Anyone? I'd like some feedback before moving on to do the seq scan + sort in those CLUSTER cases where "use_index_scan" returns false...
----- Messaggio originale ----- > Da: Leonardo F <m_li...@yahoo.it> > A: pgsql-hackers@postgresql.org > Inviato: Mer 20 gennaio 2010, 18:48:00 > Oggetto: Re: [HACKERS] About "Our CLUSTER implementation is pessimal" patch > > > I read the thread "Our CLUSTER implementation is pessimal" > > http://archives.postgresql.org/pgsql-hackers/2008-08/msg01371.php . > > > > I was going to try to add the proper cost_index/cost_sort calls to decide > which > > "path" should be executed, as in: > > > > http://archives.postgresql.org/pgsql-hackers/2008-09/msg00517.php > > I think I got something up and running to check if a table scan + sort is > supposed > to be faster than an index scan for a certain CLUSTER operation. > > The way I did it is (I guess...) wrong: I created the elements needed by > get_relation_info, create_seqscan_path, create_index_path, cost_sort. > > It has been, obviously, a trial and error approach: I added the member values > as > soon as one function call crashed... and I bet I didn't get all the corner > cases. > Is there any better way of doing it? > > Leonardo > > (this is called in copy_heap_data to decide which path to choose:) > > static bool use_index_scan(Oid tableOid, Oid indexOid) > { > RelOptInfo *rel; > PlannerInfo *root; > Query *query; > PlannerGlobal *glob; > Path *seqAndSortPath; > IndexPath *indexPath; > RangeTblEntry *rte; > > rel = makeNode(RelOptInfo); > rel->reloptkind = RELOPT_BASEREL; > rel->relid = 1; > rel->rtekind = RTE_RELATION; > > /* needed by get_relation_info */ > glob = makeNode(PlannerGlobal); > > /* needed by get_relation_info: */ > query = makeNode(Query); > query->resultRelation = 0; > > root = makeNode(PlannerInfo); > > root->parse = query; > root->glob = glob; > > get_relation_info(root, tableOid, false, rel); > seqAndSortPath = create_seqscan_path(NULL, rel); > > rel->rows = rel->tuples; > > rte = makeNode(RangeTblEntry); > rte->rtekind = RTE_RELATION; > rte->relid = tableOid; > > root->simple_rel_array_size = 2; > root->simple_rte_array = (RangeTblEntry **) > palloc0(root->simple_rel_array_size * sizeof(RangeTblEntry *)); > root->simple_rte_array[1] = rte; > > root->total_table_pages = rel->pages; > > indexPath = create_index_path(root, > (IndexOptInfo*)(list_head(rel->indexlist)->data.ptr_value), NULL, NULL, > ForwardScanDirection, NULL); > cost_sort(seqAndSortPath, root, NULL, seqAndSortPath->total_cost, > rel->tuples, > rel->width, -1); > > return indexPath->path.total_cost < seqAndSortPath->total_cost; > } -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
