sinvaladt.c

关系型数据库 Postgresql 6.5.2

/*-------------------------------------------------------------------------
 *
 * sinvaladt.c
 *	  POSTGRES shared cache invalidation segment definitions.
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /usr/local/cvsroot/pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.20 1999/05/28 17:03:28 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <stdio.h>
#include <signal.h>
#include <unistd.h>

#include "postgres.h"

#include "storage/ipc.h"
#include "storage/backendid.h"
#include "storage/sinvaladt.h"
#include "storage/lmgr.h"
#include "utils/memutils.h"
#include "utils/palloc.h"
#include "utils/trace.h"

/* ----------------
 *		global variable notes
 *
 *		SharedInvalidationSemaphore
 *
 *		shmInvalBuffer
 *				the shared buffer segment, set by SISegmentAttach()
 *
 *		MyBackendId
 *				might be removed later, used only for
 *				debugging in debug routines (end of file)
 *
 *		SIDbId
 *				identification of buffer (disappears)
 *
 *		SIRelId			\
 *		SIDummyOid		 \	identification of buffer
 *		SIXidData		 /
 *		SIXid			/
 *
 *	XXX This file really needs to be cleaned up.  We switched to using
 *		spinlocks to protect critical sections (as opposed to using fake
 *		relations and going through the lock manager) and some of the old
 *		cruft was 'ifdef'ed out, while other parts (now unused) are still
 *		compiled into the system. -mer 5/24/92
 * ----------------
 */
#ifdef HAS_TEST_AND_SET
int			SharedInvalidationLockId;

#else
IpcSemaphoreId SharedInvalidationSemaphore;

#endif

SISeg	   *shmInvalBuffer;
extern BackendId MyBackendId;

static void CleanupInvalidationState(int status, SISeg *segInOutP);
static BackendId SIAssignBackendId(SISeg *segInOutP, BackendTag backendTag);
static int	SIGetNumEntries(SISeg *segP);

/************************************************************************/
/* SISetActiveProcess(segP, backendId)	set the backend status active	*/
/*		should be called only by the postmaster when creating a backend */
/************************************************************************/
/* XXX I suspect that the segP parameter is extraneous. -hirohama */
static void
SISetActiveProcess(SISeg *segInOutP, BackendId backendId)
{
	/* mark all messages as read */

	/* Assert(segP->procState[backendId - 1].tag == MyBackendTag); */

	segInOutP->procState[backendId - 1].resetState = false;
	segInOutP->procState[backendId - 1].limit = SIGetNumEntries(segInOutP);
}

/****************************************************************************/
/* SIBackendInit()	initializes a backend to operate on the buffer			*/
/****************************************************************************/
int
SIBackendInit(SISeg *segInOutP)
{
	LockRelId	LtCreateRelId();
	TransactionId LMITransactionIdCopy();

	Assert(MyBackendTag > 0);

	MyBackendId = SIAssignBackendId(segInOutP, MyBackendTag);
	if (MyBackendId == InvalidBackendTag)
		return 0;

#ifdef	INVALIDDEBUG
	elog(DEBUG, "SIBackendInit: backend tag %d; backend id %d.",
		 MyBackendTag, MyBackendId);
#endif	 /* INVALIDDEBUG */

	SISetActiveProcess(segInOutP, MyBackendId);
	on_shmem_exit(CleanupInvalidationState, (caddr_t) segInOutP);
	return 1;
}

/* ----------------
 *		SIAssignBackendId
 * ----------------
 */
static BackendId
SIAssignBackendId(SISeg *segInOutP, BackendTag backendTag)
{
	Index		index;
	ProcState  *stateP = NULL;

	for (index = 0; index < segInOutP->maxBackends; index++)
	{
		if (segInOutP->procState[index].tag == InvalidBackendTag ||
			segInOutP->procState[index].tag == backendTag)
		{
			stateP = &segInOutP->procState[index];
			break;
		}

		if (!PointerIsValid(stateP) ||
			(segInOutP->procState[index].resetState &&
			 (!stateP->resetState ||
			  stateP->tag < backendTag)) ||
			(!stateP->resetState &&
			 (segInOutP->procState[index].limit <
			  stateP->limit ||
			  stateP->tag < backendTag)))
			stateP = &segInOutP->procState[index];
	}

