portalmem.c

关系型数据库 Postgresql 6.5.2

{
	static bool processing = false;
	HASHCTL		ctl;

	AssertState(!processing);
	AssertArg(BoolIsValid(on));

	if (BypassEnable(&PortalManagerEnableCount, on))
		return;

	processing = true;

	if (on)
	{							/* initialize */
		EnableMemoryContext(true);

		PortalMemory = CreateGlobalMemory(PortalMemoryName);

		ctl.keysize = MAX_PORTALNAME_LEN;
		ctl.datasize = sizeof(Portal);

		/*
		 * use PORTALS_PER_USER, defined in utils/portal.h as a guess of
		 * how many hash table entries to create, initially
		 */
		PortalHashTable = hash_create(PORTALS_PER_USER * 3, &ctl, HASH_ELEM);

		CreateNewBlankPortal();

	}
	else
	{							/* cleanup */
		if (PortalIsValid(BlankPortal))
		{
			PortalDestroy(&BlankPortal);
			MemoryContextFree((MemoryContext) PortalMemory,
							  (Pointer) BlankPortal);
			BlankPortal = NULL;
		}

		/*
		 * Each portal must free its non-memory resources specially.
		 */
		HashTableWalk(PortalHashTable, PortalDestroy, 0);
		hash_destroy(PortalHashTable);
		PortalHashTable = NULL;

		GlobalMemoryDestroy(PortalMemory);
		PortalMemory = NULL;

		EnableMemoryContext(true);
	}

	processing = false;
}

/*
 * GetPortalByName
 *		Returns a portal given a portal name; returns blank portal given
 * NULL; returns invalid portal if portal not found.
 *
 * Exceptions:
 *		BadState if called when disabled.
 */
Portal
GetPortalByName(char *name)
{
	Portal		portal;

	AssertState(PortalManagerEnabled);

	if (PointerIsValid(name))
		PortalHashTableLookup(name, portal);
	else
	{
		if (!PortalIsValid(BlankPortal))
			CreateNewBlankPortal();
		portal = BlankPortal;
	}

	return portal;
}

/*
 * BlankPortalAssignName
 *		Returns former blank portal as portal with given name.
 *
 * Side effect:
 *		All references to the former blank portal become incorrect.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadState if called without an intervening call to GetPortalByName(NULL).
 *		BadArg if portal name is invalid.
 *		"WARN" if portal name is in use.
 */
Portal
BlankPortalAssignName(char *name)		/* XXX PortalName */
{
	Portal		portal;
	uint16		length;

	AssertState(PortalManagerEnabled);
	AssertState(PortalIsValid(BlankPortal));
	AssertArg(PointerIsValid(name));	/* XXX PortalName */

	portal = GetPortalByName(name);
	if (PortalIsValid(portal))
	{
		elog(NOTICE, "BlankPortalAssignName: portal %s already exists", name);
		return portal;
	}

	/*
	 * remove blank portal
	 */
	portal = BlankPortal;
	BlankPortal = NULL;

	/*
	 * initialize portal name
	 */
	length = 1 + strlen(name);
	portal->name = (char *)
		MemoryContextAlloc((MemoryContext) &portal->variable, length);

	strncpy(portal->name, name, length);

	/*
	 * put portal in table
	 */
	PortalHashTableInsert(portal);

	return portal;
}

/*
 * PortalSetQuery
 *		Attaches a "query" to portal.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if portal is invalid.
 *		BadArg if queryDesc is "invalid."
 *		BadArg if state is "invalid."
 */
void
PortalSetQuery(Portal portal,
			   QueryDesc *queryDesc,
			   TupleDesc attinfo,
			   EState *state,
			   void (*cleanup) (Portal portal))
{
	AssertState(PortalManagerEnabled);
	AssertArg(PortalIsValid(portal));
	AssertArg(IsA((Node *) state, EState));

	portal->queryDesc = queryDesc;
	portal->state = state;
	portal->attinfo = attinfo;
	portal->cleanup = cleanup;
}

