/*
* GetCatCacheHashValue
*
* Compute the hash value for a given set of search keys.
*
* The reason for exposing this as part of the API is that the hash value is
* exposed in cache invalidation operations, so there are places outside the
* catcache code that need to be able to compute the hash values.
*/
uint32
GetCatCacheHashValue(CatCache *cache,
Datum v1,
Datum v2,
Datum v3,
Datum v4)
{
ScanKeyData cur_skey[CATCACHE_MAXKEYS];
/*
* one-time startup overhead for each cache
*/
if (cache->cc_tupdesc == NULL)
CatalogCacheInitializeCache(cache);
/*
* initialize the search key information
*/
memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
cur_skey[0].sk_argument = v1;
cur_skey[1].sk_argument = v2;
cur_skey[2].sk_argument = v3;
cur_skey[3].sk_argument = v4;
/*
* calculate the hash value
*/
return CatalogCacheComputeHashValue(cache, cache->cc_nkeys, cur_skey);
}
/*
* CatalogCacheComputeTupleHashValue
*
* Compute the hash value associated with a given tuple to be cached
*/
static uint32
CatalogCacheComputeTupleHashValue(CatCache *cache, HeapTuple tuple)
{
ScanKeyData cur_skey[CATCACHE_MAXKEYS];
bool isNull = false;
/* Copy pre-initialized overhead data for scankey */
memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
/* Now extract key fields from tuple, insert into scankey */
switch (cache->cc_nkeys)
{
case 4:
cur_skey[3].sk_argument =
(cache->cc_key[3] == ObjectIdAttributeNumber)
? ObjectIdGetDatum(HeapTupleGetOid(tuple))
: fastgetattr(tuple,
cache->cc_key[3],
cache->cc_tupdesc,
&isNull);
Assert(!isNull);
/* FALLTHROUGH */
case 3:
cur_skey[2].sk_argument =
(cache->cc_key[2] == ObjectIdAttributeNumber)
? ObjectIdGetDatum(HeapTupleGetOid(tuple))
: fastgetattr(tuple,
cache->cc_key[2],
cache->cc_tupdesc,
&isNull);
Assert(!isNull);
/* FALLTHROUGH */
case 2:
cur_skey[1].sk_argument =
(cache->cc_key[1] == ObjectIdAttributeNumber)
? ObjectIdGetDatum(HeapTupleGetOid(tuple))
: fastgetattr(tuple,
cache->cc_key[1],
cache->cc_tupdesc,
&isNull);
Assert(!isNull);
/* FALLTHROUGH */
case 1:
cur_skey[0].sk_argument =
(cache->cc_key[0] == ObjectIdAttributeNumber)
? ObjectIdGetDatum(HeapTupleGetOid(tuple))
: fastgetattr(tuple,
cache->cc_key[0],
cache->cc_tupdesc,
&isNull);
Assert(!isNull);
break;
default:
elog(FATAL, "wrong number of hash keys: %d", cache->cc_nkeys);
break;
}
return CatalogCacheComputeHashValue(cache, cache->cc_nkeys, cur_skey);
}
/*
* SearchCatCacheList
*
* Generate a list of all tuples matching a partial key (that is,
* a key specifying just the first K of the cache's N key columns).
*
* The caller must not modify the list object or the pointed-to tuples,
* and must call ReleaseCatCacheList() when done with the list.
*/
CatCList *
SearchCatCacheList(CatCache *cache,
int nkeys,
Datum v1,
Datum v2,
Datum v3,
Datum v4)
{
ScanKeyData cur_skey[CATCACHE_MAXKEYS];
uint32 lHashValue;
Dlelem *elt;
CatCList *cl;
CatCTup *ct;
List *volatile ctlist;
ListCell *ctlist_item;
int nmembers;
bool ordered;
HeapTuple ntp;
MemoryContext oldcxt;
int i;
/*
* one-time startup overhead for each cache
*/
if (cache->cc_tupdesc == NULL)
CatalogCacheInitializeCache(cache);
Assert(nkeys > 0 && nkeys < cache->cc_nkeys);
#ifdef CATCACHE_STATS
cache->cc_lsearches++;
#endif
/*
* initialize the search key information
*/
memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
cur_skey[0].sk_argument = v1;
cur_skey[1].sk_argument = v2;
cur_skey[2].sk_argument = v3;
cur_skey[3].sk_argument = v4;
/*
* compute a hash value of the given keys for faster search. We don't
* presently divide the CatCList items into buckets, but this still lets
* us skip non-matching items quickly most of the time.
