SELECT indirect(1);
  DELETE FROM t2 WHERE x = 4;
  SELECT indirect(0);
  INSERT INTO t2 VALUES(4, 'new');
} {
  {UPDATE t2 0 X. {i 4 t y} {{} {} t new}}
}


















sqlite3session S db main
do_execsql_test 6.2.1 {
  SELECT indirect(0);
  SELECT indirect(-1);
  SELECT indirect(45);
  SELECT indirect(-100);

  SELECT indirect(1);
  DELETE FROM t2 WHERE x = 4;
  SELECT indirect(0);
  INSERT INTO t2 VALUES(4, 'new');
} {
  {UPDATE t2 0 X. {i 4 t y} {{} {} t new}}
}

do_iterator_test 6.1.8 * {
  CREATE TABLE t3(a, b PRIMARY KEY);
  CREATE TABLE t4(a, b PRIMARY KEY);
  CREATE TRIGGER t4t AFTER UPDATE ON t4 BEGIN
    UPDATE t3 SET a = new.a WHERE b = new.b;
  END;

  SELECT indirect(1);
  INSERT INTO t3 VALUES('one', 1);
  INSERT INTO t4 VALUES('one', 1);
  SELECT indirect(0);
  UPDATE t4 SET a = 'two' WHERE b = 1;
} {
  {INSERT t4 0 .X {} {t two i 1}} 
  {INSERT t3 1 .X {} {t two i 1}}
}

sqlite3session S db main
do_execsql_test 6.2.1 {
  SELECT indirect(0);
  SELECT indirect(-1);
  SELECT indirect(45);
  SELECT indirect(-100);

if {![info exists testdir]} {
  set testdir [file join [file dirname [info script]] .. .. test]
} 
source [file join [file dirname [info script]] session_common.tcl]
source $testdir/tester.tcl

set testprefix sessionfault



forcedelete test.db2
sqlite3 db2 test.db2
do_common_sql {
  CREATE TABLE t1(a, b, c, PRIMARY KEY(a, b));
  INSERT INTO t1 VALUES(1, 2, 3);
  INSERT INTO t1 VALUES(4, 5, 6);
................................................................................
  sqlite3session_foreach v $::changeset { lappend ::res $v }
  normalize_list $::res
} -test {
  faultsim_test_result [list 0 $::expected] {1 SQLITE_NOMEM}
}

faultsim_delete_and_reopen
do_test 9.prep {
  execsql { 
    PRAGMA encoding = 'utf16';
    CREATE TABLE t1(a PRIMARY KEY, b);
  }
} {}
faultsim_save_and_close


do_faultsim_test 9 -faults oom-transient -prep {
  catch { unset ::c }
  faultsim_restore_and_reopen
  sqlite3session S db main
  S attach *
} -body {
  execsql {
    INSERT INTO t1 VALUES('abcdefghijklmnopqrstuv', 'ABCDEFGHIJKLMNOPQRSTUV');
  }
  set ::c [S changeset]
  set {} {}
} -test {
  S delete
  faultsim_test_result {0 {}} {1 SQLITE_NOMEM} {1 {callback requested query abort}}
  if {[info exists ::c]} {

    set expected "{INSERT t1 0 X. {} {t abcdefghijklmnopqrstuv t ABCDEFGHIJKLMNOPQRSTUV}}"






































    if { [changeset_to_list $::c] != $expected } {
      error "changeset mismatch"
    }
  }
}



finish_test

if {![info exists testdir]} {
  set testdir [file join [file dirname [info script]] .. .. test]
} 
source [file join [file dirname [info script]] session_common.tcl]
source $testdir/tester.tcl

set testprefix sessionfault

if 1 {

forcedelete test.db2
sqlite3 db2 test.db2
do_common_sql {
  CREATE TABLE t1(a, b, c, PRIMARY KEY(a, b));
  INSERT INTO t1 VALUES(1, 2, 3);
  INSERT INTO t1 VALUES(4, 5, 6);
................................................................................
  sqlite3session_foreach v $::changeset { lappend ::res $v }
  normalize_list $::res
} -test {
  faultsim_test_result [list 0 $::expected] {1 SQLITE_NOMEM}
}

faultsim_delete_and_reopen
do_test 9.1.prep {
  execsql { 
    PRAGMA encoding = 'utf16';
    CREATE TABLE t1(a PRIMARY KEY, b);
  }
} {}
faultsim_save_and_close