/*
 * PortalGetQueryDesc
 *		Returns query attached to portal.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if portal is invalid.
 */
QueryDesc  *
PortalGetQueryDesc(Portal portal)
{
	AssertState(PortalManagerEnabled);
	AssertArg(PortalIsValid(portal));

	return portal->queryDesc;
}

/*
 * PortalGetState
 *		Returns state attached to portal.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if portal is invalid.
 */
EState *
PortalGetState(Portal portal)
{
	AssertState(PortalManagerEnabled);
	AssertArg(PortalIsValid(portal));

	return portal->state;
}

/*
 * CreatePortal
 *		Returns a new portal given a name.
 *
 * Note:
 *		This is expected to be of very limited usability.  See instead,
 * BlankPortalAssignName.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if portal name is invalid.
 *		"WARN" if portal name is in use.
 */
Portal
CreatePortal(char *name)		/* XXX PortalName */
{
	Portal		portal;
	uint16		length;

	AssertState(PortalManagerEnabled);
	AssertArg(PointerIsValid(name));	/* XXX PortalName */

	portal = GetPortalByName(name);
	if (PortalIsValid(portal))
	{
		elog(NOTICE, "CreatePortal: portal %s already exists", name);
		return portal;
	}

	/* make new portal structure */
	portal = (Portal)
		MemoryContextAlloc((MemoryContext) PortalMemory, sizeof *portal);

	/* initialize portal variable context */
	NodeSetTag((Node *) &portal->variable, T_PortalVariableMemory);
	AllocSetInit(&portal->variable.setData, DynamicAllocMode, (Size) 0);
	portal->variable.method = &PortalVariableContextMethodsData;

	/* initialize portal heap context */
	NodeSetTag((Node *) &portal->heap, T_PortalHeapMemory);
	portal->heap.block = NULL;
	FixedStackInit(&portal->heap.stackData,
				   offsetof(HeapMemoryBlockData, itemData));
	portal->heap.method = &PortalHeapContextMethodsData;

	/* initialize portal name */
	length = 1 + strlen(name);
	portal->name = (char *)
		MemoryContextAlloc((MemoryContext) &portal->variable, length);
	strncpy(portal->name, name, length);

	/* initialize portal query */
	portal->queryDesc = NULL;
	portal->attinfo = NULL;
	portal->state = NULL;
	portal->cleanup = NULL;

	/* put portal in table */
	PortalHashTableInsert(portal);

	/* Trap(PointerIsValid(name), Unimplemented); */
	return portal;
}

/*
 * PortalDestroy
 *		Destroys portal.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if portal is invalid.
 */
void
PortalDestroy(Portal *portalP)
{
	Portal		portal = *portalP;

	AssertState(PortalManagerEnabled);
	AssertArg(PortalIsValid(portal));

	/* remove portal from table if not blank portal */
	if (portal != BlankPortal)
		PortalHashTableDelete(portal);

	/* reset portal */
	if (PointerIsValid(portal->cleanup))
		(*portal->cleanup) (portal);

	PortalResetHeapMemory(portal);
	MemoryContextFree((MemoryContext) &portal->variable,
					  (Pointer) portal->name);
	AllocSetReset(&portal->variable.setData);	/* XXX log */

	/*
	 * In the case of a transaction abort it is possible that we get
	 * called while one of the memory contexts of the portal we're
	 * destroying is the current memory context.
	 *
	 * Don't know how to handle that cleanly because it is required to be in
	 * that context right now. This portal struct remains allocated in the
	 * PortalMemory context until backend dies.
	 *
	 * Not happy with that, but it's better to loose some bytes of memory
	 * than to have the backend dump core.
	 *
	 * --- Feb. 04, 1999 Jan Wieck
	 */
	if (CurrentMemoryContext == (MemoryContext) PortalGetHeapMemory(portal))
		return;
	if (CurrentMemoryContext == (MemoryContext) PortalGetVariableMemory(portal))
		return;

	if (portal != BlankPortal)
		MemoryContextFree((MemoryContext) PortalMemory, (Pointer) portal);
}

/* ----------------
 *		PortalResetHeapMemory
 *				Resets portal's heap memory context.
 *
 * Someday, Reset, Start, and End can be optimized by keeping a global
 * portal module stack of free HeapMemoryBlock's.  This will make Start
 * and End be fast.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadState if called when not in PortalHeapMemory context.
 *		BadArg if mode is invalid.
 * ----------------
 */
void
PortalResetHeapMemory(Portal portal)
{
	PortalHeapMemory context;
	MemoryContext currentContext;

	context = PortalGetHeapMemory(portal);

	if (PointerIsValid(context->block))
	{
		/* save present context */
		currentContext = MemoryContextSwitchTo((MemoryContext) context);

		do
		{
			EndPortalAllocMode();
		} while (PointerIsValid(context->block));