*/
lHashValue = CatalogCacheComputeHashValue(cache, nkeys, cur_skey);
/*
* scan the items until we find a match or exhaust our list
*/
for (elt = DLGetHead(&cache->cc_lists);
elt;
elt = DLGetSucc(elt))
{
bool res;
cl = (CatCList *) DLE_VAL(elt);
if (cl->dead)
continue; /* ignore dead entries */
if (cl->hash_value != lHashValue)
continue; /* quickly skip entry if wrong hash val */
/*
* see if the cached list matches our key.
*/
if (cl->nkeys != nkeys)
continue;
HeapKeyTest(&cl->tuple,
cache->cc_tupdesc,
nkeys,
cur_skey,
res);
if (!res)
continue;
/*
* We found a matching list. Move the list to the front of the
* cache's list-of-lists, to speed subsequent searches. (We do not
* move the members to the fronts of their hashbucket lists, however,
* since there's no point in that unless they are searched for
* individually.)
*/
DLMoveToFront(&cl->cache_elem);
/* Bump the list's refcount and return it */
ResourceOwnerEnlargeCatCacheListRefs(CurrentResourceOwner);
cl->refcount++;
ResourceOwnerRememberCatCacheListRef(CurrentResourceOwner, cl);
CACHE2_elog(DEBUG2, "SearchCatCacheList(%s): found list",
cache->cc_relname);
#ifdef CATCACHE_STATS
cache->cc_lhits++;
#endif
return cl;
}
/*
* List was not found in cache, so we have to build it by reading the
* relation. For each matching tuple found in the relation, use an
* existing cache entry if possible, else build a new one.
*
* We have to bump the member refcounts temporarily to ensure they won't
* get dropped from the cache while loading other members. We use a PG_TRY
* block to ensure we can undo those refcounts if we get an error before
* we finish constructing the CatCList.
*/
ResourceOwnerEnlargeCatCacheListRefs(CurrentResourceOwner);
ctlist = NIL;
PG_TRY();
{
Relation relation;
SysScanDesc scandesc;
relation = heap_open(cache->cc_reloid, AccessShareLock);
scandesc = systable_beginscan(relation,
cache->cc_indexoid,
IndexScanOK(cache, cur_skey),
SnapshotNow,
nkeys,
cur_skey);
/* The list will be ordered iff we are doing an index scan */
ordered = (scandesc->irel != NULL);
while (HeapTupleIsValid(ntp = systable_getnext(scandesc)))
{
uint32 hashValue;
Index hashIndex;
/*
* See if there's an entry for this tuple already.
*/
ct = NULL;
hashValue = CatalogCacheComputeTupleHashValue(cache, ntp);
hashIndex = HASH_INDEX(hashValue, cache->cc_nbuckets);
for (elt = DLGetHead(&cache->cc_bucket[hashIndex]);
elt;
elt = DLGetSucc(elt))
{
ct = (CatCTup *) DLE_VAL(elt);
if (ct->dead || ct->negative)
continue; /* ignore dead and negative entries */
if (ct->hash_value != hashValue)
continue; /* quickly skip entry if wrong hash val */
if (!ItemPointerEquals(&(ct->tuple.t_self), &(ntp->t_self)))
continue; /* not same tuple */
/*
* Found a match, but can't use it if it belongs to another
* list already
*/
if (ct->c_list)
continue;
break; /* A-OK */
}
if (elt == NULL)
{
/* We didn't find a usable entry, so make a new one */
ct = CatalogCacheCreateEntry(cache, ntp,
hashValue, hashIndex,
false);
}
/* Careful here: add entry to ctlist, then bump its refcount */
/* This way leaves state correct if lappend runs out of memory */
ctlist = lappend(ctlist, ct);
ct->refcount++;
}
systable_endscan(scandesc);
heap_close(relation, AccessShareLock);
/*
* Now we can build the CatCList entry. First we need a dummy tuple
* containing the key values...
*/
ntp = build_dummy_tuple(cache, nkeys, cur_skey);
oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
nmembers = list_length(ctlist);
cl = (CatCList *)
palloc(sizeof(CatCList) + nmembers * sizeof(CatCTup *));
heap_copytuple_with_tuple(ntp, &cl->tuple);
MemoryContextSwitchTo(oldcxt);
heap_freetuple(ntp);
/*
* We are now past the last thing that could trigger an elog before we
* have finished building the CatCList and remembering it in the
* resource owner. So it's OK to fall out of the PG_TRY, and indeed
* we'd better do so before we start marking the members as belonging
* to the list.
