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Simplify lock manager data structures by making a clear separation between
the data defining the semantics of a lock method (ie, conflict resolution table and ancillary data, which is all constant) and the hash tables storing the current state. The only thing we give up by this is the ability to use separate hashtables for different lock methods, but there is no need for that anyway. Put some extra fields into the LockMethod definition structs to clean up some other uglinesses, like hard-wired tests for DEFAULT_LOCKMETHOD and USER_LOCKMETHOD. This commit doesn't do anything about the performance issues we were discussing, but it clears away some of the underbrush that's in the way of fixing that.
This commit is contained in:
Tom Lane
@@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.91 2005/10/15 02:49:46 momjian Exp $
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* $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.92 2005/12/09 01:22:04 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@@ -55,50 +55,68 @@ typedef int LOCKMODE;
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#define LOCKBIT_ON(lockmode) (1 << (lockmode))
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#define LOCKBIT_OFF(lockmode) (~(1 << (lockmode)))
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/*
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* This data structure defines the locking semantics associated with a
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* "lock method". The semantics specify the meaning of each lock mode
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* (by defining which lock modes it conflicts with), and also whether locks
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* of this method are transactional (ie, are released at transaction end).
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* All of this data is constant and is kept in const tables.
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*
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* numLockModes -- number of lock modes (READ,WRITE,etc) that
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* are defined in this lock method. Must be less than MAX_LOCKMODES.
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*
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* transactional -- TRUE if locks are released automatically at xact end.
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*
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* conflictTab -- this is an array of bitmasks showing lock
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* mode conflicts. conflictTab[i] is a mask with the j-th bit
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* turned on if lock modes i and j conflict. Lock modes are
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* numbered 1..numLockModes; conflictTab[0] is unused.
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*
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* lockModeNames -- ID strings for debug printouts.
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*
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* trace_flag -- pointer to GUC trace flag for this lock method.
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*/
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typedef struct LockMethodData
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{
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int numLockModes;
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bool transactional;
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const LOCKMASK *conflictTab;
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const char * const *lockModeNames;
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const bool *trace_flag;
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} LockMethodData;
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typedef const LockMethodData *LockMethod;
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/*
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* There is normally only one lock method, the default one.
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* If user locks are enabled, an additional lock method is present.
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* Lock methods are identified by LOCKMETHODID. (Despite the declaration as
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* uint16, we are constrained to 256 lockmethods by the layout of LOCKTAG.)
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*/
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typedef uint16 LOCKMETHODID;
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/* MAX_LOCK_METHODS is the number of distinct lock control tables allowed */
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#define MAX_LOCK_METHODS 3
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#define INVALID_LOCKMETHOD 0
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/* These identify the known lock methods */
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#define DEFAULT_LOCKMETHOD 1
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#define USER_LOCKMETHOD 2
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#define LockMethodIsValid(lockmethodid) ((lockmethodid) != INVALID_LOCKMETHOD)
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extern int NumLockMethods;
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/*
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* This is the control structure for a lock table. It lives in shared
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* memory. Currently, none of these fields change after startup. In addition
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* to the LockMethodData, a lock table has a shared "lockHash" table holding
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* per-locked-object lock information, and a shared "proclockHash" table
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* holding per-lock-holder/waiter lock information.
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*
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* masterLock -- LWLock used to synchronize access to the table
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*
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* numLockModes -- number of lock types (READ,WRITE,etc) that
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* are defined on this lock table
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*
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* conflictTab -- this is an array of bitmasks showing lock
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* type conflicts. conflictTab[i] is a mask with the j-th bit
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* turned on if lock types i and j conflict.
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* These are the valid values of type LOCKMODE for all the standard lock
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* methods (both DEFAULT and USER).
