lockid_t Class Reference

List of all members.

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Detailed Description

The means of identifying a desired or held lock.

Lock manager requests (acquire, release, query) take an argument of this kind to identify the entity to be locked. Not all lockids refer to anything extant.

The structure of the lockid_t is such that several entity types are inferred, and the lockid_t has constructors from these entities' identifier classes, as well as methods to modify the lockid while retaining its inferred-entity type. The enumerator type name_space_t identifies the entity type of the lock_id, and is returned by the method space:

• t_vol :
  • volume lock
  • no parent in hierarchy
  • constructed from vid_t
  • can extract vid_t with vid()

• t_store :
  • store lock (file lock, index lock)
  • parent in hierarchy is volume lock
  • constructed from stid_t
  • can extract snum_t with store() and vid_t with vid()
  • can extract stid with extract_stid()

• t_page :
  • page lock
  • parent in hierarchy is store lock
  • constructed from lpid_t
  • can extract shpid_t with page(), snum_t with store() and vid_t with vid()
  • can extract stid with extract_stid()
  • can extract lpid with extract_lpid()

• t_kvl :
  • key-value lock
  • parent in hierarchy is store lock
  • constructed from kvl_t (which is constructed from a vec_t : see vec_t::make_kvl)
  • can extract kvl_t with extract_kvl()
  • can extract snum_t with store() and vid_t with vid()
  • can extract stid with extract_stid()

• t_record :
  • lock on record in file
  • parent in hierarchy is page lock
  • constructed from rid_t
  • can extract slotid_t with slot(), shpid_t with page(), snum_t with store() and vid_t with vid()
  • can extract rid_t with extract_rid()
  • can extract stid with extract_stid()
  • can extract lpid with extract_lpid()

• t_extent :
  • lock on extent
  • not in a hierarchy
  • constructed from extid_t
  • can extract extnum_t with extent()
  • can extract extid_t with extract_extent()

• t_user1 :
  • lock on user-defined entity 1
  • not in a hierarchy
  • constructed from user1_t
  • can extract user1_t with extract_user1()

• t_user2 :
  • lock on user-defined entity 2
  • parent in hierarchy is user-defined entity 1
  • constructed from user2_t
  • can extract user2_t with extract_user2()
  • can extract user1_t with extract_user1()

• t_user3 :
  • lock on user-defined entity 3
  • parent in hierarchy is user-defined entity 2
  • constructed from user3_t
  • can extract user3_t with extract_user3()
  • can extract user2_t with extract_user2()
  • can extract user1_t with extract_user1()

• t_user4 :
  • lock on user-defined entity 4
  • parent in hierarchy is user-defined entity 3
  • constructed from user4_t
  • can extract user4_t with extract_user4()
  • can extract user3_t with extract_user3()
  • can extract user2_t with extract_user2()
  • can extract user1_t with extract_user1()

Attention:

The enumeration values of name_space_t have functional significance; they are use to compute parents in the hierarchy, so modify them with care!

The user-defined entity types are for use by a server; they offer a hierarchy.

Examples:

lockid_test.cpp.

Definition at line 213 of file lock_s.h.