	/* verify that all "procState" entries checked for matching tags */

	for (index++; index < segInOutP->maxBackends; index++)
	{
		if (segInOutP->procState[index].tag == backendTag)
			elog(FATAL, "SIAssignBackendId: tag %d found twice", backendTag);
	}

	Assert(stateP);

	if (stateP->tag != InvalidBackendTag)
	{
		if (stateP->tag == backendTag)
			elog(NOTICE, "SIAssignBackendId: reusing tag %d", backendTag);
		else
		{
			elog(NOTICE, "SIAssignBackendId: discarding tag %d", stateP->tag);
			return InvalidBackendTag;
		}
	}

	stateP->tag = backendTag;

	return 1 + stateP - &segInOutP->procState[0];
}


/************************************************************************/
/* The following function should be called only by the postmaster !!	*/
/************************************************************************/

/************************************************************************/
/* SISetDeadProcess(segP, backendId)  set the backend status DEAD		*/
/*		should be called only by the postmaster when a backend died		*/
/************************************************************************/
static void
SISetDeadProcess(SISeg *segP, int backendId)
{
	/* XXX call me.... */

	segP->procState[backendId - 1].resetState = false;
	segP->procState[backendId - 1].limit = -1;
	segP->procState[backendId - 1].tag = InvalidBackendTag;
}

/*
 * CleanupInvalidationState
 * Note:
 *		This is a temporary hack.  ExitBackend should call this instead
 *		of exit (via on_shmem_exit).
 */
static void
CleanupInvalidationState(int status,	/* XXX */
						 SISeg *segInOutP)		/* XXX style */
{
	Assert(PointerIsValid(segInOutP));

	SISetDeadProcess(segInOutP, MyBackendId);
}


/************************************************************************/
/* SIComputeSize()	- compute size and offsets for SI segment			*/
/************************************************************************/
static void
SIComputeSize(SISegOffsets *oP, int maxBackends)
{
	int			A,
				B,
				a,
				b,
				totalSize;

	A = 0;
	/* sizeof(SISeg) includes the first ProcState entry */
	a = sizeof(SISeg) + sizeof(ProcState) * (maxBackends - 1);
	a = MAXALIGN(a);			/* offset to first data entry */
	b = sizeof(SISegEntry) * MAXNUMMESSAGES;
	B = A + a + b;
	B = MAXALIGN(B);
	totalSize = B - A;

	oP->startSegment = A;
	oP->offsetToFirstEntry = a; /* relative to A */
	oP->offsetToEndOfSegment = totalSize;		/* relative to A */
}


/************************************************************************/
/* SISetStartEntrySection(segP, offset)		- sets the offset			*/
/************************************************************************/
static void
SISetStartEntrySection(SISeg *segP, Offset offset)
{
	segP->startEntrySection = offset;
}

/************************************************************************/
/* SIGetStartEntrySection(segP)		- returnss the offset				*/
/************************************************************************/
static Offset
SIGetStartEntrySection(SISeg *segP)
{
	return segP->startEntrySection;
}


/************************************************************************/
/* SISetEndEntrySection(segP, offset)	- sets the offset				*/
/************************************************************************/
static void
SISetEndEntrySection(SISeg *segP, Offset offset)
{
	segP->endEntrySection = offset;
}

/************************************************************************/
/* SISetEndEntryChain(segP, offset)		- sets the offset				*/
/************************************************************************/
static void
SISetEndEntryChain(SISeg *segP, Offset offset)
{
	segP->endEntryChain = offset;
}