set answers [list {0 {}} {1 SQLITE_NOMEM} {1 {callback requested query abort}}]
do_faultsim_test 9.1 -faults oom-transient -prep {
  catch { unset ::c }
  faultsim_restore_and_reopen
  sqlite3session S db main
  S attach *
} -body {
  execsql {
    INSERT INTO t1 VALUES('abcdefghijklmnopqrstuv', 'ABCDEFGHIJKLMNOPQRSTUV');
  }
  set ::c [S changeset]
  set {} {}
} -test {
  S delete
  eval faultsim_test_result $::answers
  if {[info exists ::c]} {
    set expected [normalize_list {
      {INSERT t1 0 X. {} {t abcdefghijklmnopqrstuv t ABCDEFGHIJKLMNOPQRSTUV}}
    }]
    if { [changeset_to_list $::c] != $expected } {
      error "changeset mismatch"
    }
  }
}

}

faultsim_delete_and_reopen
do_test 9.2.prep {
  execsql { 
    PRAGMA encoding = 'utf16';
    CREATE TABLE t1(a PRIMARY KEY, b);
    INSERT INTO t1 VALUES('abcdefghij', 'ABCDEFGHIJKLMNOPQRSTUV');
  }
} {}
faultsim_save_and_close

set answers [list {0 {}} {1 SQLITE_NOMEM} {1 {callback requested query abort}}]
do_faultsim_test 9.2 -faults oom-transient -prep {
  catch { unset ::c }
  faultsim_restore_and_reopen
  sqlite3session S db main
  S attach *
} -body {
  execsql {
    UPDATE t1 SET b = 'xyz';
  }
  set ::c [S changeset]
  set {} {}
} -test {
  S delete
  eval faultsim_test_result $::answers
  if {[info exists ::c]} {
    set expected [normalize_list {
      {UPDATE t1 0 X. {t abcdefghij t ABCDEFGHIJKLMNOPQRSTUV} {{} {} t xyz}}
    }]
    if { [changeset_to_list $::c] != $expected } {
      error "changeset mismatch"
    }
  }
}



finish_test

** SQLITE_NOMEM is returned.
*/
static int sessionSerializeValue(
  u8 *aBuf,                       /* If non-NULL, write serialized value here */
  sqlite3_value *pValue,          /* Value to serialize */
  int *pnWrite                    /* IN/OUT: Increment by bytes written */
){
  int eType;                      /* Value type (SQLITE_NULL, TEXT etc.) */
  int nByte;                      /* Size of serialized value in bytes */




  eType = sqlite3_value_type(pValue);
  if( aBuf ) aBuf[0] = eType;

  switch( eType ){
    case SQLITE_NULL: 
      nByte = 1;
      break;

    case SQLITE_INTEGER: 
    case SQLITE_FLOAT:
      if( aBuf ){
        /* TODO: SQLite does something special to deal with mixed-endian
        ** floating point values (e.g. ARM7). This code probably should
        ** too.  */
        u64 i;
        if( eType==SQLITE_INTEGER ){
          i = (u64)sqlite3_value_int64(pValue);
        }else{
          double r;
          assert( sizeof(double)==8 && sizeof(u64)==8 );
          r = sqlite3_value_double(pValue);
          memcpy(&i, &r, 8);
        }
        sessionPutI64(&aBuf[1], i);
      }
      nByte = 9; 
      break;

    default: {











      int n = sqlite3_value_bytes(pValue);
      int nVarint = sessionVarintLen(n);
      assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );

      if( aBuf ){
        sessionVarintPut(&aBuf[1], n);
        memcpy(&aBuf[nVarint + 1], eType==SQLITE_TEXT ? 
            sqlite3_value_text(pValue) : sqlite3_value_blob(pValue), n
        );
      }

      nByte = 1 + nVarint + n;
      break;
    }




  }

  *pnWrite += nByte;
  return SQLITE_OK;
}

#define HASH_APPEND(hash, add) ((hash) << 3) ^ (hash) ^ (unsigned int)(add)
................................................................................

