flatfiles.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

			 * rolvaliduntil is timestamptz, which we assume is double
			 * alignment and pass-by-reference.
			 */
			off = att_align(off, 'd');
			datum = PointerGetDatum(tp + off);
			auth_info[curr_role].rolvaliduntil = DatumGetCString(DirectFunctionCall1(timestamptz_out, datum));
		}

		/*
		 * Check for illegal characters in the user name and password.
		 */
		if (!name_okay(auth_info[curr_role].rolname))
		{
			ereport(LOG,
					(errmsg("invalid role name \"%s\"",
							auth_info[curr_role].rolname)));
			continue;
		}
		if (!name_okay(auth_info[curr_role].rolpassword))
		{
			ereport(LOG,
					(errmsg("invalid role password \"%s\"",
							auth_info[curr_role].rolpassword)));
			continue;
		}

		curr_role++;
		total_roles++;
	}
	heap_endscan(scan);

	/*
	 * Read pg_auth_members into temporary data structure, too
	 */
	totalblocks = RelationGetNumberOfBlocks(rel_authmem);
	totalblocks = totalblocks ? totalblocks : 1;
	est_rows = totalblocks * (BLCKSZ / (sizeof(HeapTupleHeaderData) + sizeof(FormData_pg_auth_members)));
	authmem_info = (authmem_entry *) palloc(est_rows * sizeof(authmem_entry));

	scan = heap_beginscan(rel_authmem, SnapshotNow, 0, NULL);
	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
	{
		Form_pg_auth_members memform = (Form_pg_auth_members) GETSTRUCT(tuple);

		if (curr_mem >= est_rows)
		{
			est_rows *= 2;
			authmem_info = (authmem_entry *)
				repalloc(authmem_info, est_rows * sizeof(authmem_entry));
		}

		authmem_info[curr_mem].roleid = memform->roleid;
		authmem_info[curr_mem].memberid = memform->member;
		curr_mem++;
		total_mem++;
	}
	heap_endscan(scan);

	/*
	 * Search for memberships.	We can skip all this if pg_auth_members is
	 * empty.
	 */
	if (total_mem > 0)
	{
		/*
		 * Sort auth_info by roleid and authmem_info by memberid.
		 */
		qsort(auth_info, total_roles, sizeof(auth_entry), oid_compar);
		qsort(authmem_info, total_mem, sizeof(authmem_entry), mem_compar);

		/*
		 * For each role, find what it belongs to.
		 */
		for (curr_role = 0; curr_role < total_roles; curr_role++)
		{
			List	   *roles_list;
			List	   *roles_names_list = NIL;
			ListCell   *mem;

			/* We can skip this for non-login roles */
			if (!auth_info[curr_role].rolcanlogin)
				continue;

			/*
			 * This search algorithm is the same as in is_member_of_role; we
			 * are just working with a different input data structure.
			 */
			roles_list = list_make1_oid(auth_info[curr_role].roleid);

			foreach(mem, roles_list)
			{
				authmem_entry key;
				authmem_entry *found_mem;
				int			first_found,
							last_found,
							i;

				key.memberid = lfirst_oid(mem);
				found_mem = bsearch(&key, authmem_info, total_mem,
									sizeof(authmem_entry), mem_compar);
				if (!found_mem)
					continue;

				/*
				 * bsearch found a match for us; but if there were multiple
				 * matches it could have found any one of them. Locate first
				 * and last match.
				 */
				first_found = last_found = (found_mem - authmem_info);
				while (first_found > 0 &&
					   mem_compar(&key, &authmem_info[first_found - 1]) == 0)
					first_found--;
				while (last_found + 1 < total_mem &&
					   mem_compar(&key, &authmem_info[last_found + 1]) == 0)
					last_found++;

				/*
				 * Now add all the new roles to roles_list.
				 */
				for (i = first_found; i <= last_found; i++)
					roles_list = list_append_unique_oid(roles_list,
													 authmem_info[i].roleid);
			}

			/*
			 * Convert list of role Oids to list of role names. We must do
			 * this before re-sorting auth_info.
			 *
			 * We skip the first list element (curr_role itself) since there
			 * is no point in writing that a role is a member of itself.
			 */
			for_each_cell(mem, lnext(list_head(roles_list)))
			{
				auth_entry	key_auth;
				auth_entry *found_role;

				key_auth.roleid = lfirst_oid(mem);
				found_role = bsearch(&key_auth, auth_info, total_roles,
									 sizeof(auth_entry), oid_compar);
				if (found_role) /* paranoia */
					roles_names_list = lappend(roles_names_list,
											   found_role->rolname);
			}
			auth_info[curr_role].member_of = roles_names_list;
			list_free(roles_list);
		}
	}

