heap.c and relcache.c contained nearly identical copies of logic
to insert OIDs into an OID list while preserving the list's OID
ordering (and rejecting duplicates, in one case but not the other).
The comments argue that this is faster than qsort for small numbers
of OIDs, which is at best unproven, and seems even less likely to be
true now that lappend_cell_oid has to move data around. In any case
it's ugly and hard-to-follow code, and if we do have a lot of OIDs
to consider, it's O(N^2).
Hence, replace with simply lappend'ing OIDs to a List, then list_sort
the completed List, then remove adjacent duplicates if necessary.
This is demonstrably O(N log N) and it's much simpler for the
callers. It's possible that this would be somewhat inefficient
if there were a very large number of duplicates, but that seems
unlikely in the existing usage.
This adds list_deduplicate_oid and list_oid_cmp infrastructure
to list.c. I didn't bother with equivalent functionality for
integer or pointer Lists, but such could always be added later
if we find a use for it.
Discussion: https://postgr.es/m/26193.
1563228600@sss.pgh.pa.us
static Node *cookConstraint(ParseState *pstate,
Node *raw_constraint,
char *relname);
-static List *insert_ordered_unique_oid(List *list, Oid datum);
/* ----------------------------------------------------------------
if (!list_member_oid(relationIds, con->confrelid))
continue;
- /* Add referencer unless already in input or result list */
+ /* Add referencer to result, unless present in input list */
if (!list_member_oid(relationIds, con->conrelid))
- result = insert_ordered_unique_oid(result, con->conrelid);
+ result = lappend_oid(result, con->conrelid);
}
systable_endscan(fkeyScan);
table_close(fkeyRel, AccessShareLock);
- return result;
-}
+ /* Now sort and de-duplicate the result list */
+ list_sort(result, list_oid_cmp);
+ list_deduplicate_oid(result);
-/*
- * insert_ordered_unique_oid
- * Insert a new Oid into a sorted list of Oids, preserving ordering,
- * and eliminating duplicates
- *
- * Building the ordered list this way is O(N^2), but with a pretty small
- * constant, so for the number of entries we expect it will probably be
- * faster than trying to apply qsort(). It seems unlikely someone would be
- * trying to truncate a table with thousands of dependent tables ...
- */
-static List *
-insert_ordered_unique_oid(List *list, Oid datum)
-{
- ListCell *prev;
-
- /* Does the datum belong at the front? */
- if (list == NIL || datum < linitial_oid(list))
- return lcons_oid(datum, list);
- /* Does it match the first entry? */
- if (datum == linitial_oid(list))
- return list; /* duplicate, so don't insert */
- /* No, so find the entry it belongs after */
- prev = list_head(list);
- for (;;)
- {
- ListCell *curr = lnext(list, prev);
-
- if (curr == NULL || datum < lfirst_oid(curr))
- break; /* it belongs after 'prev', before 'curr' */
-
- if (datum == lfirst_oid(curr))
- return list; /* duplicate, so don't insert */
-
- prev = curr;
- }
- /* Insert datum into list after 'prev' */
- lappend_cell_oid(list, prev, datum);
- return list;
+ return result;
}
/*
return list1;
}
+/*
+ * Remove adjacent duplicates in a list of OIDs.
+ *
+ * It is caller's responsibility to have sorted the list to bring duplicates
+ * together, perhaps via list_sort(list, list_oid_cmp).
+ */
+void
+list_deduplicate_oid(List *list)
+{
+ int len;
+
+ Assert(IsOidList(list));
+ len = list_length(list);
+ if (len > 1)
+ {
+ ListCell *elements = list->elements;
+ int i = 0;
+
+ for (int j = 1; j < len; j++)
+ {
+ if (elements[i].oid_value != elements[j].oid_value)
+ elements[++i].oid_value = elements[j].oid_value;
+ }
+ list->length = i + 1;
+ }
+ check_list_invariants(list);
+}
+
/*
* Free all storage in a list, and optionally the pointed-to elements
*/
if (len > 1)
qsort(list->elements, len, sizeof(ListCell), (qsort_comparator) cmp);
}
+
+/*
+ * list_sort comparator for sorting a list into ascending OID order.
+ */
+int
+list_oid_cmp(const ListCell *p1, const ListCell *p2)
+{
+ Oid v1 = lfirst_oid(p1);
+ Oid v2 = lfirst_oid(p2);
+
+ if (v1 < v2)
+ return -1;
+ if (v1 > v2)
+ return 1;
+ return 0;
+}
static void AttrDefaultFetch(Relation relation);
static void CheckConstraintFetch(Relation relation);
static int CheckConstraintCmp(const void *a, const void *b);
-static List *insert_ordered_oid(List *list, Oid datum);
static void InitIndexAmRoutine(Relation relation);
static void IndexSupportInitialize(oidvector *indclass,
RegProcedure *indexSupport,
if (!index->indislive)
continue;
- /* Add index's OID to result list in the proper order */
- result = insert_ordered_oid(result, index->indexrelid);
+ /* add index's OID to result list */
+ result = lappend_oid(result, index->indexrelid);
/*
* Invalid, non-unique, non-immediate or predicate indexes aren't
table_close(indrel, AccessShareLock);
+ /* Sort the result list into OID order, per API spec. */
+ list_sort(result, list_oid_cmp);
+
/* Now save a copy of the completed list in the relcache entry. */
oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
oldlist = relation->rd_indexlist;
{
Oid oid = ((Form_pg_statistic_ext) GETSTRUCT(htup))->oid;
- result = insert_ordered_oid(result, oid);
+ result = lappend_oid(result, oid);
}
systable_endscan(indscan);
table_close(indrel, AccessShareLock);
+ /* Sort the result list into OID order, per API spec. */
+ list_sort(result, list_oid_cmp);
+
/* Now save a copy of the completed list in the relcache entry. */
oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
oldlist = relation->rd_statlist;
return result;
}
-/*
- * insert_ordered_oid
- * Insert a new Oid into a sorted list of Oids, preserving ordering
- *
- * Building the ordered list this way is O(N^2), but with a pretty small
- * constant, so for the number of entries we expect it will probably be
- * faster than trying to apply qsort(). Most tables don't have very many
- * indexes...
- */
-static List *
-insert_ordered_oid(List *list, Oid datum)
-{
- ListCell *prev;
-
- /* Does the datum belong at the front? */
- if (list == NIL || datum < linitial_oid(list))
- return lcons_oid(datum, list);
- /* No, so find the entry it belongs after */
- prev = list_head(list);
- for (;;)
- {
- ListCell *curr = lnext(list, prev);
-
- if (curr == NULL || datum < lfirst_oid(curr))
- break; /* it belongs after 'prev', before 'curr' */
-
- prev = curr;
- }
- /* Insert datum into list after 'prev' */
- lappend_cell_oid(list, prev, datum);
- return list;
-}
-
/*
* RelationGetPrimaryKeyIndex -- get OID of the relation's primary key index
*
extern List *list_concat_unique_int(List *list1, const List *list2);
extern List *list_concat_unique_oid(List *list1, const List *list2);
+extern void list_deduplicate_oid(List *list);
+
extern void list_free(List *list);
extern void list_free_deep(List *list);
typedef int (*list_sort_comparator) (const ListCell *a, const ListCell *b);
extern void list_sort(List *list, list_sort_comparator cmp);
+extern int list_oid_cmp(const ListCell *p1, const ListCell *p2);
+
#endif /* PG_LIST_H */
projects / postgresql / commitdiff