  /* Grow the hash table if required */
  if( sessionGrowHash(pTab) ){
    pSession->rc = SQLITE_NOMEM;
    return;
  }

  /* Search the hash table for an existing entry for rowid=iKey2. If
  ** one is found, store a pointer to it in pChange and unlink it from
  ** the hash table. Otherwise, set pChange to NULL.
  */
  rc = sessionPreupdateHash(db, pTab, op==SQLITE_INSERT, &iHash, &bNullPk);


  if( rc==SQLITE_OK && bNullPk==0 ){

    SessionChange *pC;
    for(pC=pTab->apChange[iHash]; pC; pC=pC->pNext){
      int bEqual;
      sessionPreupdateEqual(db, pTab, pC, op==SQLITE_INSERT, &bEqual);
      if( bEqual ) break;
    }

    if( pC==0 ){
      /* Create a new change object containing all the old values (if
      ** this is an SQLITE_UPDATE or SQLITE_DELETE), or just the PK
      ** values (if this is an INSERT). */
      SessionChange *pChange; /* New change object */
      int nByte;              /* Number of bytes to allocate */
      int i;                  /* Used to iterate through columns */
  
      assert( rc==SQLITE_OK );
      pTab->nEntry++;
  
      /* Figure out how large an allocation is required */
      nByte = sizeof(SessionChange);
      for(i=0; i<pTab->nCol && rc==SQLITE_OK; i++){
        sqlite3_value *p = 0;
        if( op!=SQLITE_INSERT ){
          rc = sqlite3_preupdate_old(pSession->db, i, &p);

        }else if( 1 || pTab->abPK[i] ){
          rc = sqlite3_preupdate_new(pSession->db, i, &p);

        }
        if( p && rc==SQLITE_OK ){
          rc = sessionSerializeValue(0, p, &nByte);
        }




      }
  
      /* Allocate the change object */
      pChange = (SessionChange *)sqlite3_malloc(nByte);
      if( !pChange ){
        rc = SQLITE_NOMEM;

      }else{
        memset(pChange, 0, sizeof(SessionChange));
        pChange->aRecord = (u8 *)&pChange[1];
      }
  
      /* Populate the change object */



      nByte = 0;
      for(i=0; i<pTab->nCol && rc==SQLITE_OK; i++){
        sqlite3_value *p = 0;
        if( op!=SQLITE_INSERT ){
          rc = sqlite3_preupdate_old(pSession->db, i, &p);
        }else if( 1 || pTab->abPK[i] ){
          rc = sqlite3_preupdate_new(pSession->db, i, &p);
        }
        if( p && rc==SQLITE_OK ){
          rc = sessionSerializeValue(&pChange->aRecord[nByte], p, &nByte);
        }
      }
      if( rc==SQLITE_OK ){
        /* Add the change back to the hash-table */
        if( pSession->bIndirect || sqlite3_preupdate_depth(pSession->db) ){
          pChange->bIndirect = 1;
        }
        pChange->nRecord = nByte;
        pChange->bInsert = (op==SQLITE_INSERT);
        pChange->pNext = pTab->apChange[iHash];
        pTab->apChange[iHash] = pChange;
      }else{
        sqlite3_free(pChange);
      }
    }else if( rc==SQLITE_OK && pC->bIndirect ){
      /* If the existing change is considered "indirect", but this current
      ** change is "direct", mark the change object as direct. */
      if( sqlite3_preupdate_depth(pSession->db)==0 && pSession->bIndirect==0 ){
        pC->bIndirect = 0;
      }
    }
  }

  /* If an error has occurred, mark the session object as failed. */

  if( rc!=SQLITE_OK ){
    pSession->rc = rc;
  }
}

/*
** The 'pre-update' hook registered by this module with SQLite databases.
................................................................................
** Ensure that there is room in the buffer to append nByte bytes of data.
** If not, use sqlite3_realloc() to grow the buffer so that there is.
**
** If successful, return zero. Otherwise, if an OOM condition is encountered,
** set *pRc to SQLITE_NOMEM and return non-zero.
*/
static int sessionBufferGrow(SessionBuffer *p, int nByte, int *pRc){
  if( p->nAlloc-p->nBuf<nByte ){
    u8 *aNew;
    int nNew = p->nAlloc ? p->nAlloc : 128;
    do {
      nNew = nNew*2;
    }while( nNew<(p->nAlloc+nByte) );

    aNew = (u8 *)sqlite3_realloc(p->aBuf, nNew);
    if( 0==aNew ){
      *pRc = SQLITE_NOMEM;
      return 1;
    }
    p->aBuf = aNew;
    p->nAlloc = nNew;
  }

