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Tidy up join_search_one_level code 

The code in join_search_one_level was a bit convoluted.  With a casual
glance, you might think that other_rels_list was being set to something
other than joinrels[1] when level == 2, however, joinrels[level - 1] is
joinrels[1] when level == 2, so nothing special needs to happen to set
other_rels_list.  Let's clean that up to avoid confusing anyone.

In passing, we may as well modernize the loop in
make_rels_by_clause_joins() and instead of passing in the ListCell to
start looping from, let's just pass in the index where to start from and
make use of for_each_from().  Ever since 1cff1b95a, Lists are arrays
under the hood. lnext() and list_head() both seem a little too linked-list
like.

Author: Alex Hsieh, David Rowley, Richard Guo
Reviewed-by: Julien Rouhaud
Discussion: https://postgr.es/m/CANWNU8x9P9aCXGF%3DaT-A_8mLTAT0LkcZ_ySYrGbcuHzMQw2-1g%40mail.gmail.com
This commit is contained in:
David Rowley 2023-08-06 21:51:54 +12:00
parent 81ccbe520f
commit 6c00d2c9d4
1 changed files with 18 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

55
src/backend/optimizer/path/joinrels.c
View File

@ -25,8 +25,8 @@
static void make_rels_by_clause_joins(PlannerInfo *root,
RelOptInfo *old_rel,
List *other_rels_list,
ListCell *other_rels);
List *other_rels,
int first_rel_idx);
static void make_rels_by_clauseless_joins(PlannerInfo *root,
RelOptInfo *old_rel,
List *other_rels);
@ -93,6 +93,8 @@ join_search_one_level(PlannerInfo *root, int level)
if (old_rel->joininfo != NIL || old_rel->has_eclass_joins ||
has_join_restriction(root, old_rel))
{
int first_rel;
/*
* There are join clauses or join order restrictions relevant to
* this rel, so consider joins between this rel and (only) those
@ -106,24 +108,12 @@ join_search_one_level(PlannerInfo *root, int level)
* to each initial rel they don't already include but have a join
* clause or restriction with.
*/
List *other_rels_list;
ListCell *other_rels;
if (level == 2) /* consider remaining initial rels */
{
other_rels_list = joinrels[level - 1];
other_rels = lnext(other_rels_list, r);
}
else /* consider all initial rels */
{
other_rels_list = joinrels[1];
other_rels = list_head(other_rels_list);
}
first_rel = foreach_current_index(r) + 1;
else
first_rel = 0;
make_rels_by_clause_joins(root,
old_rel,
other_rels_list,
other_rels);
make_rels_by_clause_joins(root, old_rel, joinrels[1], first_rel);
}
else
{
@ -167,8 +157,7 @@ join_search_one_level(PlannerInfo *root, int level)
foreach(r, joinrels[k])
{
RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
List *other_rels_list;
ListCell *other_rels;
int first_rel;
ListCell *r2;
/*
@ -180,19 +169,12 @@ join_search_one_level(PlannerInfo *root, int level)
!has_join_restriction(root, old_rel))
continue;
if (k == other_level)
{
/* only consider remaining rels */
other_rels_list = joinrels[k];
other_rels = lnext(other_rels_list, r);
}
if (k == other_level) /* only consider remaining rels */
first_rel = foreach_current_index(r) + 1;
else
{
other_rels_list = joinrels[other_level];
other_rels = list_head(other_rels_list);
}
first_rel = 0;
for_each_cell(r2, other_rels_list, other_rels)
for_each_from(r2, joinrels[other_level], first_rel)
{
RelOptInfo *new_rel = (RelOptInfo *) lfirst(r2);
@ -286,9 +268,8 @@ join_search_one_level(PlannerInfo *root, int level)
* automatically ensures that each new joinrel is only added to the list once.
*
* 'old_rel' is the relation entry for the relation to be joined
* 'other_rels_list': a list containing the other
* rels to be considered for joining
* 'other_rels': the first cell to be considered
* 'other_rels': a list containing the other rels to be considered for joining
* 'first_rel_idx': the first rel to be considered in 'other_rels'
*
* Currently, this is only used with initial rels in other_rels, but it
* will work for joining to joinrels too.
@ -296,12 +277,12 @@ join_search_one_level(PlannerInfo *root, int level)
static void
make_rels_by_clause_joins(PlannerInfo *root,
RelOptInfo *old_rel,
List *other_rels_list,
ListCell *other_rels)
List *other_rels,
int first_rel_idx)
{
ListCell *l;
for_each_cell(l, other_rels_list, other_rels)
for_each_from(l, other_rels, first_rel_idx)
{
RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);