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Overview
Comment:Make selecting the asynchronous IO file-locking mode a runtime operation. Still untested. (CVS 6544)
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SHA1:577277e84a05707b8c21aa08bc5fc314c1ac38ac
User & Date: danielk1977 2009-04-24 10:13:06
Context
2009-04-24
14:51
Make sure that the optimizer realizes that an "x IS NULL" contraint does not necessarily give a single-row result even on a UNIQUE index. Ticket #3824. (CVS 6545) check-in: 207335fd user: drh tags: trunk
10:13
Make selecting the asynchronous IO file-locking mode a runtime operation. Still untested. (CVS 6544) check-in: 577277e8 user: danielk1977 tags: trunk
09:27
Improve comments and documentation of the asynchronous IO VFS module. (CVS 6543) check-in: 92bc6be2 user: danielk1977 tags: trunk
Changes
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Changes to ext/async/sqlite3async.c.

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**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** $Id: sqlite3async.c,v 1.2 2009/04/24 09:27:16 danielk1977 Exp $
**
** This file contains the implementation of an asynchronous IO backend 
** for SQLite.
*/

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO)

#include "sqlite3async.h"


#define ENABLE_FILE_LOCKING



/* Useful macros used in several places */
#define MIN(x,y) ((x)<(y)?(x):(y))
#define MAX(x,y) ((x)>(y)?(x):(y))

/* Forward references */
typedef struct AsyncWrite AsyncWrite;
typedef struct AsyncFile AsyncFile;
typedef struct AsyncFileData AsyncFileData;
typedef struct AsyncFileLock AsyncFileLock;
typedef struct AsyncLock AsyncLock;

/* Enable for debugging */


static int sqlite3async_trace = 0;
# define ASYNC_TRACE(X) if( sqlite3async_trace ) asyncTrace X
static void asyncTrace(const char *zFormat, ...){
  char *z;
  va_list ap;
  va_start(ap, zFormat);
  z = sqlite3_vmprintf(zFormat, ap);
  va_end(ap);
  fprintf(stderr, "[%d] %s", 0 /* (int)pthread_self() */, z);
  sqlite3_free(z);
}


/*
** THREAD SAFETY NOTES
**
** Basic rules:
**
**     * Both read and write access to the global write-op queue must be 
................................................................................
*/
static struct TestAsyncStaticData {
  AsyncWrite *pQueueFirst;     /* Next write operation to be processed */
  AsyncWrite *pQueueLast;      /* Last write operation on the list */
  AsyncLock *pLock;            /* Linked list of all AsyncLock structures */
  volatile int ioDelay;        /* Extra delay between write operations */
  volatile int eHalt;          /* One of the SQLITEASYNC_HALT_XXX values */

  int ioError;                 /* True if an IO error has occurred */
  int nFile;                   /* Number of open files (from sqlite pov) */
} async = { 0,0,0,0,0,0,0 };

/* Possible values of AsyncWrite.op */
#define ASYNC_NOOP          0
#define ASYNC_WRITE         1
#define ASYNC_SYNC          2
#define ASYNC_TRUNCATE      3
#define ASYNC_CLOSE         4
................................................................................
** structures is allocated) and stored in the async.aLock hash table. The
** keys for async.aLock are the full pathnames of the opened files.
**
** AsyncLock.pList points to the head of a linked list of AsyncFileLock
** structures, one for each handle currently open on the file.
**
** If the opened file is not a main-database (the SQLITE_OPEN_MAIN_DB is
** not passed to the sqlite3OsOpen() call), or if ENABLE_FILE_LOCKING is 
** not defined at compile time, variables AsyncLock.pFile and 
** AsyncLock.eLock are never used. Otherwise, pFile is a file handle
** opened on the file in question and used to obtain the file-system 
** locks required by database connections within this process.
**
** See comments above the asyncLock() function for more details on 
** the implementation of database locking used by this backend.
*/
struct AsyncLock {
  char *zFile;
  int nFile;
................................................................................
  if( zName && rc==SQLITE_OK ){
    pLock = findLock(pData->zName, pData->nName);
    if( !pLock ){
      int nByte = pVfs->szOsFile + sizeof(AsyncLock) + pData->nName + 1; 
      pLock = (AsyncLock *)sqlite3_malloc(nByte);
      if( pLock ){
        memset(pLock, 0, nByte);
#ifdef ENABLE_FILE_LOCKING
        if( flags&SQLITE_OPEN_MAIN_DB ){
          pLock->pFile = (sqlite3_file *)&pLock[1];
          rc = pVfs->xOpen(pVfs, pData->zName, pLock->pFile, flags, 0);
          if( rc!=SQLITE_OK ){
            sqlite3_free(pLock);
            pLock = 0;
          }
        }
#endif
        if( pLock ){
          pLock->nFile = pData->nName;
          pLock->zFile = &((char *)(&pLock[1]))[pVfs->szOsFile];
          memcpy(pLock->zFile, pData->zName, pLock->nFile);
          pLock->pNext = async.pLock;
          async.pLock = pLock;
        }
................................................................................
  switch( op ){
    case SQLITEASYNC_HALT: {
      int eWhen = va_arg(ap, int);
      if( eWhen!=SQLITEASYNC_HALT_NEVER
       && eWhen!=SQLITEASYNC_HALT_NOW
       && eWhen!=SQLITEASYNC_HALT_IDLE
      ){
        return SQLITE_ERROR;
      }
      async.eHalt = eWhen;
      async_mutex_enter(ASYNC_MUTEX_QUEUE);
      async_cond_signal(ASYNC_COND_QUEUE);
      async_mutex_leave(ASYNC_MUTEX_QUEUE);
      break;
    }