Public Types
typedef uint4_t	page_bits_t
enum	name_space_t
enum
enum
Public Member Functions
bool	operator< (lockid_t const &p) const
	comparison operator for lockid_t, used by lock manager
bool	operator== (const lockid_t &p) const
	equality operator for lockid_t
bool	operator!= (const lockid_t &p) const
	inequality operator for lockid_t
uint4_t	hash () const
	Used by lock cache.
void	zero ()
	clear out the lockid - initialize to mean nothing
name_space_t	lspace () const
	return the kind of entity this describes
vid_t	vid () const
	extract volume id lockid whose lspace() == t_vol or has parent with lspace() == t_vol
const snum_t &	store () const
	extract store number lockid whose lspace() == t_store or has parent with lspace() == t_store
const extnum_t &	extent () const
	extract extent number lockid whose lspace() == t_extent
const shpid_t &	page () const
	extract short page number lockid whose lspace() == t_page or has parent with lspace()==t_page
slotid_t	slot () const
	extract slot number lockid whose lspace() == t_record
uint2_t	u1 () const
	extract uint2_t from whose lspace() == t_user1
uint4_t	u2 () const
	extract uint4_t from whose lspace() == t_user2
uint4_t	u3 () const
	extract uint4_t from whose lspace() == t_user3
uint4_t	u4 () const
	extract uint4_t from whose lspace() == t_user4
void	set_ext_has_page_alloc (bool value)
	for extent locks only, used by volume manager
bool	ext_has_page_alloc () const
	for extent locks only, used by lock manager
NORET	lockid_t (const vid_t &vid)
	construct from volume id
NORET	lockid_t (const extid_t &extid)
	construct from full extent id
NORET	lockid_t (const stid_t &stid)
	construct from full store id
NORET	lockid_t (const lpid_t &lpid)
	construct from full page id
NORET	lockid_t (const rid_t &rid)
	construct from full record id
NORET	lockid_t (const kvl_t &kvl)
	construct from kvl_t (hash of key,value, from vec_t)
NORET	lockid_t (const lockid_t &i)
	copy constructor
NORET	lockid_t (const user1_t &u)
	construct from user1_t
NORET	lockid_t (const user2_t &u)
	construct from user2_t
NORET	lockid_t (const user3_t &u)
	construct from user3_t
NORET	lockid_t (const user4_t &u)
	construct from user4_t
void	extract_extent (extid_t &e) const
	extract a full extent id from an extent lock
void	extract_stid (stid_t &s) const
	extract a full store id from a store, page, or record lock
void	extract_lpid (lpid_t &p) const
	extract a full page id from a page or record lock
void	extract_rid (rid_t &r) const
	extract a full record id from a record lock
void	extract_kvl (kvl_t &k) const
	extract a kvl_t (hash of key,value) from a key-value lock
void	extract_user1 (user1_t &u) const
	extract a user1_t from user-defined entity 1, 2, 3, or 4
void	extract_user2 (user2_t &u) const
	extract a user2_t from user-defined entity 2, 3, or 4
void	extract_user3 (user3_t &u) const
	extract a user3_t from user-defined entity 3 or 4
void	extract_user4 (user4_t &u) const
	extract a user3_t from user-defined entity 4
bool	is_user_lock () const
	Return true if type is t_user1, t_user2, t_user3 or t_user4.
w_rc_t	truncate (name_space_t space)
	Nullify all parts of the lockid that apply to children in the hierarchy.
lockid_t &	operator= (const lockid_t &i)
	copy operator
Static Public Attributes
static const int	cached_granularity = t_page
Classes
struct	user1_t
	User-defined entity 1. More...
struct	user2_t
	User-defined entity 2. More...
struct	user3_t
	User-defined entity 3. More...
struct	user4_t
	User-defined entity 4. More...

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Member Function Documentation

void lockid_t::set_ext_has_page_alloc

(

bool

value

)

for extent locks only, used by volume manager

Set to true when the extent contains an uncommitted allocated page. This is done when a page is allocated in the extent; it is used for special handling of extent locks in the lock manager.

The special handling requires a little background:

• extent locks are not in the hierarchy
• extent IX locks are acquired when a page in the extent is allocated (or recovered, in recovery case)
• extent IX locks are acquired when a page in the extent is freed
• extent IX locks are acquired when allocating the extent to a store
• extent EX locks are acquired when deallocating all the extents in a store (destroying the store), at which time we have an EX lock on the store.

• We need some way to tell when an extent can be freed. It can be freed when there are no pages allocated in the extent. Presumably we would have any transaction that deallocated a page in the extent try to deallocate the extent (i.e., if there are no more pages in the extent). But it doesn't acquire an EX lock on the extent, so another transaction could slip in and allocate pages in the extent.
• If the transaction (that deleted one or more pages in an extent) tries to deallocate the extent at the transaction end, it would have to inspect the extent link to tell if the extent has no pages in it, and it would still have to do something to avoid races with other transactions.

The special handling is this:

• Transactions that allocate pages in an extent set the bit in the lock saying there are pages allocated in the extent.
• Transactions that deallocate pages in an extent clear the bit in the lock when there are no more pages allocated in the extent.
• This bypasses a page fix for inspecting the extlink_t.
• Synchronization for this bit in the lockid is provided by the volume manager; the bit is set and cleared only in the volume manager, which is a monitor.
• At transaction end, a transaction that has an IX lock on an extent tries to upgrade it to an EX if the extent lock indicates that no pages are allocated in the extent. If it succeeds, the lock manager can delete the extent while holding the EX lock, then free the lock.

When at the end of transaction, lock_m::release_duration() is called, the lock manager returns eFOUNDEXTTOFREE when it encounters an extent lock with this bit set.

bool lockid_t::ext_has_page_alloc

(

)

const

for extent locks only, used by lock manager

Returns true when the extent contains an uncommitted allocated page. See discussion in set_ext_has_page_alloc, above.

w_rc_t lockid_t::truncate

(

name_space_t

space

)

Nullify all parts of the lockid that apply to children in the hierarchy.

If the given space isn't in the hierarchy, this generates a fatal error.

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The documentation for this class was generated from the following file:

• src/sm/lock_s.h

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