Re: Optimizer Path Candidates difference in 9.1.3 and 9.2 beta1
| От | Qi Huang |
|---|---|
| Тема | Re: Optimizer Path Candidates difference in 9.1.3 and 9.2 beta1 |
| Дата | |
| Msg-id | BAY159-W7DF22CB45893B9D3164B9A3E70@phx.gbl обсуждение исходный текст |
| Ответ на | Re: Optimizer Path Candidates difference in 9.1.3 and 9.2 beta1 (Tom Lane <tgl@sss.pgh.pa.us>) |
| Список | pgsql-hackers |
> [ shrug... ] When you're not showing us exactly what you did, it's hard
> to answer that for sure. But there is some prefiltering logic in
> joinpath.c that you might have to lobotomize too if you want to keep
> known-inferior join paths.
>
> regards, tom lane
Thanks, Tom.
Below is what I did for the code in add_path(). I commented out the section of remove_old, and also make sure always accept_new. Then at make_one_rel(), after calling "rel = make_rel_from_joinlist(root, joinlist); ", I set "pprint(rel)" in the next line. Checking the RelOptInfo printed out in logfile, I can see some bushy trees, in 9.1.3.
Best Regards
267 >---/*
268 >--- * Loop to check proposed new path against old paths. Note it is possible
269 >--- * for more than one old path to be tossed out because new_path dominates
270 >--- * it.
271 >--- *
272 >--- * We can't use foreach here because the loop body may delete the current
273 >--- * list cell.
274 >--- */
275 >---p1_prev = NULL;
276 >---for (p1 = list_head(parent_rel->pathlist); p1 != NULL; p1 = p1_next)
277 >---{
...................................
338
339 >--->---/*
340 >--->--- * Remove current element from pathlist if dominated by new.
341 >--->--- */
342 //>->---if (remove_old)
343 //>->---{
344 //>->--->---parent_rel->pathlist = list_delete_cell(parent_rel->pathlist,
345 //>->--->--->--->--->--->--->--->--->--->--->--->---p1, p1_prev);
346
347 >--->--->---/*
348 >--->--->--- * Delete the data pointed-to by the deleted cell, if possible
349 >--->--->--- */
350 //>->--->---if (!IsA(old_path, IndexPath))
351 //>->--->--->---pfree(old_path);
352 >--->--->---/* p1_prev does not advance */
353 //>->---}
354 //>->---else
355 //>->---{
356 >--->--->---/* new belongs after this old path if it has cost >= old's */
357 >--->--->---if (costcmp >= 0)
358 >--->--->--->---insert_after = p1;
359 >--->--->---/* p1_prev advances */
360 >--->--->---p1_prev = p1;
361 //>->---}
362
363 >--->---/*
364 >--->--- * If we found an old path that dominates new_path, we can quit
365 >--->--- * scanning the pathlist; we will not add new_path, and we assume
366 >--->--- * new_path cannot dominate any other elements of the pathlist.
367 >--->--- */
368 >--->---if (!accept_new)
369 >--->--->---break;
370 >---}
371
372 //>-if (accept_new)
373 //>-{
374 >--->---/* Accept the new path: insert it at proper place in pathlist */
375 >--->---if (insert_after)
376 >--->--->---lappend_cell(parent_rel->pathlist, insert_after, new_path);
377 >--->---else
378 >--->--->---parent_rel->pathlist = lcons(new_path, parent_rel->pathlist);
379 //>-}
380 //>-else
381 //>-{
382 >--->---/* Reject and recycle the new path */
383 //>->---if (!IsA(new_path, IndexPath))
384 //>->--->---pfree(new_path);
385 //>-}
Best Regards
Huang Qi Victor
Computer Science of National University of Singapore
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