  return 0;
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a single byte to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendByte(SessionBuffer *p, u8 v, int *pRc){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, 1, pRc) ){
    p->aBuf[p->nBuf++] = v;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a single varint to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendVarint(SessionBuffer *p, int v, int *pRc){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, 9, pRc) ){
    p->nBuf += sessionVarintPut(&p->aBuf[p->nBuf], v);
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a blob of data to the buffer. 
................................................................................
*/
static void sessionAppendBlob(
  SessionBuffer *p, 
  const u8 *aBlob, 
  int nBlob, 
  int *pRc
){
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nBlob, pRc) ){
    memcpy(&p->aBuf[p->nBuf], aBlob, nBlob);
    p->nBuf += nBlob;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
................................................................................
*/
static void sessionAppendStr(
  SessionBuffer *p, 
  const char *zStr, 
  int *pRc
){
  int nStr = sqlite3Strlen30(zStr);
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nStr, pRc) ){
    memcpy(&p->aBuf[p->nBuf], zStr, nStr);
    p->nBuf += nStr;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
................................................................................
*/
static void sessionAppendIdent(
  SessionBuffer *p,               /* Buffer to a append to */
  const char *zStr,               /* String to quote, escape and append */
  int *pRc                        /* IN/OUT: Error code */
){
  int nStr = sqlite3Strlen30(zStr)*2 + 2 + 1;
  if( *pRc==SQLITE_OK && 0==sessionBufferGrow(p, nStr, pRc) ){
    char *zOut = (char *)&p->aBuf[p->nBuf];
    const char *zIn = zStr;
    *zOut++ = '"';
    while( *zIn ){
      if( *zIn=='"' ) *zOut++ = '"';
      *zOut++ = *(zIn++);
    }
................................................................................
        *pRc = SQLITE_NOMEM;
      }
    }
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is
** called. 
**
** Otherwse, if *pRc is SQLITE_OK, then it appends an update change to
** the buffer (see the comments under "CHANGESET FORMAT" at the top of the
** file). An update change consists of:
**
**   1 byte:  SQLITE_UPDATE (0x17)
**   n bytes: old.* record (see RECORD FORMAT)
**   m bytes: new.* record (see RECORD FORMAT)
**
** The SessionChange object passed as the third argument contains the
** values that were stored in the row when the session began (the old.*
................................................................................
** If all of the old.* values are equal to their corresponding new.* value
** (i.e. nothing has changed), then no data at all is appended to the buffer.
**
** Otherwise, the old.* record contains all primary key values and the 
** original values of any fields that have been modified. The new.* record 
** contains the new values of only those fields that have been modified.
*/ 
static void sessionAppendUpdate(
  SessionBuffer *pBuf,            /* Buffer to append to */
  sqlite3_stmt *pStmt,            /* Statement handle pointing at new row */
  SessionChange *p,               /* Object containing old values */
  u8 *abPK,                       /* Boolean array - true for PK columns */
  int *pRc                        /* IN/OUT: Error code */
){
  if( *pRc==SQLITE_OK ){
    SessionBuffer buf2 = {0,0,0}; /* Buffer to accumulate new.* record in */
    int bNoop = 1;                /* Set to zero if any values are modified */
    int nRewind = pBuf->nBuf;     /* Set to zero if any values are modified */
    int i;                        /* Used to iterate through columns */
    u8 *pCsr = p->aRecord;        /* Used to iterate through old.* values */

    sessionAppendByte(pBuf, SQLITE_UPDATE, pRc);
    sessionAppendByte(pBuf, p->bIndirect, pRc);
    for(i=0; i<sqlite3_column_count(pStmt); i++){
      int bChanged = 0;
      int nAdvance;
      int eType = *pCsr;
      switch( eType ){
        case SQLITE_NULL:
          nAdvance = 1;
          if( sqlite3_column_type(pStmt, i)!=SQLITE_NULL ){
            bChanged = 1;
          }
          break;

        case SQLITE_FLOAT:
        case SQLITE_INTEGER: {
          nAdvance = 9;
          if( eType==sqlite3_column_type(pStmt, i) ){
            sqlite3_int64 iVal = sessionGetI64(&pCsr[1]);
            if( eType==SQLITE_INTEGER ){
              if( iVal==sqlite3_column_int64(pStmt, i) ) break;
            }else{
              double dVal;
              memcpy(&dVal, &iVal, 8);
              if( dVal==sqlite3_column_double(pStmt, i) ) break;
            }
          }
          bChanged = 1;
          break;
        }

