/*------------------------------------------------------------------------- * * inval.c * POSTGRES cache invalidation dispatcher code. * * This is subtle stuff, so pay attention: * * When a tuple is updated or deleted, our standard time qualification rules * consider that it is *still valid* so long as we are in the same command, * ie, until the next CommandCounterIncrement() or transaction commit. * (See utils/time/tqual.c, and note that system catalogs are generally * scanned under SnapshotNow rules by the system, or plain user snapshots * for user queries.) At the command boundary, the old tuple stops * being valid and the new version, if any, becomes valid. Therefore, * we cannot simply flush a tuple from the system caches during heap_update() * or heap_delete(). The tuple is still good at that point; what's more, * even if we did flush it, it might be reloaded into the caches by a later * request in the same command. So the correct behavior is to keep a list * of outdated (updated/deleted) tuples and then do the required cache * flushes at the next command boundary. We must also keep track of * inserted tuples so that we can flush "negative" cache entries that match * the new tuples; again, that mustn't happen until end of command. * * Once we have finished the command, we still need to remember inserted * tuples (including new versions of updated tuples), so that we can flush * them from the caches if we abort the transaction. Similarly, we'd better * be able to flush "negative" cache entries that may have been loaded in * place of deleted tuples, so we still need the deleted ones too. * * If we successfully complete the transaction, we have to broadcast all * these invalidation events to other backends (via the SI message queue) * so that they can flush obsolete entries from their caches. Note we have * to record the transaction commit before sending SI messages, otherwise * the other backends won't see our updated tuples as good. * * In short, we need to remember until xact end every insert or delete * of a tuple that might be in the system caches. Updates are treated as * two events, delete + insert, for simplicity. (There are cases where * it'd be possible to record just one event, but we don't currently try.) * * We do not need to register EVERY tuple operation in this way, just those * on tuples in relations that have associated catcaches. We do, however, * have to register every operation on every tuple that *could* be in a * catcache, whether or not it currently is in our cache. Also, if the * tuple is in a relation that has multiple catcaches, we need to register * an invalidation message for each such catcache. catcache.c's * PrepareToInvalidateCacheTuple() routine provides the knowledge of which * catcaches may need invalidation for a given tuple. * * Also, whenever we see an operation on a pg_class or pg_attribute tuple, * we register a relcache flush operation for the relation described by that * tuple. * * We keep the relcache flush requests in lists separate from the catcache * tuple flush requests. This allows us to issue all the pending catcache * flushes before we issue relcache flushes, which saves us from loading * a catcache tuple during relcache load only to flush it again right away. * Also, we avoid queuing multiple relcache flush requests for the same * relation, since a relcache flush is relatively expensive to do. * (XXX is it worth testing likewise for duplicate catcache flush entries? * Probably not.) * * If a relcache flush is issued for a system relation that we preload * from the relcache init file, we must also delete the init file so that * it will be rebuilt during the next backend restart. The actual work of * manipulating the init file is in relcache.c, but we keep track of the * need for it here. * * All the request lists are kept in TopTransactionContext memory, since * they need not live beyond the end of the current transaction. * * * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION * $Header: /cvsroot/pgsql/src/backend/utils/cache/inval.c,v 1.55 2002/09/04 20:31:29 momjian Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "catalog/catalog.h" #include "miscadmin.h" #include "storage/sinval.h" #include "utils/catcache.h" #include "utils/inval.h" #include "utils/memutils.h" #include "utils/relcache.h" /* * To minimize palloc traffic, we keep pending requests in successively- * larger chunks (a slightly more sophisticated version of an expansible * array). All request types can be stored as SharedInvalidationMessage * records. */ typedef struct InvalidationChunk { struct InvalidationChunk *next; /* list link */ int nitems; /* # items currently stored in chunk */ int maxitems; /* size of allocated array in this chunk */ SharedInvalidationMessage msgs[1]; /* VARIABLE LENGTH ARRAY */ } InvalidationChunk; /* VARIABLE LENGTH STRUCTURE */ typedef struct InvalidationListHeader { InvalidationChunk *cclist; /* list of chunks holding catcache msgs */ InvalidationChunk *rclist; /* list of chunks holding relcache msgs */ } InvalidationListHeader; /*---------------- * Invalidation info is divided into two lists: * 1) events so far in current command, not yet reflected to caches. * 2) events in previous commands of current transaction; these have * been reflected to local caches, and must be either broadcast to * other backends or rolled back from local cache when we commit * or abort the transaction. * * The relcache-file-invalidated flag can just be a simple boolean, * since we only act on it at transaction commit; we don't care which * command of the transaction set it. *---------------- */ /* head of current-command event list */ static InvalidationListHeader CurrentCmdInvalidMsgs; /* head of previous-commands event list */ static InvalidationListHeader PriorCmdInvalidMsgs; static bool RelcacheInitFileInval; /* init file must be invalidated? */ /* * Dynamically-registered callback functions. Current implementation * assumes there won't be very many of these at once; could improve if needed. */ #define MAX_CACHE_CALLBACKS 20 static struct CACHECALLBACK { int16 id; /* cache number or SHAREDINVALRELCACHE_ID */ CacheCallbackFunction function; Datum arg; } cache_callback_list[MAX_CACHE_CALLBACKS]; static int cache_callback_count = 0; /* ---------------------------------------------------------------- * Invalidation list support functions * * These three routines encapsulate processing of the "chunked" * representation of what is logically just a list of messages. * ---------------------------------------------------------------- */ /* * AddInvalidationMessage * Add an invalidation message to a list (of chunks). * * Note that we do not pay any great attention to maintaining the original * ordering of the messages. */ static void AddInvalidationMessage(InvalidationChunk **listHdr, SharedInvalidationMessage *msg) { InvalidationChunk *chunk = *listHdr; if (chunk == NULL) { /* First time through; create initial chunk */ #define FIRSTCHUNKSIZE 16 chunk = (InvalidationChunk *) MemoryContextAlloc(TopTransactionContext, sizeof(InvalidationChunk) + (FIRSTCHUNKSIZE - 1) *sizeof(SharedInvalidationMessage)); chunk->nitems = 0; chunk->maxitems = FIRSTCHUNKSIZE; chunk->next = *listHdr; *listHdr = chunk; } else if (chunk->nitems >= chunk->maxitems) { /* Need another chunk; double size of last chunk */ int chunksize = 2 * chunk->maxitems; chunk = (InvalidationChunk *) MemoryContextAlloc(TopTransactionContext, sizeof(InvalidationChunk) + (chunksize - 1) *sizeof(SharedInvalidationMessage)); chunk->nitems = 0; chunk->maxitems = chunksize; chunk->next = *listHdr; *listHdr = chunk; } /* Okay, add message to current chunk */ chunk->msgs[chunk->nitems] = *msg; chunk->nitems++; } /* * Free a list of inval message chunks. * * NOTE: when we are about to commit or abort a transaction, it's * not really necessary to pfree the lists explicitly, since they will * go away anyway when TopTransactionContext is destroyed. */ static void FreeInvalidationMessageList(InvalidationChunk **listHdr) { InvalidationChunk *chunk = *listHdr; *listHdr = NULL; while (chunk != NULL) { InvalidationChunk *nextchunk = chunk->next; pfree(chunk); chunk = nextchunk; } } /* * Append one list of invalidation message chunks to another, resetting * the source chunk-list pointer to NULL. */ static void AppendInvalidationMessageList(InvalidationChunk **destHdr, InvalidationChunk **srcHdr) { InvalidationChunk *chunk = *srcHdr; if (chunk == NULL) return; /* nothing to do */ while (chunk->next != NULL) chunk = chunk->next; chunk->next = *destHdr; *destHdr = *srcHdr; *srcHdr = NULL; } /* * Process a list of invalidation messages. * * This is a macro that executes the given code fragment for each message in * a message chunk list. The fragment should refer to the message as *msg. */ #define ProcessMessageList(listHdr, codeFragment) \ do { \ InvalidationChunk *_chunk; \ for (_chunk = (listHdr); _chunk != NULL; _chunk = _chunk->next) \ { \ int _cindex; \ for (_cindex = 0; _cindex < _chunk->nitems; _cindex++) \ { \ SharedInvalidationMessage *msg = &_chunk->msgs[_cindex]; \ codeFragment; \ } \ } \ } while (0) /* ---------------------------------------------------------------- * Invalidation set support functions * * These routines understand about the division of a logical invalidation * list into separate physical lists for catcache and relcache entries. * ---------------------------------------------------------------- */ /* * Add a catcache inval entry */ static void AddCatcacheInvalidationMessage(InvalidationListHeader *hdr, int id, uint32 hashValue, ItemPointer tuplePtr, Oid dbId) { SharedInvalidationMessage msg; msg.cc.id = (int16) id; msg.cc.tuplePtr = *tuplePtr; msg.cc.dbId = dbId; msg.cc.hashValue = hashValue; AddInvalidationMessage(&hdr->cclist, &msg); } /* * Add a relcache inval entry */ static void AddRelcacheInvalidationMessage(InvalidationListHeader *hdr, Oid dbId, Oid relId) { SharedInvalidationMessage msg; /* Don't add a duplicate item */ /* We assume comparing relId is sufficient, needn't check dbId */ ProcessMessageList(hdr->rclist, if (msg->rc.relId == relId) return); /* OK, add the item */ msg.rc.id = SHAREDINVALRELCACHE_ID; msg.rc.dbId = dbId; msg.rc.relId = relId; AddInvalidationMessage(&hdr->rclist, &msg); } /* * Append one list of invalidation messages to another, resetting * the source list to empty. */ static void AppendInvalidationMessages(InvalidationListHeader *dest, InvalidationListHeader *src) { AppendInvalidationMessageList(&dest->cclist, &src->cclist); AppendInvalidationMessageList(&dest->rclist, &src->rclist); } /* * Reset an invalidation list to empty * * physicalFree may be set false if caller knows transaction is ending */ static void DiscardInvalidationMessages(InvalidationListHeader *hdr, bool physicalFree) { if (physicalFree) { /* Physically pfree the list data */ FreeInvalidationMessageList(&hdr->cclist); FreeInvalidationMessageList(&hdr->rclist); } else { /* * Assume the storage will go away at xact end, just reset * pointers */ hdr->cclist = NULL; hdr->rclist = NULL; } } /* * Execute the given function for all the messages in an invalidation list. * The list is not altered. * * catcache entries are processed first, for reasons mentioned above. */ static void ProcessInvalidationMessages(InvalidationListHeader *hdr, void (*func) (SharedInvalidationMessage *msg)) { ProcessMessageList(hdr->cclist, func(msg)); ProcessMessageList(hdr->rclist, func(msg)); } /* ---------------------------------------------------------------- * private support functions * ---------------------------------------------------------------- */ /* * RegisterCatcacheInvalidation * * Register an invalidation event for a catcache tuple entry. */ static void RegisterCatcacheInvalidation(int cacheId, uint32 hashValue, ItemPointer tuplePtr, Oid dbId) { AddCatcacheInvalidationMessage(&CurrentCmdInvalidMsgs, cacheId, hashValue, tuplePtr, dbId); } /* * RegisterRelcacheInvalidation * * As above, but register a relcache invalidation event. */ static void RegisterRelcacheInvalidation(Oid dbId, Oid relId) { AddRelcacheInvalidationMessage(&CurrentCmdInvalidMsgs, dbId, relId); /* * If the relation being invalidated is one of those cached in the * relcache init file, mark that we need to zap that file at commit. */ if (RelationIdIsInInitFile(relId)) RelcacheInitFileInval = true; } /* * LocalExecuteInvalidationMessage * * Process a single invalidation message (which could be either type). * Only the local caches are flushed; this does not transmit the message * to other backends. */ static void LocalExecuteInvalidationMessage(SharedInvalidationMessage *msg) { int i; if (msg->id >= 0) { if (msg->cc.dbId == MyDatabaseId || msg->cc.dbId == 0) { CatalogCacheIdInvalidate(msg->cc.id, msg->cc.hashValue, &msg->cc.tuplePtr); for (i = 0; i < cache_callback_count; i++) { struct CACHECALLBACK *ccitem = cache_callback_list + i; if (ccitem->id == msg->cc.id) (*ccitem->function) (ccitem->arg, InvalidOid); } } } else if (msg->id == SHAREDINVALRELCACHE_ID) { if (msg->rc.dbId == MyDatabaseId || msg->rc.dbId == 0) { RelationIdInvalidateRelationCacheByRelationId(msg->rc.relId); for (i = 0; i < cache_callback_count; i++) { struct CACHECALLBACK *ccitem = cache_callback_list + i; if (ccitem->id == SHAREDINVALRELCACHE_ID) (*ccitem->function) (ccitem->arg, msg->rc.relId); } } } else { elog(FATAL, "ExecuteInvalidationMessage: bogus message id %d", msg->id); } } /* * InvalidateSystemCaches * * This blows away all tuples in the system catalog caches and * all the cached relation descriptors (and closes their files too). * Relation descriptors that have positive refcounts are then rebuilt. * * We call this when we see a shared-inval-queue overflow signal, * since that tells us we've lost some shared-inval messages and hence * don't know what needs to be invalidated. */ static void InvalidateSystemCaches(void) { int i; ResetCatalogCaches(); RelationCacheInvalidate(); for (i = 0; i < cache_callback_count; i++) { struct CACHECALLBACK *ccitem = cache_callback_list + i; (*ccitem->function) (ccitem->arg, InvalidOid); } } /* * PrepareForTupleInvalidation * Detect whether invalidation of this tuple implies invalidation * of catalog/relation cache entries; if so, register inval events. */ static void PrepareForTupleInvalidation(Relation relation, HeapTuple tuple, void (*CacheIdRegisterFunc) (int, uint32, ItemPointer, Oid), void (*RelationIdRegisterFunc) (Oid, Oid)) { Oid tupleRelId; Oid relationId; if (IsBootstrapProcessingMode()) return; /* * We only need to worry about invalidation for tuples that are in * system relations; user-relation tuples are never in catcaches and * can't affect the relcache either. */ if (!IsSystemRelation(relation)) return; /* * TOAST tuples can likewise be ignored here. Note that TOAST tables * are considered system relations so they are not filtered by the * above test. */ if (IsToastRelation(relation)) return; /* * First let the catcache do its thing */ PrepareToInvalidateCacheTuple(relation, tuple, CacheIdRegisterFunc); /* * Now, is this tuple one of the primary definers of a relcache entry? */ tupleRelId = RelationGetRelid(relation); if (tupleRelId == RelOid_pg_class) relationId = HeapTupleGetOid(tuple); else if (tupleRelId == RelOid_pg_attribute) relationId = ((Form_pg_attribute) GETSTRUCT(tuple))->attrelid; else return; /* * Yes. We need to register a relcache invalidation event for the * relation identified by relationId. * * KLUGE ALERT: we always send the relcache event with MyDatabaseId, even * if the rel in question is shared. This essentially means that only * backends in this same database will react to the relcache flush * request. This is in fact appropriate, since only those backends * could see our pg_class or pg_attribute change anyway. It looks a * bit ugly though. */ (*RelationIdRegisterFunc) (MyDatabaseId, relationId); } /* ---------------------------------------------------------------- * public functions * ---------------------------------------------------------------- */ /* * AcceptInvalidationMessages * Read and process invalidation messages from the shared invalidation * message queue. * * Note: * This should be called as the first step in processing a transaction. */ void AcceptInvalidationMessages(void) { ReceiveSharedInvalidMessages(LocalExecuteInvalidationMessage, InvalidateSystemCaches); } /* * AtEOXactInvalidationMessages * Process queued-up invalidation messages at end of transaction. * * If isCommit, we must send out the messages in our PriorCmdInvalidMsgs list * to the shared invalidation message queue. Note that these will be read * not only by other backends, but also by our own backend at the next * transaction start (via AcceptInvalidationMessages). This means that * we can skip immediate local processing of anything that's still in * CurrentCmdInvalidMsgs, and just send that list out too. * * If not isCommit, we are aborting, and must locally process the messages * in PriorCmdInvalidMsgs. No messages need be sent to other backends, * since they'll not have seen our changed tuples anyway. We can forget * about CurrentCmdInvalidMsgs too, since those changes haven't touched * the