ST_ClusterDBSCAN()

Datum ST_ClusterDBSCAN ( PG_FUNCTION_ARGS  )

extern

Definition at line 120 of file lwgeom_window.c.

{
        WindowObject win_obj = PG_WINDOW_OBJECT();
        uint32_t row = WinGetCurrentPosition(win_obj);
        uint32_t ngeoms = WinGetPartitionRowCount(win_obj);
        cluster_context* context = fetch_cluster_context(win_obj, ngeoms);
 
        if (row == 0) /* beginning of the partition; do all of the work now */
        {
                uint32_t i;
                uint32_t* result_ids;
                LWGEOM** geoms;
                char* is_in_cluster = NULL;
                UNIONFIND* uf;
                bool tolerance_is_null;
                bool minpoints_is_null;
                Datum tolerance_datum = WinGetFuncArgCurrent(win_obj, 1, &tolerance_is_null);
                Datum minpoints_datum = WinGetFuncArgCurrent(win_obj, 2, &minpoints_is_null);
                double tolerance = DatumGetFloat8(tolerance_datum);
                int minpoints = DatumGetInt32(minpoints_datum);
 
                context->is_error = LW_TRUE; /* until proven otherwise */
 
                /* Validate input parameters */
                if (tolerance_is_null || tolerance < 0)
                {
                        lwpgerror("Tolerance must be a positive number, got %g", tolerance);
                        PG_RETURN_NULL();
                }
                if (minpoints_is_null || minpoints < 0)
                {
                        lwpgerror("Minpoints must be a positive number, got %d", minpoints);
                }
 
                initGEOS(lwpgnotice, lwgeom_geos_error);
                geoms = lwalloc(ngeoms * sizeof(LWGEOM*));
                uf = UF_create(ngeoms);
                for (i = 0; i < ngeoms; i++)
                {
                        bool geom_is_null;
                        geoms[i] = read_lwgeom_from_partition(win_obj, i, &geom_is_null);
                        context->clusters[i].is_null = geom_is_null;
 
                        if (!geoms[i]) {
                                /* TODO release memory ? */
                                lwpgerror("Error reading geometry.");
                                PG_RETURN_NULL();
                        }
                }
 
                if (union_dbscan(geoms, ngeoms, uf, tolerance, minpoints, minpoints > 1 ? &is_in_cluster : NULL) == LW_SUCCESS)
                        context->is_error = LW_FALSE;
 
                for (i = 0; i < ngeoms; i++)
                {
                        lwgeom_free(geoms[i]);
                }
                lwfree(geoms);
 
                if (context->is_error)
                {
                        UF_destroy(uf);
                        if (is_in_cluster)
                                lwfree(is_in_cluster);
                        lwpgerror("Error during clustering");
                        PG_RETURN_NULL();
                }
 
                result_ids = UF_get_collapsed_cluster_ids(uf, is_in_cluster);
                for (i = 0; i < ngeoms; i++)
                {
                        if (minpoints > 1 && !is_in_cluster[i])
                        {
                                context->clusters[i].is_null = LW_TRUE;
                        }
                        else
                        {
                                context->clusters[i].cluster_id = result_ids[i];
                        }
                }
 
                lwfree(result_ids);
                UF_destroy(uf);
        }
 
        if (context->clusters[row].is_null)
                PG_RETURN_NULL();
 
        PG_RETURN_INT32(context->clusters[row].cluster_id);
}

References cluster_entry::cluster_id, cluster_context::clusters, fetch_cluster_context(), cluster_context::is_error, cluster_entry::is_null, LW_FALSE, LW_SUCCESS, LW_TRUE, lwalloc(), lwfree(), lwgeom_free(), lwgeom_geos_error(), read_lwgeom_from_partition(), UF_create(), UF_destroy(), UF_get_collapsed_cluster_ids(), and union_dbscan().

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