute the subdivision of the geometry
                */
                col = lwgeom_subdivide(geom, maxvertices);
 
                if ( ! col )
                        SRF_RETURN_DONE(funcctx);
 
                /* allocate memory for user context */
                fctx = (collection_fctx *) palloc(sizeof(collection_fctx));
 
                /* initialize state */
                fctx->nextgeom = 0;
                fctx->numgeoms = col->ngeoms;
                fctx->col = col;
 
                /* save user context, switch back to function context */
                funcctx->user_fctx = fctx;
                MemoryContextSwitchTo(oldcontext);
        }
 
        /* stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();
        fctx = funcctx->user_fctx;
 
        if (fctx->nextgeom < fctx->numgeoms)
        {
                GSERIALIZED *gpart = geometry_serialize(fctx->col->geoms[fctx->nextgeom]);
                fctx->nextgeom++;
                SRF_RETURN_NEXT(funcctx, PointerGetDatum(gpart));
        }
        else
        {
                /* do when there is no more left */
                SRF_RETURN_DONE(funcctx);
        }
}

References geometry_serialize(), lwgeom_from_gserialized(), lwgeom_subdivide(), and LWCOLLECTION::ngeoms.

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