		/* restore context */
		MemoryContextSwitchTo(currentContext);
	}
}

/*
 * StartPortalAllocMode
 *		Starts a new block of portal heap allocation using mode and limit;
 *		the current block is disabled until EndPortalAllocMode is called.
 *
 * Note:
 *		Note blocks may be stacked and restored arbitarily.
 *		The semantics of mode and limit are described in aset.h.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadState if called when not in PortalHeapMemory context.
 *		BadArg if mode is invalid.
 */
void
StartPortalAllocMode(AllocMode mode, Size limit)
{
	PortalHeapMemory context;

	AssertState(PortalManagerEnabled);
	AssertState(IsA(CurrentMemoryContext, PortalHeapMemory));
	/* AssertArg(AllocModeIsValid); */

	context = (PortalHeapMemory) CurrentMemoryContext;

	/* stack current mode */
	if (PointerIsValid(context->block))
		FixedStackPush(&context->stackData, context->block);

	/* allocate and initialize new block */
	context->block = MemoryContextAlloc(
			  (MemoryContext) PortalHeapMemoryGetVariableMemory(context),
										sizeof(HeapMemoryBlockData));

	/* XXX careful, context->block has never been stacked => bad state */

	AllocSetInit(&HEAPMEMBLOCK(context)->setData, mode, limit);
}

/*
 * EndPortalAllocMode
 *		Ends current block of portal heap allocation; previous block is
 *		reenabled.
 *
 * Note:
 *		Note blocks may be stacked and restored arbitarily.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadState if called when not in PortalHeapMemory context.
 */
void
EndPortalAllocMode()
{
	PortalHeapMemory context;

	AssertState(PortalManagerEnabled);
	AssertState(IsA(CurrentMemoryContext, PortalHeapMemory));

	context = (PortalHeapMemory) CurrentMemoryContext;
	AssertState(PointerIsValid(context->block));		/* XXX Trap(...) */

	/* free current mode */
	AllocSetReset(&HEAPMEMBLOCK(context)->setData);
	MemoryContextFree((MemoryContext) PortalHeapMemoryGetVariableMemory(context),
					  context->block);

	/* restore previous mode */
	context->block = FixedStackPop(&context->stackData);
}

/*
 * PortalGetVariableMemory
 *		Returns variable memory context for a given portal.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if portal is invalid.
 */
PortalVariableMemory
PortalGetVariableMemory(Portal portal)
{
	return &portal->variable;
}

/*
 * PortalGetHeapMemory
 *		Returns heap memory context for a given portal.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if portal is invalid.
 */
PortalHeapMemory
PortalGetHeapMemory(Portal portal)
{
	return &portal->heap;
}

/*
 * PortalVariableMemoryGetPortal
 *		Returns portal containing given variable memory context.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if context is invalid.
 */
static Portal
PortalVariableMemoryGetPortal(PortalVariableMemory context)
{
	return (Portal) ((char *) context - offsetof(PortalD, variable));
}

/*
 * PortalHeapMemoryGetPortal
 *		Returns portal containing given heap memory context.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if context is invalid.
 */
static Portal
PortalHeapMemoryGetPortal(PortalHeapMemory context)
{
	return (Portal) ((char *) context - offsetof(PortalD, heap));
}

/*
 * PortalVariableMemoryGetHeapMemory
 *		Returns heap memory context associated with given variable memory.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if context is invalid.
 */
#ifdef NOT_USED
PortalHeapMemory
PortalVariableMemoryGetHeapMemory(PortalVariableMemory context)
{
	return ((PortalHeapMemory) ((char *) context
								- offsetof(PortalD, variable)
								+offsetof(PortalD, heap)));
}

#endif

/*
 * PortalHeapMemoryGetVariableMemory
 *		Returns variable memory context associated with given heap memory.
 *
 * Exceptions:
 *		BadState if called when disabled.
 *		BadArg if context is invalid.
 */
static PortalVariableMemory
PortalHeapMemoryGetVariableMemory(PortalHeapMemory context)
{
	return ((PortalVariableMemory) ((char *) context
									- offsetof(PortalD, heap)
									+offsetof(PortalD, variable)));
}