        default: {
          int nByte;
          int nHdr = 1 + sessionVarintGet(&pCsr[1], &nByte);
          assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
          nAdvance = nHdr + nByte;
          if( eType==sqlite3_column_type(pStmt, i) 
           && nByte==sqlite3_column_bytes(pStmt, i) 
           && 0==memcmp(&pCsr[nHdr], sqlite3_column_blob(pStmt, i), nByte)
          ){
            break;
          }
          bChanged = 1;
        }
      }

      if( bChanged || abPK[i] ){
        sessionAppendBlob(pBuf, pCsr, nAdvance, pRc);
      }else{
        sessionAppendByte(pBuf, 0, pRc);
      }

      if( bChanged ){
        sessionAppendCol(&buf2, pStmt, i, pRc);
        bNoop = 0;
      }else{
        sessionAppendByte(&buf2, 0, pRc);
      }

      pCsr += nAdvance;
    }

    if( bNoop ){
      pBuf->nBuf = nRewind;
    }else{
      sessionAppendBlob(pBuf, buf2.aBuf, buf2.nBuf, pRc);
    }
    sqlite3_free(buf2.aBuf);
  }

}

static int sessionSelectStmt(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Database name */
  const char *zTab,               /* Table name */
  int nCol,
................................................................................
  int rc = SQLITE_OK;
  u8 *a = pChange->aRecord;

  for(i=0; i<nCol && rc==SQLITE_OK; i++){
    int eType = *a++;

    switch( eType ){

      case SQLITE_NULL:
        assert( abPK[i]==0 );
        break;

      case SQLITE_INTEGER: {
        if( abPK[i] ){
          i64 iVal = sessionGetI64(a);
................................................................................

      nNoop = buf.nBuf;
      for(i=0; i<pTab->nChange && rc==SQLITE_OK; i++){
        SessionChange *p;         /* Used to iterate through changes */

        for(p=pTab->apChange[i]; rc==SQLITE_OK && p; p=p->pNext){
          rc = sessionSelectBind(pSel, nCol, abPK, p);

          if( sqlite3_step(pSel)==SQLITE_ROW ){
            int iCol;
            if( p->bInsert ){
              sessionAppendByte(&buf, SQLITE_INSERT, &rc);
              sessionAppendByte(&buf, p->bIndirect, &rc);
              for(iCol=0; iCol<nCol; iCol++){
                sessionAppendCol(&buf, pSel, iCol, &rc);
              }
            }else{
              sessionAppendUpdate(&buf, pSel, p, abPK, &rc);
            }
          }else if( !p->bInsert ){
            /* A DELETE change */
            sessionAppendByte(&buf, SQLITE_DELETE, &rc);
            sessionAppendByte(&buf, p->bIndirect, &rc);
            sessionAppendBlob(&buf, p->aRecord, p->nRecord, &rc);
          }

** SQLITE_NOMEM is returned.
*/
static int sessionSerializeValue(
  u8 *aBuf,                       /* If non-NULL, write serialized value here */
  sqlite3_value *pValue,          /* Value to serialize */
  int *pnWrite                    /* IN/OUT: Increment by bytes written */
){

  int nByte;                      /* Size of serialized value in bytes */

  if( pValue ){
    int eType;                    /* Value type (SQLITE_NULL, TEXT etc.) */
  
    eType = sqlite3_value_type(pValue);
    if( aBuf ) aBuf[0] = eType;
  
    switch( eType ){
      case SQLITE_NULL: 
        nByte = 1;
        break;
  
      case SQLITE_INTEGER: 
      case SQLITE_FLOAT:
        if( aBuf ){
          /* TODO: SQLite does something special to deal with mixed-endian
          ** floating point values (e.g. ARM7). This code probably should
          ** too.  */
          u64 i;
          if( eType==SQLITE_INTEGER ){
            i = (u64)sqlite3_value_int64(pValue);
          }else{
            double r;
            assert( sizeof(double)==8 && sizeof(u64)==8 );
            r = sqlite3_value_double(pValue);
            memcpy(&i, &r, 8);
          }
          sessionPutI64(&aBuf[1], i);
        }
        nByte = 9; 
        break;
  
      default: {
        u8 *z;
        int n;
        int nVarint;
  
        assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
        if( eType==SQLITE_TEXT ){
          z = (u8 *)sqlite3_value_text(pValue);
        }else{
          z = (u8 *)sqlite3_value_blob(pValue);
        }
        if( z==0 ) return SQLITE_NOMEM;
        n = sqlite3_value_bytes(pValue);
        nVarint = sessionVarintLen(n);

  
        if( aBuf ){
          sessionVarintPut(&aBuf[1], n);
          memcpy(&aBuf[nVarint + 1], eType==SQLITE_TEXT ? 
              sqlite3_value_text(pValue) : sqlite3_value_blob(pValue), n
          );
        }
  
        nByte = 1 + nVarint + n;
        break;
      }
    }
  }else{
    nByte = 1;
    if( aBuf ) aBuf[0] = '\0';
  }

  *pnWrite += nByte;
  return SQLITE_OK;
}

#define HASH_APPEND(hash, add) ((hash) << 3) ^ (hash) ^ (unsigned int)(add)
................................................................................