    case SQLITEASYNC_DELAY: {
      int iDelay = va_arg(ap, int);



      async.ioDelay = iDelay;
      break;
    }












      
    case SQLITEASYNC_GET_HALT: {
      int *peWhen = va_arg(ap, int *);
      *peWhen = async.eHalt;
      break;
    }
    case SQLITEASYNC_GET_DELAY: {
      int *piDelay = va_arg(ap, int *);
      *piDelay = async.ioDelay;
      break;





    }

    default:
      return SQLITE_ERROR;
  }
  return SQLITE_OK;
}

#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO) */








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**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** $Id: sqlite3async.c,v 1.3 2009/04/24 10:13:06 danielk1977 Exp $
**
** This file contains the implementation of an asynchronous IO backend 
** for SQLite.
*/

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO)

#include "sqlite3async.h"

#include "sqlite3.h"
#include <stdarg.h>
#include <string.h>
#include <assert.h>

/* Useful macros used in several places */
#define MIN(x,y) ((x)<(y)?(x):(y))
#define MAX(x,y) ((x)>(y)?(x):(y))

/* Forward references */
typedef struct AsyncWrite AsyncWrite;
typedef struct AsyncFile AsyncFile;
typedef struct AsyncFileData AsyncFileData;
typedef struct AsyncFileLock AsyncFileLock;
typedef struct AsyncLock AsyncLock;

/* Enable for debugging */
#ifndef NDEBUG
#include <stdio.h>
static int sqlite3async_trace = 0;
# define ASYNC_TRACE(X) if( sqlite3async_trace ) asyncTrace X
static void asyncTrace(const char *zFormat, ...){
  char *z;
  va_list ap;
  va_start(ap, zFormat);
  z = sqlite3_vmprintf(zFormat, ap);
  va_end(ap);
  fprintf(stderr, "[%d] %s", 0 /* (int)pthread_self() */, z);
  sqlite3_free(z);
}
#endif

/*
** THREAD SAFETY NOTES
**
** Basic rules:
**
**     * Both read and write access to the global write-op queue must be 
................................................................................
*/
static struct TestAsyncStaticData {
  AsyncWrite *pQueueFirst;     /* Next write operation to be processed */
  AsyncWrite *pQueueLast;      /* Last write operation on the list */
  AsyncLock *pLock;            /* Linked list of all AsyncLock structures */
  volatile int ioDelay;        /* Extra delay between write operations */
  volatile int eHalt;          /* One of the SQLITEASYNC_HALT_XXX values */
  volatile int bLockFiles;     /* Current value of "lockfiles" parameter */
  int ioError;                 /* True if an IO error has occurred */
  int nFile;                   /* Number of open files (from sqlite pov) */
} async = { 0,0,0,0,0,1,0,0 };

/* Possible values of AsyncWrite.op */
#define ASYNC_NOOP          0
#define ASYNC_WRITE         1
#define ASYNC_SYNC          2
#define ASYNC_TRUNCATE      3
#define ASYNC_CLOSE         4
................................................................................
** structures is allocated) and stored in the async.aLock hash table. The
** keys for async.aLock are the full pathnames of the opened files.
**
** AsyncLock.pList points to the head of a linked list of AsyncFileLock
** structures, one for each handle currently open on the file.
**
** If the opened file is not a main-database (the SQLITE_OPEN_MAIN_DB is
** not passed to the sqlite3OsOpen() call), or if async.bLockFiles is 
** false, variables AsyncLock.pFile and AsyncLock.eLock are never used. 
** Otherwise, pFile is a file handle opened on the file in question and 
** used to obtain the file-system locks required by database connections 
** within this process.
**
** See comments above the asyncLock() function for more details on 
** the implementation of database locking used by this backend.
*/
struct AsyncLock {
  char *zFile;
  int nFile;
................................................................................
  if( zName && rc==SQLITE_OK ){
    pLock = findLock(pData->zName, pData->nName);
    if( !pLock ){
      int nByte = pVfs->szOsFile + sizeof(AsyncLock) + pData->nName + 1; 
      pLock = (AsyncLock *)sqlite3_malloc(nByte);
      if( pLock ){
        memset(pLock, 0, nByte);

