Avoid searching for the target catcache in CatalogCacheIdInvalidate.

A test case provided by Mathieu Fenniak shows that the initial search for
the target catcache in CatalogCacheIdInvalidate consumes a very significant
amount of overhead in cases where cache invalidation is triggered but has
little useful work to do.  There is no good reason for that search to exist
at all, as the index array maintained by syscache.c allows direct lookup of
the catcache from its ID.  We just need a frontend function in syscache.c,
matching the division of labor for most other cache-accessing operations.

While there's more that can be done in this area, this patch alone reduces
the runtime of Mathieu's example by 2X.  We can hope that it offers some
useful benefit in other cases too, although usually cache invalidation
overhead is not such a striking fraction of the total runtime.

Back-patch to 9.4 where logical decoding was introduced.  It might be
worth going further back, but presently the only case we know of where
cache invalidation is really a significant burden is in logical decoding.
Also, older branches have fewer catcaches, reducing the possible benefit.

(Note: although this nominally changes catcache's API, we have always
documented CatalogCacheIdInvalidate as a private function, so I would
have little sympathy for an external module calling it directly.  So
backpatching should be fine.)

Discussion: https://postgr.es/m/CAHoiPjzea6N0zuCi=+f9v_j94nfsy6y8SU7-=bp4=7qw6_i=Rg@mail.gmail.com

diff --git a/src/backend/utils/cache/catcache.c b/src/backend/utils/cache/catcache.c
index 954b435bffa7fa6d0bbfe13b076f1319c71444b1..db4599ec4a38acb9602459e90a026e66eaae87b8 100644 (file)
--- a/src/backend/utils/cache/catcache.c
+++ b/src/backend/utils/cache/catcache.c
@@ -425,7 +425,7 @@ CatCacheRemoveCList(CatCache *cache, CatCList *cl)
 
 
 /*
- * CatalogCacheIdInvalidate
+ * CatCacheInvalidate
  *
  * Invalidate entries in the specified cache, given a hash value.
  *
@@ -443,71 +443,57 @@ CatCacheRemoveCList(CatCache *cache, CatCList *cl)
  * This routine is only quasi-public: it should only be used by inval.c.
  */
 void
-CatalogCacheIdInvalidate(int cacheId, uint32 hashValue)
+CatCacheInvalidate(CatCache *cache, uint32 hashValue)
 {
-   slist_iter  cache_iter;
+   Index       hashIndex;
+   dlist_mutable_iter iter;
 
-   CACHE1_elog(DEBUG2, "CatalogCacheIdInvalidate: called");
+   CACHE1_elog(DEBUG2, "CatCacheInvalidate: called");
 
    /*
-    * inspect caches to find the proper cache
+    * We don't bother to check whether the cache has finished initialization
+    * yet; if not, there will be no entries in it so no problem.
     */
-   slist_foreach(cache_iter, &CacheHdr->ch_caches)
-   {
-       CatCache   *ccp = slist_container(CatCache, cc_next, cache_iter.cur);
-       Index       hashIndex;
-       dlist_mutable_iter iter;
-
-       if (cacheId != ccp->id)
-           continue;
 
-       /*
-        * We don't bother to check whether the cache has finished
-        * initialization yet; if not, there will be no entries in it so no
-        * problem.
-        */
+   /*
+    * Invalidate *all* CatCLists in this cache; it's too hard to tell which
+    * searches might still be correct, so just zap 'em all.
+    */
+   dlist_foreach_modify(iter, &cache->cc_lists)
+   {
+       CatCList   *cl = dlist_container(CatCList, cache_elem, iter.cur);
 
-       /*
-        * Invalidate *all* CatCLists in this cache; it's too hard to tell
-        * which searches might still be correct, so just zap 'em all.
-        */
-       dlist_foreach_modify(iter, &ccp->cc_lists)
-       {
-           CatCList   *cl = dlist_container(CatCList, cache_elem, iter.cur);
+       if (cl->refcount > 0)
+           cl->dead = true;
+       else
+           CatCacheRemoveCList(cache, cl);
+   }
 
-           if (cl->refcount > 0)
-               cl->dead = true;
-           else
-               CatCacheRemoveCList(ccp, cl);
-       }
+   /*
+    * inspect the proper hash bucket for tuple matches
+    */
+   hashIndex = HASH_INDEX(hashValue, cache->cc_nbuckets);
+   dlist_foreach_modify(iter, &cache->cc_bucket[hashIndex])
+   {
+       CatCTup    *ct = dlist_container(CatCTup, cache_elem, iter.cur);
 