*/
}
PG_CATCH();
{
foreach(ctlist_item, ctlist)
{
ct = (CatCTup *) lfirst(ctlist_item);
Assert(ct->c_list == NULL);
Assert(ct->refcount > 0);
ct->refcount--;
if (
#ifndef CATCACHE_FORCE_RELEASE
ct->dead &&
#endif
ct->refcount == 0 &&
(ct->c_list == NULL || ct->c_list->refcount == 0))
CatCacheRemoveCTup(cache, ct);
}
PG_RE_THROW();
}
/*
* SearchCatCache
*
* This call searches a system cache for a tuple, opening the relation
* if necessary (on the first access to a particular cache).
*
* The result is NULL if not found, or a pointer to a HeapTuple in
* the cache. The caller must not modify the tuple, and must call
* ReleaseCatCache() when done with it.
*
* The search key values should be expressed as Datums of the key columns'
* datatype(s). (Pass zeroes for any unused parameters.) As a special
* exception, the passed-in key for a NAME column can be just a C string;
* the caller need not go to the trouble of converting it to a fully
* null-padded NAME.
*/
HeapTuple
SearchCatCache(CatCache *cache,
Datum v1,
Datum v2,
Datum v3,
Datum v4)
{
ScanKeyData cur_skey[CATCACHE_MAXKEYS];
uint32 hashValue;
Index hashIndex;
Dlelem *elt;
CatCTup *ct;
Relation relation;
SysScanDesc scandesc;
HeapTuple ntp;
/*
* one-time startup overhead for each cache
*/
if (cache->cc_tupdesc == NULL)
CatalogCacheInitializeCache(cache);
#ifdef CATCACHE_STATS
cache->cc_searches++;
#endif
/*
* initialize the search key information
*/
memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
cur_skey[0].sk_argument = v1;
cur_skey[1].sk_argument = v2;
cur_skey[2].sk_argument = v3;
cur_skey[3].sk_argument = v4;
/*
* find the hash bucket in which to look for the tuple
*/
hashValue = CatalogCacheComputeHashValue(cache, cache->cc_nkeys, cur_skey);
hashIndex = HASH_INDEX(hashValue, cache->cc_nbuckets);
/*
* scan the hash bucket until we find a match or exhaust our tuples
*/
for (elt = DLGetHead(&cache->cc_bucket[hashIndex]);
elt;
elt = DLGetSucc(elt))
{
bool res;
ct = (CatCTup *) DLE_VAL(elt);
if (ct->dead)
continue; /* ignore dead entries */
if (ct->hash_value != hashValue)
continue; /* quickly skip entry if wrong hash val */
/*
* see if the cached tuple matches our key.
*/
HeapKeyTest(&ct->tuple,
cache->cc_tupdesc,
cache->cc_nkeys,
cur_skey,
res);
if (!res)
continue;
/*
* We found a match in the cache. Move it to the front of the list
* for its hashbucket, in order to speed subsequent searches. (The
* most frequently accessed elements in any hashbucket will tend to be
* near the front of the hashbucket's list.)
*/
DLMoveToFront(&ct->cache_elem);
/*
* If it's a positive entry, bump its refcount and return it. If it's
* negative, we can report failure to the caller.
*/
if (!ct->negative)
{
ResourceOwnerEnlargeCatCacheRefs(CurrentResourceOwner);
ct->refcount++;
ResourceOwnerRememberCatCacheRef(CurrentResourceOwner, &ct->tuple);
CACHE3_elog(DEBUG2, "SearchCatCache(%s): found in bucket %d",
cache->cc_relname, hashIndex);
#ifdef CATCACHE_STATS
cache->cc_hits++;
#endif
return &ct->tuple;
}
else
{
CACHE3_elog(DEBUG2, "SearchCatCache(%s): found neg entry in bucket %d",
cache->cc_relname, hashIndex);
#ifdef CATCACHE_STATS
cache->cc_neg_hits++;
#endif
return NULL;
}
}
/*
* Tuple was not found in cache, so we have to try to retrieve it directly
* from the relation. If found, we will add it to the cache; if not
* found, we will add a negative cache entry instead.
*
* NOTE: it is possible for recursive cache lookups to occur while reading
* the relation --- for example, due to shared-cache-inval messages being
* processed during heap_open(). This is OK. It's even possible for one
* of those lookups to find and enter the very same tuple we are trying to
* fetch here. If that happens, we will enter a second copy of the tuple
* into the cache. The first copy will never be referenced again, and
* will eventually age out of the cache, so there's no functional problem.