caches yet. * * In any case, reset the various lists to empty. We need not physically * free memory here, since TopTransactionContext is about to be emptied * anyway. * * Note: * This should be called as the last step in processing a transaction. */ void AtEOXactInvalidationMessages(bool isCommit) { if (isCommit) { /* * Relcache init file invalidation requires processing both before * and after we send the SI messages. However, we need not do * anything unless we committed. */ if (RelcacheInitFileInval) RelationCacheInitFileInvalidate(true); AppendInvalidationMessages(&PriorCmdInvalidMsgs, &CurrentCmdInvalidMsgs); ProcessInvalidationMessages(&PriorCmdInvalidMsgs, SendSharedInvalidMessage); if (RelcacheInitFileInval) RelationCacheInitFileInvalidate(false); } else { ProcessInvalidationMessages(&PriorCmdInvalidMsgs, LocalExecuteInvalidationMessage); } RelcacheInitFileInval = false; DiscardInvalidationMessages(&PriorCmdInvalidMsgs, false); DiscardInvalidationMessages(&CurrentCmdInvalidMsgs, false); } /* * CommandEndInvalidationMessages * Process queued-up invalidation messages at end of one command * in a transaction. * * Here, we send no messages to the shared queue, since we don't know yet if * we will commit. We do need to locally process the CurrentCmdInvalidMsgs * list, so as to flush our caches of any entries we have outdated in the * current command. We then move the current-cmd list over to become part * of the prior-cmds list. * * The isCommit = false case is not currently used, but may someday be * needed to support rollback to a savepoint within a transaction. * * Note: * This should be called during CommandCounterIncrement(), * after we have advanced the command ID. */ void CommandEndInvalidationMessages(bool isCommit) { if (isCommit) { ProcessInvalidationMessages(&CurrentCmdInvalidMsgs, LocalExecuteInvalidationMessage); AppendInvalidationMessages(&PriorCmdInvalidMsgs, &CurrentCmdInvalidMsgs); } else { /* XXX what needs to be done here? */ } } /* * CacheInvalidateHeapTuple * Register the given tuple for invalidation at end of command * (ie, current command is outdating this tuple). */ void CacheInvalidateHeapTuple(Relation relation, HeapTuple tuple) { PrepareForTupleInvalidation(relation, tuple, RegisterCatcacheInvalidation, RegisterRelcacheInvalidation); } /* * CacheInvalidateRelcache * Register invalidation of the specified relation's relcache entry * at end of command. * * This is used in places that need to force relcache rebuild but aren't * changing any of the tuples recognized as contributors to the relcache * entry by PrepareForTupleInvalidation. (An example is dropping an index.) */ void CacheInvalidateRelcache(Oid relationId) { /* See KLUGE ALERT in PrepareForTupleInvalidation */ RegisterRelcacheInvalidation(MyDatabaseId, relationId); } /* * CacheRegisterSyscacheCallback * Register the specified function to be called for all future * invalidation events in the specified cache. * * NOTE: currently, the OID argument to the callback routine is not * provided for syscache callbacks; the routine doesn't really get any * useful info as to exactly what changed. It should treat every call * as a "cache flush" request. */ void CacheRegisterSyscacheCallback(int cacheid, CacheCallbackFunction func, Datum arg) { if (cache_callback_count >= MAX_CACHE_CALLBACKS) elog(FATAL, "Out of cache_callback_list slots"); cache_callback_list[cache_callback_count].id = cacheid; cache_callback_list[cache_callback_count].function = func; cache_callback_list[cache_callback_count].arg = arg; ++cache_callback_count; } /* * CacheRegisterRelcacheCallback * Register the specified function to be called for all future * relcache invalidation events. The OID of the relation being * invalidated will be passed to the function. * * NOTE: InvalidOid will be passed if a cache reset request is received. * In this case the called routines should flush all cached state. */ void CacheRegisterRelcacheCallback(CacheCallbackFunction func, Datum arg) { if (cache_callback_count >= MAX_CACHE_CALLBACKS) elog(FATAL, "Out of cache_callback_list slots"); cache_callback_list[cache_callback_count].id = SHAREDINVALRELCACHE_ID; cache_callback_list[cache_callback_count].function = func; cache_callback_list[cache_callback_count].arg = arg; ++cache_callback_count; }