-       /*
-        * inspect the proper hash bucket for tuple matches
-        */
-       hashIndex = HASH_INDEX(hashValue, ccp->cc_nbuckets);
-       dlist_foreach_modify(iter, &ccp->cc_bucket[hashIndex])
+       if (hashValue == ct->hash_value)
        {
-           CatCTup    *ct = dlist_container(CatCTup, cache_elem, iter.cur);
-
-           if (hashValue == ct->hash_value)
+           if (ct->refcount > 0 ||
+               (ct->c_list && ct->c_list->refcount > 0))
            {
-               if (ct->refcount > 0 ||
-                   (ct->c_list && ct->c_list->refcount > 0))
-               {
-                   ct->dead = true;
-                   /* list, if any, was marked dead above */
-                   Assert(ct->c_list == NULL || ct->c_list->dead);
-               }
-               else
-                   CatCacheRemoveCTup(ccp, ct);
-               CACHE1_elog(DEBUG2, "CatalogCacheIdInvalidate: invalidated");
+               ct->dead = true;
+               /* list, if any, was marked dead above */
+               Assert(ct->c_list == NULL || ct->c_list->dead);
+           }
+           else
+               CatCacheRemoveCTup(cache, ct);
+           CACHE1_elog(DEBUG2, "CatCacheInvalidate: invalidated");
 #ifdef CATCACHE_STATS
-               ccp->cc_invals++;
+           cache->cc_invals++;
 #endif
-               /* could be multiple matches, so keep looking! */
-           }
+           /* could be multiple matches, so keep looking! */
        }
-       break;                  /* need only search this one cache */
    }
 }
 
@@ -1815,7 +1801,7 @@ build_dummy_tuple(CatCache *cache, int nkeys, ScanKey skeys)
  * the specified relation, find all catcaches it could be in, compute the
  * correct hash value for each such catcache, and call the specified
  * function to record the cache id and hash value in inval.c's lists.
- * CatalogCacheIdInvalidate will be called later, if appropriate,
+ * SysCacheInvalidate will be called later, if appropriate,
  * using the recorded information.
  *
  * For an insert or delete, tuple is the target tuple and newtuple is NULL.

diff --git a/src/backend/utils/cache/inval.c b/src/backend/utils/cache/inval.c
index c75c2d4609dc7d81a337151fb71a9b85c03fcc7a..47948e4bb7ef147a3596bd8a311b96d4ddfe22ed 100644 (file)
--- a/src/backend/utils/cache/inval.c
+++ b/src/backend/utils/cache/inval.c
@@ -542,7 +542,7 @@ LocalExecuteInvalidationMessage(SharedInvalidationMessage *msg)
        {
            InvalidateCatalogSnapshot();
 
-           CatalogCacheIdInvalidate(msg->cc.id, msg->cc.hashValue);
+           SysCacheInvalidate(msg->cc.id, msg->cc.hashValue);
 
            CallSyscacheCallbacks(msg->cc.id, msg->cc.hashValue);
        }

diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index 81cde1295f332246972e3e45a057f8e930e1583c..8011924fa3ecd06ce913c1891fd37abbd054c82b 100644 (file)
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -1165,6 +1165,27 @@ SearchSysCacheList(int cacheId, int nkeys,
                              key1, key2, key3, key4);
 }
 
+/*
+ * SysCacheInvalidate
+ *
+ * Invalidate entries in the specified cache, given a hash value.
+ * See CatCacheInvalidate() for more info.
+ *
+ * This routine is only quasi-public: it should only be used by inval.c.
+ */
+void
+SysCacheInvalidate(int cacheId, uint32 hashValue)
+{
+   if (cacheId < 0 || cacheId >= SysCacheSize)
+       elog(ERROR, "invalid cache ID: %d", cacheId);
+
+   /* if this cache isn't initialized yet, no need to do anything */
+   if (!PointerIsValid(SysCache[cacheId]))
+       return;
+
+   CatCacheInvalidate(SysCache[cacheId], hashValue);
+}
+
 /*
  * Certain relations that do not have system caches send snapshot invalidation
  * messages in lieu of catcache messages.  This is for the benefit of

diff --git a/src/include/utils/catcache.h b/src/include/utils/catcache.h
index 697516b81ba8fbccadee760dcae149c075313a77..4b3344d24777838a2b514fce869bee058288a9a5 100644 (file)
--- a/src/include/utils/catcache.h
+++ b/src/include/utils/catcache.h
@@ -185,7 +185,7 @@ extern void ReleaseCatCacheList(CatCList *list);
 
 extern void ResetCatalogCaches(void);
 extern void CatalogCacheFlushCatalog(Oid catId);
-extern void CatalogCacheIdInvalidate(int cacheId, uint32 hashValue);
+extern void CatCacheInvalidate(CatCache *cache, uint32 hashValue);
 extern void PrepareToInvalidateCacheTuple(Relation relation,
                              HeapTuple tuple,
                              HeapTuple newtuple,

diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index f41a9968fdc3de34cc1ca5b1346cd6a3536626c7..18e874243445c15a11b1770c2ef3c3ce094f37f5 100644 (file)
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -125,6 +125,8 @@ struct catclist;
 extern struct catclist *SearchSysCacheList(int cacheId, int nkeys,
                   Datum key1, Datum key2, Datum key3, Datum key4);
 
+extern void SysCacheInvalidate(int cacheId, uint32 hashValue);
+
 extern bool RelationInvalidatesSnapshotsOnly(Oid relid);
 extern bool RelationHasSysCache(Oid relid);
 extern bool RelationSupportsSysCache(Oid relid);