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Use list_copy_head() instead of list_truncate(list_copy(...), ...)

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Truncating off the end of a freshly copied List is not a very efficient
way of copying the first N elements of a List.

In many of the cases that are updated here, the pattern was only being
used to remove the final element of a List.  That's about the best case
for it, but there were many instances where the truncate trimming the List
down much further.

4cc832f94 added list_copy_head(), so let's use it in cases where it's
useful.

Author: David Rowley
Discussion: https://postgr.es/m/1986787.1657666922%40sss.pgh.pa.us
This commit is contained in:
David Rowley 2022-07-13 15:03:47 +12:00
parent 50e4c280f0
commit c23e3e6beb
7 changed files with 25 additions and 30 deletions
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8
src/backend/catalog/objectaddress.c
View File

@ -1453,7 +1453,7 @@ get_object_address_relobject(ObjectType objtype, List *object,
errmsg("must specify relation and object name")));
/* Extract relation name and open relation. */
relname = list_truncate(list_copy(object), nnames - 1);
relname = list_copy_head(object, nnames - 1);
relation = table_openrv_extended(makeRangeVarFromNameList(relname),
AccessShareLock,
missing_ok);
@ -1528,7 +1528,7 @@ get_object_address_attribute(ObjectType objtype, List *object,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("column name must be qualified")));
attname = strVal(llast(object));
relname = list_truncate(list_copy(object), list_length(object) - 1);
relname = list_copy_head(object, list_length(object) - 1);
/* XXX no missing_ok support here */
relation = relation_openrv(makeRangeVarFromNameList(relname), lockmode);
reloid = RelationGetRelid(relation);
@ -1581,7 +1581,7 @@ get_object_address_attrdef(ObjectType objtype, List *object,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("column name must be qualified")));
attname = strVal(llast(object));
relname = list_truncate(list_copy(object), list_length(object) - 1);
relname = list_copy_head(object, list_length(object) - 1);
/* XXX no missing_ok support here */
relation = relation_openrv(makeRangeVarFromNameList(relname), lockmode);
reloid = RelationGetRelid(relation);
@ -1715,7 +1715,7 @@ get_object_address_opf_member(ObjectType objtype,
* address. The rest can be used directly by get_object_address_opcf().
*/
membernum = atoi(strVal(llast(linitial(object))));
copy = list_truncate(list_copy(linitial(object)), list_length(linitial(object)) - 1);
copy = list_copy_head(linitial(object), list_length(linitial(object)) - 1);
/* no missing_ok support here */
famaddr = get_object_address_opcf(OBJECT_OPFAMILY, copy, false);

15
src/backend/commands/dropcmds.c
View File

@ -145,8 +145,7 @@ owningrel_does_not_exist_skipping(List *object, const char **msg, char **name)
List *parent_object;
RangeVar *parent_rel;
parent_object = list_truncate(list_copy(object),
list_length(object) - 1);
parent_object = list_copy_head(object, list_length(object) - 1);
if (schema_does_not_exist_skipping(parent_object, msg, name))
return true;
@ -419,8 +418,8 @@ does_not_exist_skipping(ObjectType objtype, Node *object)
{
msg = gettext_noop("trigger \"%s\" for relation \"%s\" does not exist, skipping");
name = strVal(llast(castNode(List, object)));
args = NameListToString(list_truncate(list_copy(castNode(List, object)),
list_length(castNode(List, object)) - 1));
args = NameListToString(list_copy_head(castNode(List, object),
list_length(castNode(List, object)) - 1));
}
break;
case OBJECT_POLICY:
@ -428,8 +427,8 @@ does_not_exist_skipping(ObjectType objtype, Node *object)
{
msg = gettext_noop("policy \"%s\" for relation \"%s\" does not exist, skipping");
name = strVal(llast(castNode(List, object)));
args = NameListToString(list_truncate(list_copy(castNode(List, object)),
list_length(castNode(List, object)) - 1));
args = NameListToString(list_copy_head(castNode(List, object),
list_length(castNode(List, object)) - 1));
}
break;
case OBJECT_EVENT_TRIGGER:
@ -441,8 +440,8 @@ does_not_exist_skipping(ObjectType objtype, Node *object)
{
msg = gettext_noop("rule \"%s\" for relation \"%s\" does not exist, skipping");
name = strVal(llast(castNode(List, object)));
args = NameListToString(list_truncate(list_copy(castNode(List, object)),
list_length(castNode(List, object)) - 1));
args = NameListToString(list_copy_head(castNode(List, object),
list_length(castNode(List, object)) - 1));
}
break;
case OBJECT_FDW:

2
src/backend/commands/sequence.c
View File

@ -1620,7 +1620,7 @@ process_owned_by(Relation seqrel, List *owned_by, bool for_identity)
RangeVar *rel;
/* Separate relname and attr name */
relname = list_truncate(list_copy(owned_by), nnames - 1);
relname = list_copy_head(owned_by, nnames - 1);
attrname = strVal(llast(owned_by));
/* Open and lock rel to ensure it won't go away meanwhile */

9
src/backend/optimizer/path/allpaths.c
View File

@ -2053,9 +2053,8 @@ accumulate_append_subpath(Path *path, List **subpaths, List **special_subpaths)
*subpaths = list_concat(*subpaths,
list_copy_tail(apath->subpaths,
apath->first_partial_path));
new_special_subpaths =
list_truncate(list_copy(apath->subpaths),
apath->first_partial_path);
new_special_subpaths = list_copy_head(apath->subpaths,
apath->first_partial_path);
*special_subpaths = list_concat(*special_subpaths,
new_special_subpaths);
return;
@ -3086,8 +3085,8 @@ get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel,
root->query_pathkeys);
else if (npathkeys > 0)
useful_pathkeys_list = lappend(useful_pathkeys_list,
list_truncate(list_copy(root->query_pathkeys),
npathkeys));
list_copy_head(root->query_pathkeys,
npathkeys));
}
return useful_pathkeys_list;

14
src/backend/optimizer/path/indxpath.c
View File

@ -3026,14 +3026,12 @@ expand_indexqual_rowcompare(PlannerInfo *root,
rc->rctype = (RowCompareType) op_strategy;
rc->opnos = new_ops;
rc->opfamilies = list_truncate(list_copy(clause->opfamilies),
matching_cols);
rc->inputcollids = list_truncate(list_copy(clause->inputcollids),
matching_cols);
rc->largs = list_truncate(copyObject(var_args),
matching_cols);
rc->rargs = list_truncate(copyObject(non_var_args),
matching_cols);
rc->opfamilies = list_copy_head(clause->opfamilies,
matching_cols);
rc->inputcollids = list_copy_head(clause->inputcollids,
matching_cols);
rc->largs = list_copy_head(var_args, matching_cols);
rc->rargs = list_copy_head(non_var_args, matching_cols);
iclause->indexquals = list_make1(make_simple_restrictinfo(root,
(Expr *) rc));
}

2
src/backend/optimizer/path/pathkeys.c
View File

@ -2464,7 +2464,7 @@ truncate_useless_pathkeys(PlannerInfo *root,
else if (nuseful == list_length(pathkeys))
return pathkeys;
else
return list_truncate(list_copy(pathkeys), nuseful);
return list_copy_head(pathkeys, nuseful);
}
/*

5
src/backend/optimizer/plan/createplan.c
View File

@ -1397,8 +1397,7 @@ create_append_plan(PlannerInfo *root, AppendPath *best_path, int flags)
*/
if (tlist_was_changed && (flags & (CP_EXACT_TLIST | CP_SMALL_TLIST)))
{
tlist = list_truncate(list_copy(plan->plan.targetlist),
orig_tlist_length);
tlist = list_copy_head(plan->plan.targetlist, orig_tlist_length);
return inject_projection_plan((Plan *) plan, tlist,
plan->plan.parallel_safe);
}
@ -1557,7 +1556,7 @@ create_merge_append_plan(PlannerInfo *root, MergeAppendPath *best_path,
*/
if (tlist_was_changed && (flags & (CP_EXACT_TLIST | CP_SMALL_TLIST)))
{
tlist = list_truncate(list_copy(plan->targetlist), orig_tlist_length);
tlist = list_copy_head(plan->targetlist, orig_tlist_length);
return inject_projection_plan(plan, tlist, plan->parallel_safe);
}
else