其代码结构:
/* * build_join_rel * Returns relation entry corresponding to the union of two given rels, * creating a new relation entry if none already exists. * * 'joinrelids' is the Relids set that uniquely identifies the join * 'outer_rel' and 'inner_rel' are relation nodes for the relations to be * joined * 'sjinfo': join context info * 'restrictlist_ptr': result variable. If not NULL, *restrictlist_ptr * receives the list of RestrictInfo nodes that apply to this * particular pair of joinable relations. * * restrictlist_ptr makes the routine's API a little grotty, but it saves * duplicated calculation of the restrictlist... */ RelOptInfo * build_join_rel(PlannerInfo *root, Relids joinrelids, RelOptInfo *outer_rel, RelOptInfo *inner_rel, SpecialJoinInfo *sjinfo, List **restrictlist_ptr) { RelOptInfo *joinrel; List *restrictlist; /* * See if we already have a joinrel for this set of base rels. */ joinrel = find_join_rel(root, joinrelids); if (joinrel) { /* * Yes, so we only need to figure the restrictlist for this particular * pair of component relations. */ if (restrictlist_ptr) *restrictlist_ptr = build_joinrel_restrictlist(root, joinrel, outer_rel, inner_rel); return joinrel; } /* * Nope, so make one. */ joinrel = makeNode(RelOptInfo); joinrel->reloptkind = RELOPT_JOINREL; joinrel->relids = bms_copy(joinrelids); joinrel->rows = 0; joinrel->width = 0; joinrel->reltargetlist = NIL; joinrel->pathlist = NIL; joinrel->ppilist = NIL; joinrel->cheapest_startup_path = NULL; joinrel->cheapest_total_path = NULL; joinrel->cheapest_unique_path = NULL; joinrel->cheapest_parameterized_paths = NIL; joinrel->relid = 0; /* indicates not a baserel */ joinrel->rtekind = RTE_JOIN; joinrel->min_attr = 0; joinrel->max_attr = 0; joinrel->attr_needed = NULL; joinrel->attr_widths = NULL; joinrel->indexlist = NIL; joinrel->pages = 0; joinrel->tuples = 0; joinrel->allvisfrac = 0; joinrel->subplan = NULL; joinrel->subroot = NULL; joinrel->fdwroutine = NULL; joinrel->fdw_private = NULL; joinrel->baserestrictinfo = NIL; joinrel->baserestrictcost.startup = 0; joinrel->baserestrictcost.per_tuple = 0; joinrel->joininfo = NIL; joinrel->has_eclass_joins = false; /* * Create a new tlist containing just the vars that need to be output from * this join (ie, are needed for higher joinclauses or final output). * * NOTE: the tlist order for a join rel will depend on which pair of outer * and inner rels we first try to build it from. But the contents should * be the same regardless. */ build_joinrel_tlist(root, joinrel, outer_rel); build_joinrel_tlist(root, joinrel, inner_rel); add_placeholders_to_joinrel(root, joinrel); /* * Construct restrict and join clause lists for the new joinrel. (The * caller might or might not need the restrictlist, but I need it anyway * for set_joinrel_size_estimates().) */ restrictlist = build_joinrel_restrictlist(root, joinrel, outer_rel, inner_rel); if (restrictlist_ptr) *restrictlist_ptr = restrictlist; build_joinrel_joinlist(joinrel, outer_rel, inner_rel); /* * This is also the right place to check whether the joinrel has any * pending EquivalenceClass joins. */ joinrel->has_eclass_joins = has_relevant_eclass_joinclause(root, joinrel); /* * Set estimates of the joinrel's size. */ set_joinrel_size_estimates(root, joinrel, outer_rel, inner_rel, sjinfo, restrictlist); /* * Add the joinrel to the query's joinrel list, and store it into the * auxiliary hashtable if there is one. NB: GEQO requires us to append * the new joinrel to the end of the list! */ root->join_rel_list = lappend(root->join_rel_list, joinrel); if (root->join_rel_hash) { JoinHashEntry *hentry; bool found; hentry = (JoinHashEntry *) hash_search(root->join_rel_hash, &(joinrel->relids), HASH_ENTER, &found); Assert(!found); hentry->join_rel = joinrel; } /* * Also, if dynamic-programming join search is active, add the new joinrel * to the appropriate sublist. Note: you might think the Assert on number * of members should be for equality, but some of the level 1 rels might * have been joinrels already, so we can only assert <=. */ if (root->join_rel_level) { Assert(root->join_cur_level > 0); Assert(root->join_cur_level <= bms_num_members(joinrel->relids)); root->join_rel_level[root->join_cur_level] = lappend(root->join_rel_level[root->join_cur_level], joinrel); } return joinrel; }
其中:
build_joinrel_tlist: 就是targetlist (table 名集合)
restrictlist: 两个table各自的where条件
build_joinrel_jionlist: jion条件集合
本文转自健哥的数据花园博客园博客,原文链接:http://www.cnblogs.com/gaojian/archive/2013/06/13/3134009.html,如需转载请自行联系原作者