diff options
Diffstat (limited to 'src/backend/optimizer/geqo/geqo_eval.c')
| -rw-r--r-- | src/backend/optimizer/geqo/geqo_eval.c | 91 |
1 files changed, 44 insertions, 47 deletions
diff --git a/src/backend/optimizer/geqo/geqo_eval.c b/src/backend/optimizer/geqo/geqo_eval.c index d1bb3059fc0..0a2dee08dc8 100644 --- a/src/backend/optimizer/geqo/geqo_eval.c +++ b/src/backend/optimizer/geqo/geqo_eval.c @@ -6,7 +6,7 @@ * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_eval.c,v 1.76 2005/06/09 04:18:59 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_eval.c,v 1.77 2005/10/15 02:49:19 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -52,15 +52,15 @@ geqo_eval(Gene *tour, int num_gene, GeqoEvalData *evaldata) struct HTAB *savehash; /* - * Because gimme_tree considers both left- and right-sided trees, - * there is no difference between a tour (a,b,c,d,...) and a tour - * (b,a,c,d,...) --- the same join orders will be considered. To avoid - * redundant cost calculations, we simply reject tours where tour[0] > - * tour[1], assigning them an artificially bad fitness. + * Because gimme_tree considers both left- and right-sided trees, there is + * no difference between a tour (a,b,c,d,...) and a tour (b,a,c,d,...) --- + * the same join orders will be considered. To avoid redundant cost + * calculations, we simply reject tours where tour[0] > tour[1], assigning + * them an artificially bad fitness. * * init_tour() is aware of this rule and so we should never reject a tour - * during the initial filling of the pool. It seems difficult to - * persuade the recombination logic never to break the rule, however. + * during the initial filling of the pool. It seems difficult to persuade + * the recombination logic never to break the rule, however. */ if (num_gene >= 2 && tour[0] > tour[1]) return DBL_MAX; @@ -69,10 +69,10 @@ geqo_eval(Gene *tour, int num_gene, GeqoEvalData *evaldata) * Create a private memory context that will hold all temp storage * allocated inside gimme_tree(). * - * Since geqo_eval() will be called many times, we can't afford to let - * all that memory go unreclaimed until end of statement. Note we - * make the temp context a child of the planner's normal context, so - * that it will be freed even if we abort via ereport(ERROR). + * Since geqo_eval() will be called many times, we can't afford to let all + * that memory go unreclaimed until end of statement. Note we make the + * temp context a child of the planner's normal context, so that it will + * be freed even if we abort via ereport(ERROR). */ mycontext = AllocSetContextCreate(CurrentMemoryContext, "GEQO", @@ -84,15 +84,15 @@ geqo_eval(Gene *tour, int num_gene, GeqoEvalData *evaldata) /* * gimme_tree will add entries to root->join_rel_list, which may or may * not already contain some entries. The newly added entries will be - * recycled by the MemoryContextDelete below, so we must ensure that - * the list is restored to its former state before exiting. We can - * do this by truncating the list to its original length. NOTE this - * assumes that any added entries are appended at the end! + * recycled by the MemoryContextDelete below, so we must ensure that the + * list is restored to its former state before exiting. We can do this by + * truncating the list to its original length. NOTE this assumes that any + * added entries are appended at the end! * - * We also must take care not to mess up the outer join_rel_hash, - * if there is one. We can do this by just temporarily setting the - * link to NULL. (If we are dealing with enough join rels, which we - * very likely are, a new hash table will get built and used locally.) + * We also must take care not to mess up the outer join_rel_hash, if there is + * one. We can do this by just temporarily setting the link to NULL. (If + * we are dealing with enough join rels, which we very likely are, a new + * hash table will get built and used locally.) */ savelength = list_length(evaldata->root->join_rel_list); savehash = evaldata->root->join_rel_hash; @@ -170,23 +170,22 @@ gimme_tree(Gene *tour, int num_gene, GeqoEvalData *evaldata) * Push each relation onto the stack in the specified order. After * pushing each relation, see whether the top two stack entries are * joinable according to the desirable_join() heuristics. If so, join - * them into one stack entry, and try again to combine with the next - * stack entry down (if any). When the stack top is no longer - * joinable, continue to the next input relation. After we have - * pushed the last input relation, the heuristics are disabled and we - * force joining all the remaining stack entries. + * them into one stack entry, and try again to combine with the next stack + * entry down (if any). When the stack top is no longer joinable, + * continue to the next input relation. After we have pushed the last + * input relation, the heuristics are disabled and we force joining all + * the remaining stack entries. * * If desirable_join() always returns true, this produces a straight - * left-to-right join just like the old code. Otherwise we may - * produce a bushy plan or a left/right-sided plan that really - * corresponds to some tour other than the one given. To the extent - * that the heuristics are helpful, however, this will be a better - * plan than the raw tour. + * left-to-right join just like the old code. Otherwise we may produce a + * bushy plan or a left/right-sided plan that really corresponds to some + * tour other than the one given. To the extent that the heuristics are + * helpful, however, this will be a better plan than the raw tour. * - * Also, when a join attempt fails (because of IN-clause constraints), we - * may be able to recover and produce a workable plan, where the old - * code just had to give up. This case acts the same as a false - * result from desirable_join(). + * Also, when a join attempt fails (because of IN-clause constraints), we may + * be able to recover and produce a workable plan, where the old code just + * had to give up. This case acts the same as a false result from + * desirable_join(). */ for (rel_count = 0; rel_count < num_gene; rel_count++) { @@ -199,8 +198,8 @@ gimme_tree(Gene *tour, int num_gene, GeqoEvalData *evaldata) stack_depth++; /* - * While it's feasible, pop the top two stack entries and replace - * with their join. + * While it's feasible, pop the top two stack entries and replace with + * their join. */ while (stack_depth >= 2) { @@ -208,20 +207,18 @@ gimme_tree(Gene *tour, int num_gene, GeqoEvalData *evaldata) RelOptInfo *inner_rel = stack[stack_depth - 1]; /* - * Don't pop if heuristics say not to join now. However, once - * we have exhausted the input, the heuristics can't prevent - * popping. + * Don't pop if heuristics say not to join now. However, once we + * have exhausted the input, the heuristics can't prevent popping. */ if (rel_count < num_gene - 1 && !desirable_join(evaldata->root, outer_rel, inner_rel)) break; /* - * Construct a RelOptInfo representing the join of these two - * input relations. These are always inner joins. Note that - * we expect the joinrel not to exist in root->join_rel_list - * yet, and so the paths constructed for it will only include - * the ones we want. + * Construct a RelOptInfo representing the join of these two input + * relations. These are always inner joins. Note that we expect + * the joinrel not to exist in root->join_rel_list yet, and so the + * paths constructed for it will only include the ones we want. */ joinrel = make_join_rel(evaldata->root, outer_rel, inner_rel, JOIN_INNER); @@ -266,9 +263,9 @@ desirable_join(PlannerInfo *root, return true; /* - * Join if the rels are members of the same IN sub-select. This is - * needed to improve the odds that we will find a valid solution in a - * case where an IN sub-select has a clauseless join. + * Join if the rels are members of the same IN sub-select. This is needed + * to improve the odds that we will find a valid solution in a case where + * an IN sub-select has a clauseless join. */ foreach(l, root->in_info_list) { |