Re: Optimizer Path Candidates difference in 9.1.3 and 9.2 beta1

> [ 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.

267 >---/*268 >--- * Loop to check proposed new path against old paths. Note it is possible269 >--- * for more than one old path to be tossed out because new_path dominates270 >--- * it.271 >--- *272 >--- * We can't use foreach here because the loop body may delete the current273 >--- * list cell.274 >--- */275 >---p1_prev = NULL;276 >---for (p1 = list_head(parent_rel->pathlist); p1 != NULL; p1 = p1_next)277 >---{ ...................................338339 >--->---/* 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 RegardsHuang Qi VictorComputer Science of National University of Singapore