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Commit6c00d2c

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Tidy up join_search_one_level code
The code in join_search_one_level was a bit convoluted. With a casualglance, you might think that other_rels_list was being set to somethingother than joinrels[1] when level == 2, however, joinrels[level - 1] isjoinrels[1] when level == 2, so nothing special needs to happen to setother_rels_list. Let's clean that up to avoid confusing anyone.In passing, we may as well modernize the loop inmake_rels_by_clause_joins() and instead of passing in the ListCell tostart looping from, let's just pass in the index where to start from andmake use of for_each_from(). Ever since1cff1b9, Lists are arraysunder the hood. lnext() and list_head() both seem a little too linked-listlike.Author: Alex Hsieh, David Rowley, Richard GuoReviewed-by: Julien RouhaudDiscussion:https://postgr.es/m/CANWNU8x9P9aCXGF%3DaT-A_8mLTAT0LkcZ_ySYrGbcuHzMQw2-1g%40mail.gmail.com
1 parent81ccbe5 commit6c00d2c

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-37
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‎src/backend/optimizer/path/joinrels.c

Lines changed: 18 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -25,8 +25,8 @@
2525

2626
staticvoidmake_rels_by_clause_joins(PlannerInfo*root,
2727
RelOptInfo*old_rel,
28-
List*other_rels_list,
29-
ListCell*other_rels);
28+
List*other_rels,
29+
intfirst_rel_idx);
3030
staticvoidmake_rels_by_clauseless_joins(PlannerInfo*root,
3131
RelOptInfo*old_rel,
3232
List*other_rels);
@@ -93,6 +93,8 @@ join_search_one_level(PlannerInfo *root, int level)
9393
if (old_rel->joininfo!=NIL||old_rel->has_eclass_joins||
9494
has_join_restriction(root,old_rel))
9595
{
96+
intfirst_rel;
97+
9698
/*
9799
* There are join clauses or join order restrictions relevant to
98100
* this rel, so consider joins between this rel and (only) those
@@ -106,24 +108,12 @@ join_search_one_level(PlannerInfo *root, int level)
106108
* to each initial rel they don't already include but have a join
107109
* clause or restriction with.
108110
*/
109-
List*other_rels_list;
110-
ListCell*other_rels;
111-
112111
if (level==2)/* consider remaining initial rels */
113-
{
114-
other_rels_list=joinrels[level-1];
115-
other_rels=lnext(other_rels_list,r);
116-
}
117-
else/* consider all initial rels */
118-
{
119-
other_rels_list=joinrels[1];
120-
other_rels=list_head(other_rels_list);
121-
}
112+
first_rel=foreach_current_index(r)+1;
113+
else
114+
first_rel=0;
122115

123-
make_rels_by_clause_joins(root,
124-
old_rel,
125-
other_rels_list,
126-
other_rels);
116+
make_rels_by_clause_joins(root,old_rel,joinrels[1],first_rel);
127117
}
128118
else
129119
{
@@ -167,8 +157,7 @@ join_search_one_level(PlannerInfo *root, int level)
167157
foreach(r,joinrels[k])
168158
{
169159
RelOptInfo*old_rel= (RelOptInfo*)lfirst(r);
170-
List*other_rels_list;
171-
ListCell*other_rels;
160+
intfirst_rel;
172161
ListCell*r2;
173162

174163
/*
@@ -180,19 +169,12 @@ join_search_one_level(PlannerInfo *root, int level)
180169
!has_join_restriction(root,old_rel))
181170
continue;
182171

183-
if (k==other_level)
184-
{
185-
/* only consider remaining rels */
186-
other_rels_list=joinrels[k];
187-
other_rels=lnext(other_rels_list,r);
188-
}
172+
if (k==other_level)/* only consider remaining rels */
173+
first_rel=foreach_current_index(r)+1;
189174
else
190-
{
191-
other_rels_list=joinrels[other_level];
192-
other_rels=list_head(other_rels_list);
193-
}
175+
first_rel=0;
194176

195-
for_each_cell(r2,other_rels_list,other_rels)
177+
for_each_from(r2,joinrels[other_level],first_rel)
196178
{
197179
RelOptInfo*new_rel= (RelOptInfo*)lfirst(r2);
198180

@@ -286,22 +268,21 @@ join_search_one_level(PlannerInfo *root, int level)
286268
* automatically ensures that each new joinrel is only added to the list once.
287269
*
288270
* 'old_rel' is the relation entry for the relation to be joined
289-
* 'other_rels_list': a list containing the other
290-
* rels to be considered for joining
291-
* 'other_rels': the first cell to be considered
271+
* 'other_rels': a list containing the other rels to be considered for joining
272+
* 'first_rel_idx': the first rel to be considered in 'other_rels'
292273
*
293274
* Currently, this is only used with initial rels in other_rels, but it
294275
* will work for joining to joinrels too.
295276
*/
296277
staticvoid
297278
make_rels_by_clause_joins(PlannerInfo*root,
298279
RelOptInfo*old_rel,
299-
List*other_rels_list,
300-
ListCell*other_rels)
280+
List*other_rels,
281+
intfirst_rel_idx)
301282
{
302283
ListCell*l;
303284

304-
for_each_cell(l,other_rels_list,other_rels)
285+
for_each_from(l,other_rels,first_rel_idx)
305286
{
306287
RelOptInfo*other_rel= (RelOptInfo*)lfirst(l);
307288

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