/*
* find_all_inheritors -
* Returns a list of relation OIDs including the given rel plus
* all relations that inherit from it, directly or indirectly.
* Optionally, it also returns the number of parents found for
* each such relation within the inheritance tree rooted at the
* given rel.
*
* The specified lock type is acquired on all child relations (but not on the
* given rel; caller should already have locked it). If lockmode is NoLock
* then no locks are acquired, but caller must beware of race conditions
* against possible DROPs of child relations.
*/
List *
find_all_inheritors(Oid parentrelId, LOCKMODE lockmode, List **numparents)
{
List *rels_list,
*rel_numparents;
ListCell *l;
/*
* We build a list starting with the given rel and adding all direct and
* indirect children. We can use a single list as both the record of
* already-found rels and the agenda of rels yet to be scanned for more
* children. This is a bit tricky but works because the foreach() macro
* doesn't fetch the next list element until the bottom of the loop.
*/
rels_list = list_make1_oid(parentrelId);
rel_numparents = list_make1_int(0);
foreach(l, rels_list)
{
Oid currentrel = lfirst_oid(l);
List *currentchildren;
ListCell *lc;
/* Get the direct children of this rel */
currentchildren = find_inheritance_children(currentrel, lockmode);
/*
* Add to the queue only those children not already seen. This avoids
* making duplicate entries in case of multiple inheritance paths from
* the same parent. (It'll also keep us from getting into an infinite
* loop, though theoretically there can't be any cycles in the
* inheritance graph anyway.)
*/
foreach(lc, currentchildren)
{
Oid child_oid = lfirst_oid(lc);
bool found = false;
ListCell *lo;
ListCell *li;
/* if the rel is already there, bump number-of-parents counter */
forboth(lo, rels_list, li, rel_numparents)
{
if (lfirst_oid(lo) == child_oid)
{
lfirst_int(li)++;
found = true;
break;
}
}
/* if it's not there, add it. expect 1 parent, initially. */
if (!found)
{
rels_list = lappend_oid(rels_list, child_oid);
rel_numparents = lappend_int(rel_numparents, 1);
}
}
/*
* find_all_inheritors -
* Returns a list of relation OIDs including the given rel plus
* all relations that inherit from it, directly or indirectly.
* Optionally, it also returns the number of parents found for
* each such relation within the inheritance tree rooted at the
* given rel.
*
* The specified lock type is acquired on all child relations (but not on the
* given rel; caller should already have locked it). If lockmode is NoLock
* then no locks are acquired, but caller must beware of race conditions
* against possible DROPs of child relations.
*/
List *
find_all_inheritors(Oid parentrelId, LOCKMODE lockmode, List **numparents)
{
/* hash table for O(1) rel_oid -> rel_numparents cell lookup */
HTAB *seen_rels;
HASHCTL ctl;
List *rels_list,
*rel_numparents;
ListCell *l;
memset(&ctl, 0, sizeof(ctl));
ctl.keysize = sizeof(Oid);
ctl.entrysize = sizeof(SeenRelsEntry);
ctl.hcxt = CurrentMemoryContext;
seen_rels = hash_create("find_all_inheritors temporary table",
32, /* start small and extend */
&ctl,
HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
/*
* We build a list starting with the given rel and adding all direct and
* indirect children. We can use a single list as both the record of
* already-found rels and the agenda of rels yet to be scanned for more
* children. This is a bit tricky but works because the foreach() macro
* doesn't fetch the next list element until the bottom of the loop.
*/
rels_list = list_make1_oid(parentrelId);
rel_numparents = list_make1_int(0);
foreach(l, rels_list)
{
Oid currentrel = lfirst_oid(l);
List *currentchildren;
ListCell *lc;
/* Get the direct children of this rel */
currentchildren = find_inheritance_children(currentrel, lockmode);
/*
* Add to the queue only those children not already seen. This avoids
* making duplicate entries in case of multiple inheritance paths from
* the same parent. (It'll also keep us from getting into an infinite
* loop, though theoretically there can't be any cycles in the
* inheritance graph anyway.)
*/
foreach(lc, currentchildren)
{
Oid child_oid = lfirst_oid(lc);
bool found;
SeenRelsEntry *hash_entry;
hash_entry = hash_search(seen_rels, &child_oid, HASH_ENTER, &found);
if (found)
{
/* if the rel is already there, bump number-of-parents counter */
lfirst_int(hash_entry->numparents_cell)++;
}
else
{
/* if it's not there, add it. expect 1 parent, initially. */
rels_list = lappend_oid(rels_list, child_oid);
rel_numparents = lappend_int(rel_numparents, 1);
hash_entry->numparents_cell = rel_numparents->tail;
}
}