        if( async.bLockFiles && (flags&SQLITE_OPEN_MAIN_DB) ){
          pLock->pFile = (sqlite3_file *)&pLock[1];
          rc = pVfs->xOpen(pVfs, pData->zName, pLock->pFile, flags, 0);
          if( rc!=SQLITE_OK ){
            sqlite3_free(pLock);
            pLock = 0;
          }
        }

        if( pLock ){
          pLock->nFile = pData->nName;
          pLock->zFile = &((char *)(&pLock[1]))[pVfs->szOsFile];
          memcpy(pLock->zFile, pData->zName, pLock->nFile);
          pLock->pNext = async.pLock;
          async.pLock = pLock;
        }
................................................................................
  switch( op ){
    case SQLITEASYNC_HALT: {
      int eWhen = va_arg(ap, int);
      if( eWhen!=SQLITEASYNC_HALT_NEVER
       && eWhen!=SQLITEASYNC_HALT_NOW
       && eWhen!=SQLITEASYNC_HALT_IDLE
      ){
        return SQLITE_MISUSE;
      }
      async.eHalt = eWhen;
      async_mutex_enter(ASYNC_MUTEX_QUEUE);
      async_cond_signal(ASYNC_COND_QUEUE);
      async_mutex_leave(ASYNC_MUTEX_QUEUE);
      break;
    }

    case SQLITEASYNC_DELAY: {
      int iDelay = va_arg(ap, int);
      if( iDelay<0 ){
        return SQLITE_MISUSE;
      }
      async.ioDelay = iDelay;
      break;
    }

    case SQLITEASYNC_LOCKFILES: {
      int bLock = va_arg(ap, int);
      async_mutex_enter(ASYNC_MUTEX_QUEUE);
      if( async.nFile || async.pQueueFirst ){
        async_mutex_leave(ASYNC_MUTEX_QUEUE);
        return SQLITE_MISUSE;
      }
      async.bLockFiles = bLock;
      async_mutex_leave(ASYNC_MUTEX_QUEUE);
      break;
    }
      
    case SQLITEASYNC_GET_HALT: {
      int *peWhen = va_arg(ap, int *);
      *peWhen = async.eHalt;
      break;
    }
    case SQLITEASYNC_GET_DELAY: {
      int *piDelay = va_arg(ap, int *);
      *piDelay = async.ioDelay;
      break;
    }
    case SQLITEASYNC_GET_LOCKFILES: {
      int *piDelay = va_arg(ap, int *);
      *piDelay = async.bLockFiles;
      break;
    }

    default:
      return SQLITE_ERROR;
  }
  return SQLITE_OK;
}

#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ASYNCIO) */

Changes to src/test_async.c.

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**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** $Id: test_async.c,v 1.59 2009/04/23 14:58:40 danielk1977 Exp $
**
** This file contains a binding of the asynchronous IO extension interface
** (defined in ext/async/sqlite3async.h) to Tcl.
*/

#define TCL_THREADS 
#include <tcl.h>
................................................................................
  Tcl_ThreadId x;
  const int nStack = TCL_THREAD_STACK_DEFAULT;
  const int flags = TCL_THREAD_NOFLAGS;
  int rc;

  rc = Tcl_CreateThread(&x, tclWriterThread, threadData, nStack, flags);
  if( rc!=TCL_OK ){

    return TCL_ERROR;
  }
  while( isStarted==0 ){
#if 0
    sched_yield();
#endif
  }

  return TCL_OK;
}

/*
** sqlite3async_wait
**
** Wait for the current writer thread to terminate.







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**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** $Id: test_async.c,v 1.60 2009/04/24 10:13:06 danielk1977 Exp $
**
** This file contains a binding of the asynchronous IO extension interface
** (defined in ext/async/sqlite3async.h) to Tcl.
*/

#define TCL_THREADS 
#include <tcl.h>
................................................................................
  Tcl_ThreadId x;
  const int nStack = TCL_THREAD_STACK_DEFAULT;
  const int flags = TCL_THREAD_NOFLAGS;
  int rc;

  rc = Tcl_CreateThread(&x, tclWriterThread, threadData, nStack, flags);
  if( rc!=TCL_OK ){
    Tcl_AppendResult(interp, "Tcl_CreateThread() failed", 0);
    return TCL_ERROR;
  }





  while( isStarted==0 ) { /* Busy loop */ }
  return TCL_OK;
}

/*
** sqlite3async_wait
**
** Wait for the current writer thread to terminate.