  /* Grow the hash table if required */
  if( sessionGrowHash(pTab) ){
    pSession->rc = SQLITE_NOMEM;
    return;
  }

  /* Calculate the hash-key for this change. If the primary key of the row
  ** includes a NULL value, exit early. Such changes are ignored by the
  ** session module. */

  rc = sessionPreupdateHash(db, pTab, op==SQLITE_INSERT, &iHash, &bNullPk);
  if( rc!=SQLITE_OK ) goto error_out;

  if( bNullPk==0 ){
    /* Search the hash table for an existing record for this row. */
    SessionChange *pC;
    for(pC=pTab->apChange[iHash]; pC; pC=pC->pNext){
      int bEqual;
      sessionPreupdateEqual(db, pTab, pC, op==SQLITE_INSERT, &bEqual);
      if( bEqual ) break;
    }

    if( pC==0 ){
      /* Create a new change object containing all the old values (if
      ** this is an SQLITE_UPDATE or SQLITE_DELETE), or just the PK
      ** values (if this is an INSERT). */
      SessionChange *pChange; /* New change object */
      int nByte;              /* Number of bytes to allocate */
      int i;                  /* Used to iterate through columns */
  
      assert( rc==SQLITE_OK );
      pTab->nEntry++;
  
      /* Figure out how large an allocation is required */
      nByte = sizeof(SessionChange);
      for(i=0; i<pTab->nCol; i++){
        sqlite3_value *p = 0;
        if( op!=SQLITE_INSERT ){
          TESTONLY(int trc = ) sqlite3_preupdate_old(pSession->db, i, &p);
          assert( trc==SQLITE_OK );
        }else if( pTab->abPK[i] ){
          TESTONLY(int trc = ) sqlite3_preupdate_new(pSession->db, i, &p);
          assert( trc==SQLITE_OK );
        }



        /* This may fail if SQLite value p contains a utf-16 string that must
        ** be converted to utf-8 and an OOM error occurs while doing so. */
        rc = sessionSerializeValue(0, p, &nByte);
        if( rc!=SQLITE_OK ) goto error_out;
      }
  
      /* Allocate the change object */
      pChange = (SessionChange *)sqlite3_malloc(nByte);
      if( !pChange ){
        rc = SQLITE_NOMEM;
        goto error_out;
      }else{
        memset(pChange, 0, sizeof(SessionChange));
        pChange->aRecord = (u8 *)&pChange[1];
      }
  
      /* Populate the change object. None of the preupdate_old(),
      ** preupdate_new() or SerializeValue() calls below may fail as all
      ** required values and encodings have already been cached in memory.
      ** It is not possible for an OOM to occur in this block. */
      nByte = 0;
      for(i=0; i<pTab->nCol; i++){
        sqlite3_value *p = 0;
        if( op!=SQLITE_INSERT ){
          sqlite3_preupdate_old(pSession->db, i, &p);
        }else if( pTab->abPK[i] ){
          sqlite3_preupdate_new(pSession->db, i, &p);
        }

        sessionSerializeValue(&pChange->aRecord[nByte], p, &nByte);
      }


      /* Add the change to the hash-table */
      if( pSession->bIndirect || sqlite3_preupdate_depth(pSession->db) ){
        pChange->bIndirect = 1;
      }
      pChange->nRecord = nByte;
      pChange->bInsert = (op==SQLITE_INSERT);
      pChange->pNext = pTab->apChange[iHash];
      pTab->apChange[iHash] = pChange;



    }else if( pC->bIndirect ){
      /* If the existing change is considered "indirect", but this current
      ** change is "direct", mark the change object as direct. */
      if( sqlite3_preupdate_depth(pSession->db)==0 && pSession->bIndirect==0 ){
        pC->bIndirect = 0;
      }
    }
  }

