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Allow a partdesc-omitting-partitions to be cached

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Makes partition descriptor acquisition faster during the transient
period in which a partition is in the process of being detached.

This also adds the restriction that only one partition can be in
pending-detach state for a partitioned table.

While at it, return find_inheritance_children() API to what it was
before 71f4c8c6f7, and create a separate
find_inheritance_children_extended() that returns detailed info about
detached partitions.

(This incidentally fixes a bug in 8aba932251 whereby a memory context
holding a transient partdesc is reparented to a NULL PortalContext,
leading to permanent leak of that memory.  The fix is to no longer rely
on reparenting contexts to PortalContext.   Reported by Amit Langote.)

Per gripe from Amit Langote
Discussion: https://postgr.es/m/CA+HiwqFgpP1LxJZOBYGt9rpvTjXXkg5qG2+Xch2Z1Q7KrqZR1A@mail.gmail.com
This commit is contained in:
Alvaro Herrera
2021-04-28 15:44:35 -04:00
parent c93f8f3b8d
commit d6b8d29419
10 changed files with 330 additions and 74 deletions
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52
src/backend/catalog/pg_inherits.c
View File

@@ -52,6 +52,22 @@ typedef struct SeenRelsEntry
* then no locks are acquired, but caller must beware of race conditions
* against possible DROPs of child relations.
*
* Partitions marked as being detached are omitted; see
* find_inheritance_children_extended for details.
*/
List *
find_inheritance_children(Oid parentrelId, LOCKMODE lockmode)
{
return find_inheritance_children_extended(parentrelId, true, lockmode,
NULL, NULL);
}
/*
* find_inheritance_children_extended
*
* As find_inheritance_children, with more options regarding detached
* partitions.
*
* If a partition's pg_inherits row is marked "detach pending",
* *detached_exist (if not null) is set true.
*
@@ -60,11 +76,13 @@ typedef struct SeenRelsEntry
* marked "detach pending" is visible to that snapshot, then that partition is
* omitted from the output list. This makes partitions invisible depending on
* whether the transaction that marked those partitions as detached appears
* committed to the active snapshot.
* committed to the active snapshot. In addition, *detached_xmin (if not null)
* is set to the xmin of the row of the detached partition.
*/
List *
find_inheritance_children(Oid parentrelId, bool omit_detached,
LOCKMODE lockmode, bool *detached_exist)
find_inheritance_children_extended(Oid parentrelId, bool omit_detached,
LOCKMODE lockmode, bool *detached_exist,
TransactionId *detached_xmin)
{
List *list = NIL;
Relation relation;
@@ -132,7 +150,32 @@ find_inheritance_children(Oid parentrelId, bool omit_detached,
snap = GetActiveSnapshot();
if (!XidInMVCCSnapshot(xmin, snap))
{
if (detached_xmin)
{
/*
* Two detached partitions should not occur (see
* checks in MarkInheritDetached), but if they do,
* track the newer of the two. Make sure to warn the
* user, so that they can clean up. Since this is
* just a cross-check against potentially corrupt
* catalogs, we don't make it a full-fledged error
* message.
*/
if (*detached_xmin != InvalidTransactionId)
{
elog(WARNING, "more than one partition pending detach found for table with OID %u",
parentrelId);
if (TransactionIdFollows(xmin, *detached_xmin))
*detached_xmin = xmin;
}
else
*detached_xmin = xmin;
}
/* Don't add the partition to the output list */
continue;
}
}
}
@@ -247,8 +290,7 @@ find_all_inheritors(Oid parentrelId, LOCKMODE lockmode, List **numparents)
ListCell *lc;
/* Get the direct children of this rel */
currentchildren = find_inheritance_children(currentrel, true,
lockmode, NULL);
currentchildren = find_inheritance_children(currentrel, lockmode);
/*
* Add to the queue only those children not already seen. This avoids