SQLite

#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

typedef struct LogSummaryHdr LogSummaryHdr;
typedef struct LogSummary LogSummary;
typedef struct LogIterator LogIterator;
typedef struct LogLock LogLock;


/*
** The following structure may be used to store the same data that
** is stored in the log-summary header.
**

** This structure is used to implement an iterator that iterates through
** all frames in the log in database page order. Where two or more frames
** correspond to the same database page, the iterator visits only the 
** frame most recently written to the log.
**
** The internals of this structure are only accessed by:
**
**   logIteratorInit() - Create a new iterator,
**   logIteratorNext() - Step an iterator,
**   logIteratorFree() - Free an iterator.
**
** This functionality is used by the checkpoint code (see logCheckpoint()).
*/
struct LogIterator {
  int nSegment;                   /* Size of LogIterator.aSegment[] array */
  int nFinal;                     /* Elements in segment nSegment-1 */
  struct LogSegment {
    int iNext;                    /* Next aIndex index */
    u8 *aIndex;                   /* Pointer to index array */
    u32 *aDbPage;                 /* Pointer to db page array */
  } aSegment[1];
};

  u32 *aCksum,                    /* IN/OUT: Checksum values */
  u32 *piPage,                    /* OUT: Database page number for frame */
  u32 *pnTruncate,                /* OUT: New db size (or 0 if not commit) */
  int nData,                      /* Database page size (size of aData[]) */
  u8 *aData,                      /* Pointer to page data (for checksum) */
  u8 *aFrame                      /* Frame data */
){
  assert( LOG_FRAME_HDRSIZE==20 );

  logChecksumBytes(aFrame, 12, aCksum);
  logChecksumBytes(aData, nData, aCksum);

  if( aCksum[0]!=sqlite3Get4byte(&aFrame[12]) 
   || aCksum[1]!=sqlite3Get4byte(&aFrame[16]) 
  ){
    /* Checksum failed. */

      return SQLITE_NOMEM;
    }
    aData = &aFrame[LOG_FRAME_HDRSIZE];

    /* Read all frames from the log file. */
    iFrame = 0;
    iOffset = 0;
    for(iOffset=0; (iOffset+nFrame)<=nSize; iOffset+=nFrame){
      u32 pgno;                   /* Database page number for frame */
      u32 nTruncate;              /* dbsize field from frame header */
      int isValid;                /* True if this frame is valid */

      /* Read and decode the next log frame. */
      rc = sqlite3OsRead(pFd, aFrame, nFrame, iOffset);
      if( rc!=SQLITE_OK ) break;

    assert( !pSummary || pSummary->nRef==0 );
    sqlite3_free(pSummary);
  }
  *ppLog = pRet;
  return rc;
}

static int logIteratorNext(
  LogIterator *p,               /* Iterator */
  u32 *piPage,                    /* OUT: Next db page to write */
  u32 *piFrame                    /* OUT: Log frame to read from */
){
  u32 iMin = *piPage;
  u32 iRet = 0xFFFFFFFF;
  int i;
  int nBlock = p->nFinal;

    nBlock = 256;
  }

  *piPage = iRet;
  return (iRet==0xFFFFFFFF);
}

static LogIterator *logIteratorInit(Log *pLog){
  u32 *aData = pLog->pSummary->aData;
  LogIterator *p;                 /* Return value */
  int nSegment;                   /* Number of segments to merge */
  u32 iLast;                      /* Last frame in log */
  int nByte;                      /* Number of bytes to allocate */
  int i;                          /* Iterator variable */
  int nFinal;                     /* Number of unindexed entries */
  struct LogSegment *pFinal;      /* Final (unindexed) segment */
  u8 *aTmp;                       /* Temp space used by merge-sort */

  iLast = pLog->hdr.iLastPg;
  nSegment = (iLast >> 8) + 1;
  nFinal = (iLast & 0x000000FF);

  nByte = sizeof(LogIterator) + (nSegment-1)*sizeof(struct LogSegment) + 512;
  p = (LogIterator *)sqlite3_malloc(nByte);
  if( p ){
    memset(p, 0, nByte);
    p->nSegment = nSegment;
    p->nFinal = nFinal;
  }

  for(i=0; i<nSegment-1; i++){

  logMergesort8(pFinal->aDbPage, aTmp, pFinal->aIndex, &nFinal);
  p->nFinal = nFinal;

  return p;
}

/* 
** Free a log iterator allocated by logIteratorInit().
*/
static void logIteratorFree(LogIterator *p){
  sqlite3_free(p);
}