* This case is rare enough that it's not worth expending extra cycles to
* detect.
*/
relation = heap_open(cache->cc_reloid, AccessShareLock);
scandesc = systable_beginscan(relation,
cache->cc_indexoid,
IndexScanOK(cache, cur_skey),
SnapshotNow,
cache->cc_nkeys,
cur_skey);
ct = NULL;
while (HeapTupleIsValid(ntp = systable_getnext(scandesc)))
{
ct = CatalogCacheCreateEntry(cache, ntp,
hashValue, hashIndex,
false);
/* immediately set the refcount to 1 */
ResourceOwnerEnlargeCatCacheRefs(CurrentResourceOwner);
ct->refcount++;
ResourceOwnerRememberCatCacheRef(CurrentResourceOwner, &ct->tuple);
break; /* assume only one match */
}
systable_endscan(scandesc);
heap_close(relation, AccessShareLock);
/*
* If tuple was not found, we need to build a negative cache entry
* containing a fake tuple. The fake tuple has the correct key columns,
* but nulls everywhere else.
*
* In bootstrap mode, we don't build negative entries, because the cache
* invalidation mechanism isn't alive and can't clear them if the tuple
* gets created later. (Bootstrap doesn't do UPDATEs, so it doesn't need
* cache inval for that.)
*/
if (ct == NULL)
{
if (IsBootstrapProcessingMode())
return NULL;
ntp = build_dummy_tuple(cache, cache->cc_nkeys, cur_skey);
ct = CatalogCacheCreateEntry(cache, ntp,
hashValue, hashIndex,
true);
heap_freetuple(ntp);
CACHE4_elog(DEBUG2, "SearchCatCache(%s): Contains %d/%d tuples",
cache->cc_relname, cache->cc_ntup, CacheHdr->ch_ntup);
CACHE3_elog(DEBUG2, "SearchCatCache(%s): put neg entry in bucket %d",
cache->cc_relname, hashIndex);
/*
* We are not returning the negative entry to the caller, so leave its
* refcount zero.
*/
return NULL;
}
CACHE4_elog(DEBUG2, "SearchCatCache(%s): Contains %d/%d tuples",
cache->cc_relname, cache->cc_ntup, CacheHdr->ch_ntup);
CACHE3_elog(DEBUG2, "SearchCatCache(%s): put in bucket %d",
cache->cc_relname, hashIndex);
#ifdef CATCACHE_STATS
cache->cc_newloads++;
#endif
return &ct->tuple;
}
/*
* SearchCatCacheList
*
* Generate a list of all tuples matching a partial key (that is,
* a key specifying just the first K of the cache's N key columns).
*
* The caller must not modify the list object or the pointed-to tuples,
* and must call ReleaseCatCacheList() when done with the list.
*/
CatCList *
SearchCatCacheList(CatCache *cache,
int nkeys,
Datum v1,
Datum v2,
Datum v3,
Datum v4)
{
ScanKeyData cur_skey[4];
uint32 lHashValue;
Dlelem *elt;
CatCList *cl;
CatCTup *ct;
List *ctlist;
int nmembers;
Relation relation;
SysScanDesc scandesc;
bool ordered;
HeapTuple ntp;
MemoryContext oldcxt;
int i;
/*
* one-time startup overhead for each cache
*/
if (cache->cc_tupdesc == NULL)
CatalogCacheInitializeCache(cache);
Assert(nkeys > 0 && nkeys < cache->cc_nkeys);
#ifdef CATCACHE_STATS
cache->cc_lsearches++;
#endif
/*
* initialize the search key information
*/
memcpy(cur_skey, cache->cc_skey, sizeof(cur_skey));
cur_skey[0].sk_argument = v1;
cur_skey[1].sk_argument = v2;
cur_skey[2].sk_argument = v3;
cur_skey[3].sk_argument = v4;
/*
* compute a hash value of the given keys for faster search. We don't
* presently divide the CatCList items into buckets, but this still
* lets us skip non-matching items quickly most of the time.
*/
lHashValue = CatalogCacheComputeHashValue(cache, nkeys, cur_skey);
/*
* scan the items until we find a match or exhaust our list
*/
for (elt = DLGetHead(&cache->cc_lists);
elt;
elt = DLGetSucc(elt))
{
bool res;
cl = (CatCList *) DLE_VAL(elt);
if (cl->dead)
continue; /* ignore dead entries */
if (cl->hash_value != lHashValue)
continue; /* quickly skip entry if wrong hash val */
/*
* see if the cached list matches our key.