  /* If an error has occurred, mark the session object as failed. */
 error_out:
  if( rc!=SQLITE_OK ){
    pSession->rc = rc;
  }
}

/*
** The 'pre-update' hook registered by this module with SQLite databases.
................................................................................
** Ensure that there is room in the buffer to append nByte bytes of data.
** If not, use sqlite3_realloc() to grow the buffer so that there is.
**
** If successful, return zero. Otherwise, if an OOM condition is encountered,
** set *pRc to SQLITE_NOMEM and return non-zero.
*/
static int sessionBufferGrow(SessionBuffer *p, int nByte, int *pRc){
  if( *pRc==SQLITE_OK && p->nAlloc-p->nBuf<nByte ){
    u8 *aNew;
    int nNew = p->nAlloc ? p->nAlloc : 128;
    do {
      nNew = nNew*2;
    }while( nNew<(p->nAlloc+nByte) );

    aNew = (u8 *)sqlite3_realloc(p->aBuf, nNew);
    if( 0==aNew ){
      *pRc = SQLITE_NOMEM;
    }else{

      p->aBuf = aNew;
      p->nAlloc = nNew;
    }
  }
  return (*pRc!=SQLITE_OK);
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a single byte to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendByte(SessionBuffer *p, u8 v, int *pRc){
  if( 0==sessionBufferGrow(p, 1, pRc) ){
    p->aBuf[p->nBuf++] = v;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a single varint to the buffer. 
**
** If an OOM condition is encountered, set *pRc to SQLITE_NOMEM before
** returning.
*/
static void sessionAppendVarint(SessionBuffer *p, int v, int *pRc){
  if( 0==sessionBufferGrow(p, 9, pRc) ){
    p->nBuf += sessionVarintPut(&p->aBuf[p->nBuf], v);
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
** called. Otherwise, append a blob of data to the buffer. 
................................................................................
*/
static void sessionAppendBlob(
  SessionBuffer *p, 
  const u8 *aBlob, 
  int nBlob, 
  int *pRc
){
  if( 0==sessionBufferGrow(p, nBlob, pRc) ){
    memcpy(&p->aBuf[p->nBuf], aBlob, nBlob);
    p->nBuf += nBlob;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
................................................................................
*/
static void sessionAppendStr(
  SessionBuffer *p, 
  const char *zStr, 
  int *pRc
){
  int nStr = sqlite3Strlen30(zStr);
  if( 0==sessionBufferGrow(p, nStr, pRc) ){
    memcpy(&p->aBuf[p->nBuf], zStr, nStr);
    p->nBuf += nStr;
  }
}

/*
** This function is a no-op if *pRc is other than SQLITE_OK when it is 
................................................................................
*/
static void sessionAppendIdent(
  SessionBuffer *p,               /* Buffer to a append to */
  const char *zStr,               /* String to quote, escape and append */
  int *pRc                        /* IN/OUT: Error code */
){
  int nStr = sqlite3Strlen30(zStr)*2 + 2 + 1;
  if( 0==sessionBufferGrow(p, nStr, pRc) ){
    char *zOut = (char *)&p->aBuf[p->nBuf];
    const char *zIn = zStr;
    *zOut++ = '"';
    while( *zIn ){
      if( *zIn=='"' ) *zOut++ = '"';
      *zOut++ = *(zIn++);
    }
................................................................................
        *pRc = SQLITE_NOMEM;
      }
    }
  }
}

/*


**
** This function appends an update change to the buffer (see the comments 
** under "CHANGESET FORMAT" at the top of the file). An update change 
** consists of:
**
**   1 byte:  SQLITE_UPDATE (0x17)
**   n bytes: old.* record (see RECORD FORMAT)
**   m bytes: new.* record (see RECORD FORMAT)
**
** The SessionChange object passed as the third argument contains the
** values that were stored in the row when the session began (the old.*
................................................................................
** If all of the old.* values are equal to their corresponding new.* value
** (i.e. nothing has changed), then no data at all is appended to the buffer.
**
** Otherwise, the old.* record contains all primary key values and the 
** original values of any fields that have been modified. The new.* record 
** contains the new values of only those fields that have been modified.
*/ 
static int sessionAppendUpdate(
  SessionBuffer *pBuf,            /* Buffer to append to */
  sqlite3_stmt *pStmt,            /* Statement handle pointing at new row */
  SessionChange *p,               /* Object containing old values */
  u8 *abPK                        /* Boolean array - true for PK columns */

