SQLite

/*
** This function is called from both BtreeCommitPhaseTwo() and BtreeRollback()
** at the conclusion of a transaction.
*/
static void btreeEndTransaction(Btree *p){
  BtShared *pBt = p->pBt;
  sqlite3 *db = p->db;
  assert( sqlite3BtreeHoldsMutex(p) );

#ifndef SQLITE_OMIT_AUTOVACUUM
  pBt->bDoTruncate = 0;
#endif
  if( p->inTrans>TRANS_NONE && db->nVdbeActive>1 ){
    /* If there are other active statements that belong to this database
    ** handle, downgrade to a read-only transaction. The other statements
    ** may still be reading from the database.  */
    downgradeAllSharedCacheTableLocks(p);
    p->inTrans = TRANS_READ;
  }else{
    /* If the handle had any kind of transaction open, decrement the 

  int aLimit[SQLITE_N_LIMIT];   /* Limits */
  struct sqlite3InitInfo {      /* Information used during initialization */
    int newTnum;                /* Rootpage of table being initialized */
    u8 iDb;                     /* Which db file is being initialized */
    u8 busy;                    /* TRUE if currently initializing */
    u8 orphanTrigger;           /* Last statement is orphaned TEMP trigger */
  } init;
  int nVdbeActive;              /* Number of VDBEs currently running */
  int nVdbeRead;                /* Number of active VDBEs that read or write */
  int nVdbeWrite;               /* Number of active VDBEs that read and write */
  int nVdbeExec;                /* Number of nested calls to VdbeExec() */
  int nExtension;               /* Number of loaded extensions */
  void **aExtension;            /* Array of shared library handles */
  void (*xTrace)(void*,const char*);        /* Trace function */
  void *pTraceArg;                          /* Argument to the trace function */
  void (*xProfile)(void*,const char*,u64);  /* Profiling function */
  void *pProfileArg;                        /* Argument to profile function */
  void *pCommitArg;                 /* Argument to xCommitCallback() */   

  sqlite3VdbeEnter(p);
  if( p->rc==SQLITE_NOMEM ){
    /* This happens if a malloc() inside a call to sqlite3_column_text() or
    ** sqlite3_column_text16() failed.  */
    goto no_mem;
  }
  assert( p->rc==SQLITE_OK || p->rc==SQLITE_BUSY );
  assert( p->bIsReader || p->readOnly!=0 );
  p->rc = SQLITE_OK;
  assert( p->explain==0 );
  p->pResultSet = 0;
  db->busyHandler.nBusy = 0;
  CHECK_FOR_INTERRUPT;
  sqlite3VdbeIOTraceSql(p);
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK

** will automatically commit when the VDBE halts.
**
** If P2 is zero, then a read-lock is obtained on the database file.
*/
case OP_Transaction: {
  Btree *pBt;

  assert( p->bIsReader );
  assert( p->readOnly==0 || pOp->p2==0 );
  assert( pOp->p1>=0 && pOp->p1<db->nDb );
  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p1))!=0 );
  pBt = db->aDb[pOp->p1].pBt;

  if( pBt ){
    rc = sqlite3BtreeBeginTrans(pBt, pOp->p2);

** executing this instruction.
*/
case OP_ReadCookie: {               /* out2-prerelease */
  int iMeta;
  int iDb;
  int iCookie;

  assert( p->bIsReader );
  iDb = pOp->p1;
  iCookie = pOp->p3;
  assert( pOp->p3<SQLITE_N_BTREE_META );
  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pBt!=0 );
  assert( (p->btreeMask & (((yDbMask)1)<<iDb))!=0 );

  int iMeta;
  int iGen;
  Btree *pBt;

  assert( pOp->p1>=0 && pOp->p1<db->nDb );
  assert( (p->btreeMask & (((yDbMask)1)<<pOp->p1))!=0 );
  assert( sqlite3SchemaMutexHeld(db, pOp->p1, 0) );
  assert( p->bIsReader );
  pBt = db->aDb[pOp->p1].pBt;
  if( pBt ){
    sqlite3BtreeGetMeta(pBt, BTREE_SCHEMA_VERSION, (u32 *)&iMeta);
    iGen = db->aDb[pOp->p1].pSchema->iGeneration;
  }else{
    iGen = iMeta = 0;
  }

  int wrFlag;
  Btree *pX;
  VdbeCursor *pCur;
  Db *pDb;

  assert( (pOp->p5&(OPFLAG_P2ISREG|OPFLAG_BULKCSR))==pOp->p5 );
  assert( pOp->opcode==OP_OpenWrite || pOp->p5==0 );
  assert( p->bIsReader );
  assert( pOp->opcode==OP_OpenRead || p->readOnly==0 );

  if( p->expired ){
    rc = SQLITE_ABORT;
    break;
  }

  int nRoot;      /* Number of tables to check.  (Number of root pages.) */
  int *aRoot;     /* Array of rootpage numbers for tables to be checked */
  int j;          /* Loop counter */
  int nErr;       /* Number of errors reported */
  char *z;        /* Text of the error report */
  Mem *pnErr;     /* Register keeping track of errors remaining */

  assert( p->bIsReader );
  nRoot = pOp->p2;
  assert( nRoot>0 );
  aRoot = sqlite3DbMallocRaw(db, sizeof(int)*(nRoot+1) );
  if( aRoot==0 ) goto no_mem;
  assert( pOp->p3>0 && pOp->p3<=p->nMem );
  pnErr = &aMem[pOp->p3];
  assert( (pnErr->flags & MEM_Int)!=0 );