*/
if (cl->nkeys != nkeys)
continue;
HeapKeyTest(&cl->tuple,
cache->cc_tupdesc,
nkeys,
cur_skey,
res);
if (!res)
continue;
/*
* we found a matching list: move each of its members to the front
* of the global LRU list. Also move the list itself to the front
* of the cache's list-of-lists, to speed subsequent searches. (We
* do not move the members to the fronts of their hashbucket
* lists, however, since there's no point in that unless they are
* searched for individually.) Also bump the members' refcounts.
*/
for (i = 0; i < cl->n_members; i++)
{
cl->members[i]->refcount++;
DLMoveToFront(&cl->members[i]->lrulist_elem);
}
DLMoveToFront(&cl->cache_elem);
/* Bump the list's refcount and return it */
cl->refcount++;
CACHE2_elog(DEBUG2, "SearchCatCacheList(%s): found list",
cache->cc_relname);
#ifdef CATCACHE_STATS
cache->cc_lhits++;
#endif
return cl;
}
/*
* List was not found in cache, so we have to build it by reading the
* relation. For each matching tuple found in the relation, use an
* existing cache entry if possible, else build a new one.
*/
relation = heap_open(cache->cc_reloid, AccessShareLock);
scandesc = systable_beginscan(relation,
cache->cc_indname,
true,
SnapshotNow,
nkeys,
cur_skey);
/* The list will be ordered iff we are doing an index scan */
ordered = (scandesc->irel != NULL);
ctlist = NIL;
nmembers = 0;
while (HeapTupleIsValid(ntp = systable_getnext(scandesc)))
{
uint32 hashValue;
Index hashIndex;
/*
* See if there's an entry for this tuple already.
*/
ct = NULL;
hashValue = CatalogCacheComputeTupleHashValue(cache, ntp);
hashIndex = HASH_INDEX(hashValue, cache->cc_nbuckets);
for (elt = DLGetHead(&cache->cc_bucket[hashIndex]);
elt;
elt = DLGetSucc(elt))
{
ct = (CatCTup *) DLE_VAL(elt);
if (ct->dead || ct->negative)
continue; /* ignore dead and negative entries */
if (ct->hash_value != hashValue)
continue; /* quickly skip entry if wrong hash val */
if (!ItemPointerEquals(&(ct->tuple.t_self), &(ntp->t_self)))
continue; /* not same tuple */
/*
* Found a match, but can't use it if it belongs to another
* list already
*/
if (ct->c_list)
continue;
/* Found a match, so bump its refcount and move to front */
ct->refcount++;
DLMoveToFront(&ct->lrulist_elem);
break;
}
if (elt == NULL)
{
/* We didn't find a usable entry, so make a new one */
ct = CatalogCacheCreateEntry(cache, ntp,
hashValue, hashIndex,
false);
}
ctlist = lcons(ct, ctlist);
nmembers++;
}
systable_endscan(scandesc);
heap_close(relation, AccessShareLock);
/*
* Now we can build the CatCList entry. First we need a dummy tuple
* containing the key values...
*/
ntp = build_dummy_tuple(cache, nkeys, cur_skey);
oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
cl = (CatCList *) palloc(sizeof(CatCList) + nmembers * sizeof(CatCTup *));
heap_copytuple_with_tuple(ntp, &cl->tuple);
MemoryContextSwitchTo(oldcxt);
heap_freetuple(ntp);
cl->cl_magic = CL_MAGIC;
cl->my_cache = cache;
DLInitElem(&cl->cache_elem, (void *) cl);
cl->refcount = 1; /* count this first reference */
cl->dead = false;
cl->ordered = ordered;
cl->nkeys = nkeys;
cl->hash_value = lHashValue;
cl->n_members = nmembers;
/* The list is backwards because we built it with lcons */
for (i = nmembers; --i >= 0;)
{
cl->members[i] = ct = (CatCTup *) lfirst(ctlist);
Assert(ct->c_list == NULL);
ct->c_list = cl;
/* mark list dead if any members already dead */
if (ct->dead)
cl->dead = true;
ctlist = lnext(ctlist);
}
DLAddHead(&cache->cc_lists, &cl->cache_elem);
CACHE3_elog(DEBUG2, "SearchCatCacheList(%s): made list of %d members",
cache->cc_relname, nmembers);
return cl;
}
