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9c9936587c
only if at least N other backends currently have open transactions. This is not a great deal of intelligence about whether a delay might be profitable ... but it beats no intelligence at all. Note that the default COMMIT_DELAY is still zero --- this new code does nothing unless that setting is changed. Also, mark ENABLEFSYNC as a system-wide setting. It's no longer safe to allow that to be set per-backend, since we may be relying on some other backend's fsync to have synced the WAL log.
143 lines
4.4 KiB
C
143 lines
4.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* proc.h
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* per-process shared memory data structures
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*
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*
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* Portions Copyright (c) 1996-2001, 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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* $Id: proc.h,v 1.40 2001/02/26 00:50:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef _PROC_H_
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#define _PROC_H_
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#include "access/xlog.h"
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#include "storage/lock.h"
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/* configurable option */
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extern int DeadlockTimeout;
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typedef struct
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{
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IpcSemaphoreId semId; /* SysV semaphore set ID */
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int semNum; /* semaphore number within set */
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} SEMA;
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/*
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* Each backend has a PROC struct in shared memory. There is also a list of
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* currently-unused PROC structs that will be reallocated to new backends.
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*
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* links: list link for any list the PROC is in. When waiting for a lock,
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* the PROC is linked into that lock's waitProcs queue. A recycled PROC
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* is linked into ProcGlobal's freeProcs list.
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*/
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struct proc
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{
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/* proc->links MUST BE FIRST IN STRUCT (see ProcSleep,ProcWakeup,etc) */
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SHM_QUEUE links; /* list link if process is in a list */
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SEMA sem; /* ONE semaphore to sleep on */
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int errType; /* STATUS_OK or STATUS_ERROR after wakeup */
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TransactionId xid; /* transaction currently being executed by
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* this proc */
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TransactionId xmin; /* minimal running XID as it was when we
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* were starting our xact: vacuum must not
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* remove tuples deleted by xid >= xmin ! */
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/* XLOG location of first XLOG record written by this backend's current
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* transaction. If backend is not in a transaction or hasn't yet modified
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* anything, logRec.xrecoff is zero.
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*/
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XLogRecPtr logRec;
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/* Info about lock the process is currently waiting for, if any. */
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/* waitLock and waitHolder are NULL if not currently waiting. */
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LOCK *waitLock; /* Lock object we're sleeping on ... */
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HOLDER *waitHolder; /* Per-holder info for awaited lock */
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LOCKMODE waitLockMode; /* type of lock we're waiting for */
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LOCKMASK heldLocks; /* bitmask for lock types already held on
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* this lock object by this backend */
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int pid; /* This backend's process id */
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Oid databaseId; /* OID of database this backend is using */
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short sLocks[MAX_SPINS]; /* Spin lock stats */
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SHM_QUEUE procHolders; /* list of HOLDER objects for locks held or
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* awaited by this backend */
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};
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/* NOTE: "typedef struct proc PROC" appears in storage/lock.h. */
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extern PROC *MyProc;
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extern SPINLOCK ProcStructLock;
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#define PROC_INCR_SLOCK(lock) \
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do { \
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if (MyProc) (MyProc->sLocks[(lock)])++; \
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} while (0)
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#define PROC_DECR_SLOCK(lock) \
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do { \
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if (MyProc) (MyProc->sLocks[(lock)])--; \
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} while (0)
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/*
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* There is one ProcGlobal struct for the whole installation.
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*
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* PROC_NSEMS_PER_SET is the number of semaphores in each sys-V semaphore set
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* we allocate. It must be no more than 32 (or however many bits in an int
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* on your machine), or our free-semaphores bitmap won't work. It also must
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* be *less than* your kernel's SEMMSL (max semaphores per set) parameter,
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* which is often around 25. (Less than, because we allocate one extra sema
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* in each set for identification purposes.)
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*
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* PROC_SEM_MAP_ENTRIES is the number of semaphore sets we need to allocate
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* to keep track of up to MAXBACKENDS backends.
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*/
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#define PROC_NSEMS_PER_SET 16
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#define PROC_SEM_MAP_ENTRIES ((MAXBACKENDS-1)/PROC_NSEMS_PER_SET+1)
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typedef struct procglobal
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{
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/* Head of list of free PROC structures */
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SHMEM_OFFSET freeProcs;
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/* Info about semaphore sets used for per-process semaphores */
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IpcSemaphoreId procSemIds[PROC_SEM_MAP_ENTRIES];
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int32 freeSemMap[PROC_SEM_MAP_ENTRIES];
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/*
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* In each freeSemMap entry, bit i is set if the i'th semaphore of the
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* set is allocated to a process. (i counts from 0 at the LSB)
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*/
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} PROC_HDR;
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/*
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* Function Prototypes
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*/
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extern void InitProcGlobal(int maxBackends);
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extern void InitProcess(void);
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extern void ProcReleaseLocks(bool isCommit);
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extern bool ProcRemove(int pid);
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extern void ProcQueueInit(PROC_QUEUE *queue);
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extern int ProcSleep(LOCKMETHODTABLE *lockMethodTable, LOCKMODE lockmode,
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LOCK *lock, HOLDER *holder);
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extern PROC *ProcWakeup(PROC *proc, int errType);
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extern void ProcLockWakeup(LOCKMETHODTABLE *lockMethodTable, LOCK *lock);
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extern void ProcReleaseSpins(PROC *proc);
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extern bool LockWaitCancel(void);
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extern void HandleDeadLock(SIGNAL_ARGS);
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#endif /* PROC_H */
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