){
  int rc = SQLITE_OK;
  SessionBuffer buf2 = {0,0,0}; /* Buffer to accumulate new.* record in */
  int bNoop = 1;                /* Set to zero if any values are modified */
  int nRewind = pBuf->nBuf;     /* Set to zero if any values are modified */
  int i;                        /* Used to iterate through columns */
  u8 *pCsr = p->aRecord;        /* Used to iterate through old.* values */

  sessionAppendByte(pBuf, SQLITE_UPDATE, &rc);
  sessionAppendByte(pBuf, p->bIndirect, &rc);
  for(i=0; i<sqlite3_column_count(pStmt); i++){
    int bChanged = 0;
    int nAdvance;
    int eType = *pCsr;
    switch( eType ){
      case SQLITE_NULL:
        nAdvance = 1;
        if( sqlite3_column_type(pStmt, i)!=SQLITE_NULL ){
          bChanged = 1;
        }
        break;

      case SQLITE_FLOAT:
      case SQLITE_INTEGER: {
        nAdvance = 9;
        if( eType==sqlite3_column_type(pStmt, i) ){
          sqlite3_int64 iVal = sessionGetI64(&pCsr[1]);
          if( eType==SQLITE_INTEGER ){
            if( iVal==sqlite3_column_int64(pStmt, i) ) break;
          }else{
            double dVal;
            memcpy(&dVal, &iVal, 8);
            if( dVal==sqlite3_column_double(pStmt, i) ) break;
          }
        }
        bChanged = 1;
        break;
      }

      default: {
        int nByte;
        int nHdr = 1 + sessionVarintGet(&pCsr[1], &nByte);
        assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
        nAdvance = nHdr + nByte;
        if( eType==sqlite3_column_type(pStmt, i) 
         && nByte==sqlite3_column_bytes(pStmt, i) 
         && 0==memcmp(&pCsr[nHdr], sqlite3_column_blob(pStmt, i), nByte)
        ){
          break;
        }
        bChanged = 1;
      }
    }

    if( bChanged || abPK[i] ){
      sessionAppendBlob(pBuf, pCsr, nAdvance, &rc);
    }else{
      sessionAppendByte(pBuf, 0, &rc);
    }

    if( bChanged ){
      sessionAppendCol(&buf2, pStmt, i, &rc);
      bNoop = 0;
    }else{
      sessionAppendByte(&buf2, 0, &rc);
    }

    pCsr += nAdvance;
  }

  if( bNoop ){
    pBuf->nBuf = nRewind;
  }else{
    sessionAppendBlob(pBuf, buf2.aBuf, buf2.nBuf, &rc);
  }
  sqlite3_free(buf2.aBuf);

  return rc;
}

static int sessionSelectStmt(
  sqlite3 *db,                    /* Database handle */
  const char *zDb,                /* Database name */
  const char *zTab,               /* Table name */
  int nCol,
................................................................................
  int rc = SQLITE_OK;
  u8 *a = pChange->aRecord;

  for(i=0; i<nCol && rc==SQLITE_OK; i++){
    int eType = *a++;

    switch( eType ){
      case 0:
      case SQLITE_NULL:
        assert( abPK[i]==0 );
        break;

      case SQLITE_INTEGER: {
        if( abPK[i] ){
          i64 iVal = sessionGetI64(a);
................................................................................

      nNoop = buf.nBuf;
      for(i=0; i<pTab->nChange && rc==SQLITE_OK; i++){
        SessionChange *p;         /* Used to iterate through changes */

        for(p=pTab->apChange[i]; rc==SQLITE_OK && p; p=p->pNext){
          rc = sessionSelectBind(pSel, nCol, abPK, p);
          if( rc!=SQLITE_OK ) continue;
          if( sqlite3_step(pSel)==SQLITE_ROW ){
            int iCol;
            if( p->bInsert ){
              sessionAppendByte(&buf, SQLITE_INSERT, &rc);
              sessionAppendByte(&buf, p->bIndirect, &rc);
              for(iCol=0; iCol<nCol; iCol++){
                sessionAppendCol(&buf, pSel, iCol, &rc);
              }
            }else{
              rc = sessionAppendUpdate(&buf, pSel, p, abPK);
            }
          }else if( !p->bInsert ){
            /* A DELETE change */
            sessionAppendByte(&buf, SQLITE_DELETE, &rc);
            sessionAppendByte(&buf, p->bIndirect, &rc);
            sessionAppendBlob(&buf, p->aRecord, p->nRecord, &rc);
          }