/************************************************************************/
/* SIGetEndEntryChain(segP)		- returnss the offset					*/
/************************************************************************/
static Offset
SIGetEndEntryChain(SISeg *segP)
{
	return segP->endEntryChain;
}

/************************************************************************/
/* SISetStartEntryChain(segP, offset)	- sets the offset				*/
/************************************************************************/
static void
SISetStartEntryChain(SISeg *segP, Offset offset)
{
	segP->startEntryChain = offset;
}

/************************************************************************/
/* SIGetStartEntryChain(segP)	- returns  the offset					*/
/************************************************************************/
static Offset
SIGetStartEntryChain(SISeg *segP)
{
	return segP->startEntryChain;
}

/************************************************************************/
/* SISetNumEntries(segP, num)	sets the current nuber of entries		*/
/************************************************************************/
static bool
SISetNumEntries(SISeg *segP, int num)
{
	if (num <= MAXNUMMESSAGES)
	{
		segP->numEntries = num;
		return true;
	}
	else
	{
		return false;			/* table full */
	}
}

/************************************************************************/
/* SIGetNumEntries(segP)	- returns the current nuber of entries		*/
/************************************************************************/
static int
SIGetNumEntries(SISeg *segP)
{
	return segP->numEntries;
}


/************************************************************************/
/* SISetMaxNumEntries(segP, num)	sets the maximal number of entries	*/
/************************************************************************/
static bool
SISetMaxNumEntries(SISeg *segP, int num)
{
	if (num <= MAXNUMMESSAGES)
	{
		segP->maxNumEntries = num;
		return true;
	}
	else
	{
		return false;			/* wrong number */
	}
}


/************************************************************************/
/* SIGetProcStateLimit(segP, i) returns the limit of read messages		*/
/************************************************************************/

#define SIGetProcStateLimit(segP,i) \
		((segP)->procState[i].limit)

/************************************************************************/
/* SIIncNumEntries(segP, num)	increments the current nuber of entries */
/************************************************************************/
static bool
SIIncNumEntries(SISeg *segP, int num)
{

	/*
	 * Try to prevent table overflow. When the table is 70% full send a
	 * SIGUSR2 to the postmaster which will send it back to all the
	 * backends. This will be handled by Async_NotifyHandler() with a
	 * StartTransactionCommand() which will flush unread SI entries for
	 * each backend.									dz - 27 Jan 1998
	 */
	if (segP->numEntries == (MAXNUMMESSAGES * 70 / 100))
	{
		TPRINTF(TRACE_VERBOSE,
			"SIIncNumEntries: table is 70%% full, signaling postmaster");
		kill(getppid(), SIGUSR2);
	}

	if ((segP->numEntries + num) <= MAXNUMMESSAGES)
	{
		segP->numEntries = segP->numEntries + num;
		return true;
	}
	else
	{
		return false;			/* table full */
	}
}

/************************************************************************/
/* SIDecNumEntries(segP, num)	decrements the current nuber of entries */
/************************************************************************/
static bool
SIDecNumEntries(SISeg *segP, int num)
{
	if ((segP->numEntries - num) >= 0)
	{
		segP->numEntries = segP->numEntries - num;
		return true;
	}
	else
	{
		return false;			/* not enough entries in table */
	}
}

/************************************************************************/
/* SISetStartFreeSpace(segP, offset)  - sets the offset					*/
/************************************************************************/
static void
SISetStartFreeSpace(SISeg *segP, Offset offset)
{
	segP->startFreeSpace = offset;
}

/************************************************************************/
/* SIGetStartFreeSpace(segP)  - returns the offset						*/
/************************************************************************/
static Offset
SIGetStartFreeSpace(SISeg *segP)
{
	return segP->startFreeSpace;
}



/************************************************************************/
/* SIGetFirstDataEntry(segP)  returns first data entry					*/
/************************************************************************/
static SISegEntry *
SIGetFirstDataEntry(SISeg *segP)
{
	SISegEntry *eP;
	Offset		startChain;

	startChain = SIGetStartEntryChain(segP);