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*/
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typedef struct LockMethodData
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{
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LWLockId masterLock;
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int numLockModes;
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LOCKMASK conflictTab[MAX_LOCKMODES];
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} LockMethodData;
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typedef LockMethodData *LockMethod;
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/* NoLock is not a lock mode, but a flag value meaning "don't get a lock" */
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#define NoLock 0
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#define AccessShareLock 1 /* SELECT */
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#define RowShareLock 2 /* SELECT FOR UPDATE/FOR SHARE */
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#define RowExclusiveLock 3 /* INSERT, UPDATE, DELETE */
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#define ShareUpdateExclusiveLock 4 /* VACUUM (non-FULL) */
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#define ShareLock 5 /* CREATE INDEX */
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#define ShareRowExclusiveLock 6 /* like EXCLUSIVE MODE, but allows ROW
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* SHARE */
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#define ExclusiveLock 7 /* blocks ROW SHARE/SELECT...FOR
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* UPDATE */
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#define AccessExclusiveLock 8 /* ALTER TABLE, DROP TABLE, VACUUM
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* FULL, and unqualified LOCK TABLE */
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/*
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@@ -138,9 +156,7 @@ typedef enum LockTagType
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* to widen Oid, BlockNumber, or TransactionId to more than 32 bits.
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*
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* We include lockmethodid in the locktag so that a single hash table in
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* shared memory can store locks of different lockmethods. For largely
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* historical reasons, it's passed to the lock.c routines as a separate
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* argument and then stored into the locktag.
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* shared memory can store locks of different lockmethods.
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*/
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typedef struct LOCKTAG
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{
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@@ -162,42 +178,48 @@ typedef struct LOCKTAG
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_RELATION)
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(locktag).locktag_type = LOCKTAG_RELATION, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_RELATION_EXTEND(locktag,dboid,reloid) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_RELATION_EXTEND)
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(locktag).locktag_type = LOCKTAG_RELATION_EXTEND, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_PAGE(locktag,dboid,reloid,blocknum) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = (blocknum), \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_PAGE)
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(locktag).locktag_type = LOCKTAG_PAGE, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_TUPLE(locktag,dboid,reloid,blocknum,offnum) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = (blocknum), \
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(locktag).locktag_field4 = (offnum), \
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(locktag).locktag_type = LOCKTAG_TUPLE)
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(locktag).locktag_type = LOCKTAG_TUPLE, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_TRANSACTION(locktag,xid) \
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((locktag).locktag_field1 = (xid), \
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(locktag).locktag_field2 = 0, \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_TRANSACTION)
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(locktag).locktag_type = LOCKTAG_TRANSACTION, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_OBJECT(locktag,dboid,classoid,objoid,objsubid) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (classoid), \
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(locktag).locktag_field3 = (objoid), \
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(locktag).locktag_field4 = (objsubid), \
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(locktag).locktag_type = LOCKTAG_OBJECT)
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(locktag).locktag_type = LOCKTAG_OBJECT, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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/*
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@@ -366,18 +388,13 @@ typedef enum
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* function prototypes
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*/
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extern void InitLocks(void);
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extern LockMethod GetLocksMethodTable(LOCK *lock);
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extern LOCKMETHODID LockMethodTableInit(const char *tabName,
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const LOCKMASK *conflictsP,
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int numModes);
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extern LOCKMETHODID LockMethodTableRename(LOCKMETHODID lockmethodid);
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extern LockAcquireResult LockAcquire(LOCKMETHODID lockmethodid,
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LOCKTAG *locktag,
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extern LockMethod GetLocksMethodTable(const LOCK *lock);
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extern LockAcquireResult LockAcquire(const LOCKTAG *locktag,
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bool isTempObject,
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LOCKMODE lockmode,
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bool sessionLock,
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bool dontWait);
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extern bool LockRelease(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
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extern bool LockRelease(const LOCKTAG *locktag,
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LOCKMODE lockmode, bool sessionLock);
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extern void LockReleaseAll(LOCKMETHODID lockmethodid, bool allLocks);
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extern void LockReleaseCurrentOwner(void);
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@@ -399,7 +416,7 @@ extern void RememberSimpleDeadLock(PGPROC *proc1,
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PGPROC *proc2);
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extern void InitDeadLockChecking(void);
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extern LockData *GetLockStatusData(void);
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extern const char *GetLockmodeName(LOCKMODE mode);
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extern const char *GetLockmodeName(LOCKMETHODID lockmethodid, LOCKMODE mode);
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extern void lock_twophase_recover(TransactionId xid, uint16 info,
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void *recdata, uint32 len);
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