diff options
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 127 |
1 files changed, 67 insertions, 60 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 7d44c4dcfa0..1cf73dffff7 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.71 2001/02/03 21:17:52 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.72 2001/03/22 03:59:34 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -33,12 +33,12 @@ int geqo_rels = DEFAULT_GEQO_RELS; static void set_base_rel_pathlists(Query *root); static void set_plain_rel_pathlist(Query *root, RelOptInfo *rel, - RangeTblEntry *rte); + RangeTblEntry *rte); static void set_inherited_rel_pathlist(Query *root, RelOptInfo *rel, - RangeTblEntry *rte, - List *inheritlist); + RangeTblEntry *rte, + List *inheritlist); static RelOptInfo *make_one_rel_by_joins(Query *root, int levels_needed, - List *initial_rels); + List *initial_rels); #ifdef OPTIMIZER_DEBUG static void debug_print_rel(Query *root, RelOptInfo *rel); @@ -94,7 +94,7 @@ set_base_rel_pathlists(Query *root) RangeTblEntry *rte; List *inheritlist; - Assert(length(rel->relids) == 1); /* better be base rel */ + Assert(length(rel->relids) == 1); /* better be base rel */ rti = lfirsti(rel->relids); rte = rt_fetch(rti, root->rtable); @@ -103,24 +103,25 @@ set_base_rel_pathlists(Query *root) /* Subquery --- generate a separate plan for it */ /* - * If there are any restriction clauses that have been attached - * to the subquery relation, consider pushing them down to become - * HAVING quals of the subquery itself. (Not WHERE clauses, since - * they may refer to subquery outputs that are aggregate results. - * But planner.c will transfer them into the subquery's WHERE if - * they do not.) This transformation is useful because it may - * allow us to generate a better plan for the subquery than - * evaluating all the subquery output rows and then filtering - * them. + * If there are any restriction clauses that have been + * attached to the subquery relation, consider pushing them + * down to become HAVING quals of the subquery itself. (Not + * WHERE clauses, since they may refer to subquery outputs + * that are aggregate results. But planner.c will transfer + * them into the subquery's WHERE if they do not.) This + * transformation is useful because it may allow us to + * generate a better plan for the subquery than evaluating all + * the subquery output rows and then filtering them. * - * Currently, we do not push down clauses that contain subselects, - * mainly because I'm not sure it will work correctly (the - * subplan hasn't yet transformed sublinks to subselects). - * Also, if the subquery contains set ops (UNION/INTERSECT/EXCEPT) - * we do not push down any qual clauses, since the planner doesn't - * support quals at the top level of a setop. (With suitable - * analysis we could try to push the quals down into the component - * queries of the setop, but getting it right is not trivial.) + * Currently, we do not push down clauses that contain + * subselects, mainly because I'm not sure it will work + * correctly (the subplan hasn't yet transformed sublinks to + * subselects). Also, if the subquery contains set ops + * (UNION/INTERSECT/EXCEPT) we do not push down any qual + * clauses, since the planner doesn't support quals at the top + * level of a setop. (With suitable analysis we could try to + * push the quals down into the component queries of the + * setop, but getting it right is not trivial.) * Non-pushed-down clauses will get evaluated as qpquals of * the SubqueryScan node. * @@ -136,8 +137,8 @@ set_base_rel_pathlists(Query *root) foreach(lst, rel->baserestrictinfo) { - RestrictInfo *rinfo = (RestrictInfo *) lfirst(lst); - Node *clause = (Node *) rinfo->clause; + RestrictInfo *rinfo = (RestrictInfo *) lfirst(lst); + Node *clause = (Node *) rinfo->clause; if (contain_subplans(clause)) { @@ -146,13 +147,14 @@ set_base_rel_pathlists(Query *root) } else { + /* - * We need to replace Vars in the clause (which must - * refer to outputs of the subquery) with copies of - * the subquery's targetlist expressions. Note that - * at this point, any uplevel Vars in the clause - * should have been replaced with Params, so they - * need no work. + * We need to replace Vars in the clause (which + * must refer to outputs of the subquery) with + * copies of the subquery's targetlist + * expressions. Note that at this point, any + * uplevel Vars in the clause should have been + * replaced with Params, so they need no work. */ clause = ResolveNew(clause, rti, 0, rte->subquery->targetList, @@ -160,11 +162,12 @@ set_base_rel_pathlists(Query *root) rte->subquery->havingQual = make_and_qual(rte->subquery->havingQual, clause); + /* * We need not change the subquery's hasAggs or - * hasSublinks flags, since we can't be pushing down - * any aggregates that weren't there before, and we - * don't push down subselects at all. + * hasSublinks flags, since we can't be pushing + * down any aggregates that weren't there before, + * and we don't push down subselects at all. */ } } @@ -215,9 +218,9 @@ set_plain_rel_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte) /* * Generate paths and add them to the rel's pathlist. * - * Note: add_path() will discard any paths that are dominated by - * another available path, keeping only those paths that are - * superior along at least one dimension of cost or sortedness. + * Note: add_path() will discard any paths that are dominated by another + * available path, keeping only those paths that are superior along at + * least one dimension of cost or sortedness. */ /* Consider sequential scan */ @@ -230,9 +233,9 @@ set_plain_rel_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte) create_index_paths(root, rel, indices); /* - * Note: create_or_index_paths depends on create_index_paths to - * have marked OR restriction clauses with relevant indices; this - * is why it doesn't need to be given the list of indices. + * Note: create_or_index_paths depends on create_index_paths to have + * marked OR restriction clauses with relevant indices; this is why it + * doesn't need to be given the list of indices. */ create_or_index_paths(root, rel, rel->baserestrictinfo); @@ -258,8 +261,8 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte, List *il; /* - * XXX for now, can't handle inherited expansion of FOR UPDATE; - * can we do better? + * XXX for now, can't handle inherited expansion of FOR UPDATE; can we + * do better? */ if (intMember(parentRTindex, root->rowMarks)) elog(ERROR, "SELECT FOR UPDATE is not supported for inherit queries"); @@ -271,14 +274,14 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte, rel->width = 0; /* - * Generate access paths for each table in the tree (parent AND children), - * and pick the cheapest path for each table. + * Generate access paths for each table in the tree (parent AND + * children), and pick the cheapest path for each table. */ foreach(il, inheritlist) { - int childRTindex = lfirsti(il); + int childRTindex = lfirsti(il); RangeTblEntry *childrte; - Oid childOID; + Oid childOID; RelOptInfo *childrel; childrte = rt_fetch(childRTindex, root->rtable); @@ -289,16 +292,18 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte, * attach the RelOptInfo to the query's base_rel_list, however. * * NOTE: when childRTindex == parentRTindex, we create a second - * RelOptInfo for the same relation. This RelOptInfo will represent - * the parent table alone, whereas the original RelOptInfo represents - * the union of the inheritance tree members. + * RelOptInfo for the same relation. This RelOptInfo will + * represent the parent table alone, whereas the original + * RelOptInfo represents the union of the inheritance tree + * members. */ childrel = make_base_rel(root, childRTindex); /* - * Copy the parent's targetlist and restriction quals to the child, - * with attribute-number adjustment if needed. We don't bother - * to copy the join quals, since we can't do any joining here. + * Copy the parent's targetlist and restriction quals to the + * child, with attribute-number adjustment if needed. We don't + * bother to copy the join quals, since we can't do any joining + * here. */ childrel->targetlist = (List *) adjust_inherited_attrs((Node *) rel->targetlist, @@ -328,8 +333,8 @@ set_inherited_rel_pathlist(Query *root, RelOptInfo *rel, RangeTblEntry *rte, } /* - * Finally, build Append path and install it as the only access - * path for the parent rel. + * Finally, build Append path and install it as the only access path + * for the parent rel. */ add_path(rel, (Path *) create_append_path(rel, subpaths)); @@ -350,9 +355,9 @@ make_fromexpr_rel(Query *root, FromExpr *from) List *jt; /* - * Count the number of child jointree nodes. This is the depth - * of the dynamic-programming algorithm we must employ to consider - * all ways of joining the child nodes. + * Count the number of child jointree nodes. This is the depth of the + * dynamic-programming algorithm we must employ to consider all ways + * of joining the child nodes. */ levels_needed = length(from->fromlist); @@ -374,6 +379,7 @@ make_fromexpr_rel(Query *root, FromExpr *from) if (levels_needed == 1) { + /* * Single jointree node, so we're done. */ @@ -381,6 +387,7 @@ make_fromexpr_rel(Query *root, FromExpr *from) } else { + /* * Consider the different orders in which we could join the rels, * using either GEQO or regular optimizer. @@ -401,7 +408,7 @@ make_fromexpr_rel(Query *root, FromExpr *from) * independent jointree items in the query. This is > 1. * * 'initial_rels' is a list of RelOptInfo nodes for each independent - * jointree item. These are the components to be joined together. + * jointree item. These are the components to be joined together. * * Returns the final level of join relations, i.e., the relation that is * the result of joining all the original relations together. @@ -423,8 +430,8 @@ make_one_rel_by_joins(Query *root, int levels_needed, List *initial_rels) * joinitems[j] is a list of all the j-item rels. Initially we set * joinitems[1] to represent all the single-jointree-item relations. */ - joinitems = (List **) palloc((levels_needed+1) * sizeof(List *)); - MemSet(joinitems, 0, (levels_needed+1) * sizeof(List *)); + joinitems = (List **) palloc((levels_needed + 1) * sizeof(List *)); + MemSet(joinitems, 0, (levels_needed + 1) * sizeof(List *)); joinitems[1] = initial_rels; |