SQLite

# include "sqliteInt.h"
# include "vdbeInt.h"
#endif

typedef struct SessionTable SessionTable;
typedef struct SessionChange SessionChange;
typedef struct SessionBuffer SessionBuffer;
typedef struct SessionInput SessionInput;

/*
** Minimum chunk size used by streaming versions of functions.
*/
#define SESSIONS_STR_CHUNK_SIZE 1024

/*
** Session handle structure.
*/
struct sqlite3_session {
  sqlite3 *db;                    /* Database handle session is attached to */
  char *zDb;                      /* Name of database session is attached to */
  int bEnable;                    /* True if currently recording */
  int bIndirect;                  /* True if all changes are indirect */
  int bAutoAttach;                /* True to auto-attach tables */
  int rc;                         /* Non-zero if an error has occurred */
  void *pFilterCtx;               /* First argument to pass to xTableFilter */
  int (*xTableFilter)(void *pCtx, const char *zTab);
  sqlite3_session *pNext;         /* Next session object on same db. */
  SessionTable *pTable;           /* List of attached tables */
};

/*
** Instances of this structure are used to build strings or binary records.
*/
struct SessionBuffer {
  u8 *aBuf;                       /* Pointer to changeset buffer */
  int nBuf;                       /* Size of buffer aBuf */
  int nAlloc;                     /* Size of allocation containing aBuf */
};

/*
** An object of this type is used internally as an abstraction for the 
** input data read by changeset iterators. Input data may be supplied 
** either as a single large buffer (sqlite3changeset_start()) or using
** a stream function (sqlite3changeset_start_str()).
*/
struct SessionInput {
  int iNext;                      /* Offset in aChangeset[] of next change */
  u8 *aChangeset;                 /* Pointer to buffer containing changeset */
  int nChangeset;                 /* Number of bytes in aChangeset */
  SessionBuffer buf;              /* Current read buffer */
  int (*xInput)(void*, void*, int*);        /* Input stream call (or NULL) */
  void *pIn;                                /* First argument to xInput */
  int bEof;                       /* Set to true after xInput finished */
};

/*
** Structure for changeset iterators.
*/
struct sqlite3_changeset_iter {
  SessionInput in;                /* Input buffer or stream */
  SessionBuffer tblhdr;           /* Buffer to hold apValue/zTab/abPK/ */
  int bPatchset;                  /* True if this is a patchset */

  int rc;                         /* Iterator error code */
  sqlite3_stmt *pConflict;        /* Points to conflicting row, if any */
  char *zTab;                     /* Current table */
  int nCol;                       /* Number of columns in zTab */
  int op;                         /* Current operation */
  int bIndirect;                  /* True if current change was indirect */
  u8 *abPK;                       /* Primary key array */

  int op;                         /* One of UPDATE, DELETE, INSERT */
  int bIndirect;                  /* True if this change is "indirect" */
  int nRecord;                    /* Number of bytes in buffer aRecord[] */
  u8 *aRecord;                    /* Buffer containing old.* record */
  SessionChange *pNext;           /* For hash-table collisions */
};










/*
** Write a varint with value iVal into the buffer at aBuf. Return the 
** number of bytes written.
*/
static int sessionVarintPut(u8 *aBuf, int iVal){
  return putVarint32(aBuf, iVal);
}

*/
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->nBuf+nByte) );

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

** stored in output variables *pnChangeset and *ppChangeset. Or, if an error
** occurs, an SQLite error code is returned and both output variables set 
** to 0.
*/
int sessionGenerateChangeset(
  sqlite3_session *pSession,      /* Session object */
  int bPatchset,                  /* True for patchset, false for changeset */
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut,                     /* First argument for xOutput */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
){
  sqlite3 *db = pSession->db;     /* Source database handle */
  SessionTable *pTab;             /* Used to iterate through attached tables */
  SessionBuffer buf = {0,0,0};    /* Buffer in which to accumlate changeset */
  int rc;                         /* Return code */

  assert( xOutput==0 || (pnChangeset==0 && ppChangeset==0 ) );

  /* Zero the output variables in case an error occurs. If this session
  ** object is already in the error state (sqlite3_session.rc != SQLITE_OK),
  ** this call will be a no-op.  */
  if( xOutput==0 ){
    *pnChangeset = 0;
    *ppChangeset = 0;
  }

  if( pSession->rc ) return pSession->rc;
  rc = sqlite3_exec(pSession->db, "SAVEPOINT changeset", 0, 0, 0);
  if( rc!=SQLITE_OK ) return rc;

  sqlite3_mutex_enter(sqlite3_db_mutex(db));

            }
          }else if( p->op!=SQLITE_INSERT ){
            rc = sessionAppendDelete(&buf, bPatchset, p, nCol, abPK);
          }
          if( rc==SQLITE_OK ){
            rc = sqlite3_reset(pSel);
          }

          /* If the buffer is now larger than SESSIONS_STR_CHUNK_SIZE, pass
          ** its contents to the xOutput() callback. */
          if( xOutput 
           && rc==SQLITE_OK 
           && buf.nBuf>nNoop 
           && buf.nBuf>SESSIONS_STR_CHUNK_SIZE 
          ){
            rc = xOutput(pOut, (void*)buf.aBuf, buf.nBuf);
            nNoop = -1;
            buf.nBuf = 0;
          }