/*
** Checkpoint the contents of the log file.
*/
static int logCheckpoint(
  Log *pLog,                      /* Log connection */
  sqlite3_file *pFd,              /* File descriptor open on db file */
  u8 *zBuf                        /* Temporary buffer to use */
){
  int rc;                         /* Return code */
  int pgsz = pLog->hdr.pgsz;      /* Database page-size */
  LogIterator *pIter = 0;         /* Log iterator context */
  u32 iDbpage = 0;                /* Next database page to write */
  u32 iFrame = 0;                 /* Log frame containing data for iDbpage */

  if( pLog->hdr.iLastPg==0 ){
    return SQLITE_OK;
  }

  /* Allocate the iterator */
  pIter = logIteratorInit(pLog);
  if( !pIter ) return SQLITE_NOMEM;

  /* Sync the log file to disk */
  rc = sqlite3OsSync(pLog->pFd, pLog->sync_flags);
  if( rc!=SQLITE_OK ) goto out;

  /* Iterate through the contents of the log, copying data to the db file. */
  while( 0==logIteratorNext(pIter, &iDbpage, &iFrame) ){
    rc = sqlite3OsRead(pLog->pFd, zBuf, pgsz, 
        (iFrame-1) * (pgsz+LOG_FRAME_HDRSIZE) + LOG_FRAME_HDRSIZE
    );
    if( rc!=SQLITE_OK ) goto out;
    rc = sqlite3OsWrite(pFd, zBuf, pgsz, (iDbpage-1)*pgsz);
    if( rc!=SQLITE_OK ) goto out;
  }

  memset(zBuf, 0, LOG_FRAME_HDRSIZE);
  rc = sqlite3OsWrite(pLog->pFd, zBuf, LOG_FRAME_HDRSIZE, 0);
  if( rc!=SQLITE_OK ) goto out;
  rc = sqlite3OsSync(pLog->pFd, pLog->sync_flags);
#endif

 out:
  logIteratorFree(pIter);
  return rc;
}

/*
** Close a connection to a log file.
*/
int sqlite3LogClose(

static int pagerStress(void *p, PgHdr *pPg){
  Pager *pPager = (Pager *)p;
  int rc = SQLITE_OK;

  assert( pPg->pPager==pPager );
  assert( pPg->flags&PGHDR_DIRTY );

  pPg->pDirty = 0;
  if( pagerUseLog(pPager) ){
    /* Write a single frame for this page to the log. */

    rc = sqlite3LogFrames(pPager->pLog, pPager->pageSize, pPg, 0, 0, 0);
  }else{
    /* The doNotSync flag is set by the sqlite3PagerWrite() function while it
    ** is journalling a set of two or more database pages that are stored
    ** on the same disk sector. Syncing the journal is not allowed while
    ** this is happening as it is important that all members of such a
    ** set of pages are synced to disk together. So, if the page this function

        rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg)
    ) ){
      rc = subjournalPage(pPg);
    }
  
    /* Write the contents of the page out to the database file. */
    if( rc==SQLITE_OK ){

      rc = pager_write_pagelist(pPg);
    }
  }

  /* Mark the page as clean. */
  if( rc==SQLITE_OK ){
    PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));

    PRAGMA integrity_check;
  }
} {17 ok}
do_test wal-11.14 {
  list [expr [file size test.db]/1024] [expr [file size test.db-wal]/1044]
} {37 38}


#-------------------------------------------------------------------------
# This block of tests, wal-12.*, tests a problem...
#
reopen_db
do_test wal-12.1 {
  execsql {
    PRAGMA page_size = 1024;
    CREATE TABLE t1(x, y);
    CREATE TABLE t2(x, y);
    INSERT INTO t1 VALUES('A', 1);
  }
  list [expr [file size test.db]/1024] [expr [file size test.db-wal]/1044]
} {0 5}
do_test wal-12.2 {
  db close
  sqlite3_wal db test.db
  execsql {
    UPDATE t1 SET y = 0 WHERE x = 'A';
  }
  list [expr [file size test.db]/1024] [expr [file size test.db-wal]/1044]
} {3 1}
do_test wal-12.3 {
  execsql { INSERT INTO t2 VALUES('B', 1) }
  list [expr [file size test.db]/1024] [expr [file size test.db-wal]/1044]
} {3 2}

do_test wal-12.4 {
  file copy -force test.db test2.db
  file copy -force test.db-wal test2.db-wal
  sqlite3_wal db2 test2.db
breakpoint
  execsql { SELECT * FROM t2 } db2
} {B 1}
db2 close

file copy -force test.db-wal A
do_test wal-12.5 {
  execsql {
    PRAGMA checkpoint;
    UPDATE t2 SET y = 2 WHERE x = 'B'; 
    PRAGMA checkpoint;
    UPDATE t1 SET y = 1 WHERE x = 'A';
    PRAGMA checkpoint;
    UPDATE t1 SET y = 0 WHERE x = 'A';
    SELECT * FROM t2;
  }
} {B 2}
file copy -force test.db-wal B

do_test wal-12.4 {
  file copy -force test.db test2.db
  file copy -force test.db-wal test2.db-wal
  sqlite3_wal db2 test2.db
  execsql { SELECT * FROM t2 } db2
} {B 2}
db2 close


finish_test