	/*
	 * Now sort auth_info into rolname order for output, and write the file.
	 */
	qsort(auth_info, total_roles, sizeof(auth_entry), name_compar);

	for (curr_role = 0; curr_role < total_roles; curr_role++)
	{
		auth_entry *arole = &auth_info[curr_role];

		if (arole->rolcanlogin)
		{
			ListCell   *mem;

			fputs_quote(arole->rolname, fp);
			fputs(" ", fp);
			fputs_quote(arole->rolpassword, fp);
			fputs(" ", fp);
			fputs_quote(arole->rolvaliduntil, fp);

			foreach(mem, arole->member_of)
			{
				fputs(" ", fp);
				fputs_quote((char *) lfirst(mem), fp);
			}

			fputs("\n", fp);
		}
	}

	if (FreeFile(fp))
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not write to temporary file \"%s\": %m",
						tempname)));

	/*
	 * Rename the temp file to its final name, deleting the old flat file. We
	 * expect that rename(2) is an atomic action.
	 */
	if (rename(tempname, filename))
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not rename file \"%s\" to \"%s\": %m",
						tempname, filename)));
}


/*
 * This routine is called once during database startup, after completing
 * WAL replay if needed.  Its purpose is to sync the flat files with the
 * current state of the database tables.  This is particularly important
 * during PITR operation, since the flat files will come from the
 * base backup which may be far out of sync with the current state.
 *
 * In theory we could skip rebuilding the flat files if no WAL replay
 * occurred, but it seems best to just do it always.  We have to
 * scan pg_database to compute the XID wrap limit anyway.  Also, this
 * policy means we need not force initdb to change the format of the
 * flat files.
 *
 * In a standalone backend we pass database_only = true to skip processing
 * the auth file.  We won't need it, and building it could fail if there's
 * something corrupt in the authid/authmem catalogs.
 */
void
BuildFlatFiles(bool database_only)
{
	ResourceOwner owner;
	RelFileNode rnode;
	Relation	rel_db,
				rel_authid,
				rel_authmem;

	/*
	 * We don't have any hope of running a real relcache, but we can use the
	 * same fake-relcache facility that WAL replay uses.
	 */
	XLogInitRelationCache();

	/* Need a resowner to keep the heapam and buffer code happy */
	owner = ResourceOwnerCreate(NULL, "BuildFlatFiles");
	CurrentResourceOwner = owner;

	/* hard-wired path to pg_database */
	rnode.spcNode = GLOBALTABLESPACE_OID;
	rnode.dbNode = 0;
	rnode.relNode = DatabaseRelationId;

	/* No locking is needed because no one else is alive yet */
	rel_db = XLogOpenRelation(rnode);
	write_database_file(rel_db);

	if (!database_only)
	{
		/* hard-wired path to pg_authid */
		rnode.spcNode = GLOBALTABLESPACE_OID;
		rnode.dbNode = 0;
		rnode.relNode = AuthIdRelationId;
		rel_authid = XLogOpenRelation(rnode);

		/* hard-wired path to pg_auth_members */
		rnode.spcNode = GLOBALTABLESPACE_OID;
		rnode.dbNode = 0;
		rnode.relNode = AuthMemRelationId;
		rel_authmem = XLogOpenRelation(rnode);

		write_auth_file(rel_authid, rel_authmem);
	}

	CurrentResourceOwner = NULL;
	ResourceOwnerDelete(owner);

	XLogCloseRelationCache();
}


/*
 * This routine is called during transaction commit or abort.
 *
 * On commit, if we've written any of the critical database tables during
 * the current transaction, update the flat files and signal the postmaster.
 *
 * On abort, just reset the static flags so we don't try to do it on the
 * next successful commit.
 *
 * NB: this should be the last step before actual transaction commit.
 * If any error aborts the transaction after we run this code, the postmaster
 * will still have received and cached the changed data; so minimize the
 * window for such problems.
 */
void
AtEOXact_UpdateFlatFiles(bool isCommit)
{
	Relation	drel = NULL;
	Relation	arel = NULL;
	Relation	mrel = NULL;

	if (database_file_update_subid == InvalidSubTransactionId &&
		auth_file_update_subid == InvalidSubTransactionId)
		return;					/* nothing to do */

	if (!isCommit)
	{
		database_file_update_subid = InvalidSubTransactionId;
		auth_file_update_subid = InvalidSubTransactionId;
		return;
	}

	/*
	 * Advance command counter to be certain we see all effects of the current
	 * transaction.
	 */
	CommandCounterIncrement();