*/
case OP_VOpen: {
  VdbeCursor *pCur;
  sqlite3_vtab_cursor *pVtabCursor;
  sqlite3_vtab *pVtab;
  sqlite3_module *pModule;

  assert( p->bIsReader );
  pCur = 0;
  pVtabCursor = 0;
  pVtab = pOp->p4.pVtab->pVtab;
  pModule = (sqlite3_module *)pVtab->pModule;
  assert(pVtab && pModule);
  rc = pModule->xOpen(pVtab, &pVtabCursor);
  importVtabErrMsg(p, pVtab);

  bft explain:2;          /* True if EXPLAIN present on SQL command */
  bft inVtabMethod:2;     /* See comments above */
  bft changeCntOn:1;      /* True to update the change-counter */
  bft expired:1;          /* True if the VM needs to be recompiled */
  bft runOnlyOnce:1;      /* Automatically expire on reset */
  bft usesStmtJournal:1;  /* True if uses a statement journal */
  bft readOnly:1;         /* True for statements that do not write */
  bft bIsReader:1;        /* True for statements that read */
  bft isPrepareV2:1;      /* True if prepared with prepare_v2() */
  bft doingRerun:1;       /* True if rerunning after an auto-reprepare */
  int nChange;            /* Number of db changes made since last reset */
  yDbMask btreeMask;      /* Bitmask of db->aDb[] entries referenced */
  yDbMask lockMask;       /* Subset of btreeMask that requires a lock */
  int iStatement;         /* Statement number (or 0 if has not opened stmt) */
  int aCounter[4];        /* Counters used by sqlite3_stmt_status() */

    if( db->xProfile && !db->init.busy ){
      sqlite3OsCurrentTimeInt64(db->pVfs, &p->startTime);
    }
#endif

    db->nVdbeActive++;
    if( p->readOnly==0 ) db->nVdbeWrite++;
    if( p->bIsReader ) db->nVdbeRead++;
    p->pc = 0;
  }
#ifndef SQLITE_OMIT_EXPLAIN
  if( p->explain ){
    rc = sqlite3VdbeList(p);
  }else
#endif /* SQLITE_OMIT_EXPLAIN */

*/
static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs){
  int i;
  int nMaxArgs = *pMaxFuncArgs;
  Op *pOp;
  int *aLabel = p->aLabel;
  p->readOnly = 1;
  p->bIsReader = 0;
  for(pOp=p->aOp, i=p->nOp-1; i>=0; i--, pOp++){
    u8 opcode = pOp->opcode;

    pOp->opflags = sqlite3OpcodeProperty[opcode];
    if( opcode==OP_Function || opcode==OP_AggStep ){
      if( pOp->p5>nMaxArgs ) nMaxArgs = pOp->p5;
    }else if( opcode==OP_Transaction ){
      if( pOp->p2!=0 ) p->readOnly = 0;
      p->bIsReader = 1;
    }else if( opcode==OP_Vacuum
           || opcode==OP_JournalMode
#ifndef SQLITE_OMIT_VIRTUALTABLE
           || opcode==OP_Checkpoint
#endif
    ){
      p->readOnly = 0;
      p->bIsReader = 1;
#ifndef SQLITE_OMIT_VIRTUALTABLE
    }else if( opcode==OP_VUpdate ){
      if( pOp->p2>nMaxArgs ) nMaxArgs = pOp->p2;
    }else if( opcode==OP_VFilter ){
      int n;
      assert( p->nOp - i >= 3 );
      assert( pOp[-1].opcode==OP_Integer );

  int nWrite = 0;
  int nRead = 0;
  p = db->pVdbe;
  while( p ){
    if( p->magic==VDBE_MAGIC_RUN && p->pc>=0 ){
      cnt++;
      if( p->readOnly==0 ) nWrite++;
      if( p->bIsReader ) nRead++;
    }
    p = p->pNext;
  }
  assert( cnt==db->nVdbeActive );
  assert( nWrite==db->nVdbeWrite );
  assert( nRead==db->nVdbeRead );
}

    sqlite3VdbeLeave(p);
  }

  /* We have successfully halted and closed the VM.  Record this fact. */
  if( p->pc>=0 ){
    db->nVdbeActive--;
    if( !p->readOnly ) db->nVdbeWrite--;
    if( p->bIsReader ) db->nVdbeRead--;
    assert( db->nVdbeActive>=db->nVdbeRead );
    assert( db->nVdbeRead>=db->nVdbeWrite );
    assert( db->nVdbeWrite>=0 );
  }
  p->magic = VDBE_MAGIC_HALT;
  checkActiveVdbeCnt(db);
  if( p->db->mallocFailed ){