	/*
	 * We use ExclusiveLock to ensure that only one backend writes the flat
	 * file(s) at a time.  That's sufficient because it's okay to allow plain
	 * reads of the tables in parallel.  There is some chance of a deadlock
	 * here (if we were triggered by a user update of one of the tables, which
	 * likely won't have gotten a strong enough lock), so get the locks we
	 * need before writing anything.
	 *
	 * For writing the auth file, it's sufficient to ExclusiveLock pg_authid;
	 * we take just regular AccessShareLock on pg_auth_members.
	 */
	if (database_file_update_subid != InvalidSubTransactionId)
		drel = heap_open(DatabaseRelationId, ExclusiveLock);

	if (auth_file_update_subid != InvalidSubTransactionId)
	{
		arel = heap_open(AuthIdRelationId, ExclusiveLock);
		mrel = heap_open(AuthMemRelationId, AccessShareLock);
	}

	/* Okay to write the files */
	if (database_file_update_subid != InvalidSubTransactionId)
	{
		database_file_update_subid = InvalidSubTransactionId;
		write_database_file(drel);
		heap_close(drel, NoLock);
	}

	if (auth_file_update_subid != InvalidSubTransactionId)
	{
		auth_file_update_subid = InvalidSubTransactionId;
		write_auth_file(arel, mrel);
		heap_close(arel, NoLock);
		heap_close(mrel, NoLock);
	}

	/*
	 * Signal the postmaster to reload its caches.
	 */
	SendPostmasterSignal(PMSIGNAL_PASSWORD_CHANGE);
}


/*
 * This routine is called during transaction prepare.
 *
 * Record which files need to be refreshed if this transaction later
 * commits.
 *
 * Note: it's OK to clear the flags immediately, since if the PREPARE fails
 * further on, we'd only reset the flags anyway. So there's no need for a
 * separate PostPrepare call.
 */
void
AtPrepare_UpdateFlatFiles(void)
{
	uint16		info = 0;

	if (database_file_update_subid != InvalidSubTransactionId)
	{
		database_file_update_subid = InvalidSubTransactionId;
		info |= FF_BIT_DATABASE;
	}
	if (auth_file_update_subid != InvalidSubTransactionId)
	{
		auth_file_update_subid = InvalidSubTransactionId;
		info |= FF_BIT_AUTH;
	}
	if (info != 0)
		RegisterTwoPhaseRecord(TWOPHASE_RM_FLATFILES_ID, info,
							   NULL, 0);
}


/*
 * AtEOSubXact_UpdateFlatFiles
 *
 * Called at subtransaction end, this routine resets or updates the
 * need-to-update-files flags.
 */
void
AtEOSubXact_UpdateFlatFiles(bool isCommit,
							SubTransactionId mySubid,
							SubTransactionId parentSubid)
{
	if (isCommit)
	{
		if (database_file_update_subid == mySubid)
			database_file_update_subid = parentSubid;

		if (auth_file_update_subid == mySubid)
			auth_file_update_subid = parentSubid;
	}
	else
	{
		if (database_file_update_subid == mySubid)
			database_file_update_subid = InvalidSubTransactionId;

		if (auth_file_update_subid == mySubid)
			auth_file_update_subid = InvalidSubTransactionId;
	}
}


/*
 * This trigger is fired whenever someone modifies pg_database, pg_authid
 * or pg_auth_members via general-purpose INSERT/UPDATE/DELETE commands.
 *
 * It is sufficient for this to be a STATEMENT trigger since we don't
 * care which individual rows changed.	It doesn't much matter whether
 * it's a BEFORE or AFTER trigger.
 */
Datum
flatfile_update_trigger(PG_FUNCTION_ARGS)
{
	TriggerData *trigdata = (TriggerData *) fcinfo->context;

	if (!CALLED_AS_TRIGGER(fcinfo))
		elog(ERROR,
			 "flatfile_update_trigger was not called by trigger manager");

	if (RelationGetNamespace(trigdata->tg_relation) != PG_CATALOG_NAMESPACE)
		elog(ERROR, "flatfile_update_trigger was called for wrong table");

	switch (RelationGetRelid(trigdata->tg_relation))
	{
		case DatabaseRelationId:
			database_file_update_needed();
			break;
		case AuthIdRelationId:
		case AuthMemRelationId:
			auth_file_update_needed();
			break;
		default:
			elog(ERROR, "flatfile_update_trigger was called for wrong table");
			break;
	}

	return PointerGetDatum(NULL);
}


/*
 * 2PC processing routine for COMMIT PREPARED case.
 *
 * (We don't have to do anything for ROLLBACK PREPARED.)
 */
void
flatfile_twophase_postcommit(TransactionId xid, uint16 info,
							 void *recdata, uint32 len)
{
	/*
	 * Set flags to do the needed file updates at the end of my own current
	 * transaction.  (XXX this has some issues if my own transaction later
	 * rolls back, or if there is any significant delay before I commit.  OK
	 * for now because we disallow COMMIT PREPARED inside a transaction
	 * block.)
	 */
	if (info & FF_BIT_DATABASE)
		database_file_update_needed();
	if (info & FF_BIT_AUTH)
		auth_file_update_needed();
}