        }
      }

      sqlite3_finalize(pSel);
      if( buf.nBuf==nNoop ){
        buf.nBuf = nRewind;
      }
      sqlite3_free((char*)azCol);  /* cast works around VC++ bug */
    }
  }

  if( rc==SQLITE_OK ){
    if( xOutput==0 ){
      *pnChangeset = buf.nBuf;
      *ppChangeset = buf.aBuf;
      buf.aBuf = 0;
    }else if( buf.nBuf>0 ){
      rc = xOutput(pOut, (void*)buf.aBuf, buf.nBuf);
    }
  }

  sqlite3_free(buf.aBuf);
  sqlite3_exec(db, "RELEASE changeset", 0, 0, 0);
  sqlite3_mutex_leave(sqlite3_db_mutex(db));
  return rc;
}

/*
** Obtain a changeset object containing all changes recorded by the 
** session object passed as the first argument.
**
** It is the responsibility of the caller to eventually free the buffer 
** using sqlite3_free().
*/
int sqlite3session_changeset(
  sqlite3_session *pSession,      /* Session object */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
){
  return sessionGenerateChangeset(pSession, 0, 0, 0, pnChangeset, ppChangeset);
}

/*
** Streaming version of sqlite3session_changeset().
*/
int sqlite3session_changeset_str(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
){
  return sessionGenerateChangeset(pSession, 0, xOutput, pOut, 0, 0);
}

/*
** Streaming version of sqlite3session_patchset().
*/
int sqlite3session_patchset_str(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
){
  return sessionGenerateChangeset(pSession, 1, xOutput, pOut, 0, 0);
}

/*
** Obtain a patchset object containing all changes recorded by the 
** session object passed as the first argument.
**
** It is the responsibility of the caller to eventually free the buffer 
** using sqlite3_free().
*/
int sqlite3session_patchset(
  sqlite3_session *pSession,      /* Session object */
  int *pnPatchset,                /* OUT: Size of buffer at *ppChangeset */
  void **ppPatchset               /* OUT: Buffer containing changeset */
){
  return sessionGenerateChangeset(pSession, 1, 0, 0, pnPatchset, ppPatchset);
}

/*
** Enable or disable the session object passed as the first argument.
*/
int sqlite3session_enable(sqlite3_session *pSession, int bEnable){
  int ret;

  }
  sqlite3_mutex_leave(sqlite3_db_mutex(pSession->db));

  return (ret==0);
}

/*
** Do the work for either sqlite3changeset_start() or start_str().
*/
int sessionChangesetStart(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn,
  int nChangeset,                 /* Size of buffer pChangeset in bytes */
  void *pChangeset                /* Pointer to buffer containing changeset */
){
  sqlite3_changeset_iter *pRet;   /* Iterator to return */
  int nByte;                      /* Number of bytes to allocate for iterator */

  assert( xInput==0 || (pChangeset==0 && nChangeset==0) );

  /* Zero the output variable in case an error occurs. */
  *pp = 0;

  /* Allocate and initialize the iterator structure. */
  nByte = sizeof(sqlite3_changeset_iter);
  pRet = (sqlite3_changeset_iter *)sqlite3_malloc(nByte);
  if( !pRet ) return SQLITE_NOMEM;
  memset(pRet, 0, sizeof(sqlite3_changeset_iter));
  pRet->in.aChangeset = (u8 *)pChangeset;
  pRet->in.nChangeset = nChangeset;
  pRet->in.xInput = xInput;
  pRet->in.pIn = pIn;
  pRet->in.iNext = 0;
  pRet->in.bEof = (xInput ? 0 : 1);

  /* Populate the output variable and return success. */
  *pp = pRet;
  return SQLITE_OK;
}

/*
** Create an iterator used to iterate through the contents of a changeset.
*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int nChangeset,                 /* Size of buffer pChangeset in bytes */
  void *pChangeset                /* Pointer to buffer containing changeset */
){
  return sessionChangesetStart(pp, 0, 0, nChangeset, pChangeset);
}

/*
** Streaming version of sqlite3changeset_start().
*/
int sqlite3changeset_start_str(
  sqlite3_changeset_iter **pp,    /* OUT: Changeset iterator handle */
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn
){
  return sessionChangesetStart(pp, xInput, pIn, 0, 0);
}

/*
** Ensure that there are at least nByte bytes available in the buffer. Or,
** if there are not nByte bytes remaining in the input, that all available
** data is in the buffer.
**
** Return an SQLite error code if an error occurs, or SQLITE_OK otherwise.
*/
static int sessionInputBuffer(SessionInput *pInput, int nByte){
  int rc = SQLITE_OK;
  if( pInput->xInput && !pInput->bEof ){
    assert( 0 );
  }
  return rc;
}

/*
** When this function is called, *ppRec points to the start of a record
** that contains nCol values. This function advances the pointer *ppRec
** until it points to the byte immediately following that record.
*/
static void sessionSkipRecord(
  u8 **ppRec,                     /* IN/OUT: Record pointer */
  int nCol                        /* Number of values in record */
){
  u8 *aRec = *ppRec;
  int i;
  for(i=0; i<nCol; i++){
    int eType = *aRec++;
    if( eType==SQLITE_TEXT || eType==SQLITE_BLOB ){
      int nByte;
      aRec += sessionVarintGet((u8*)aRec, &nByte);
      aRec += nByte;
    }else if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
      aRec += 8;
    }
  }

  *ppRec = aRec;
}

/*
** Deserialize a single record from a buffer in memory. See "RECORD FORMAT"
** for details.
**
** When this function is called, *paChange points to the start of the record
** to deserialize. Assuming no error occurs, *paChange is set to point to

** It is the responsibility of the caller to free all sqlite_value structures
** using sqlite3_free().
**
** If an error occurs, an SQLite error code (e.g. SQLITE_NOMEM) is returned.
** The apOut[] array may have been partially populated in this case.
*/
static int sessionReadRecord(
  SessionInput *pIn,              /* Input data */
  int nCol,                       /* Number of values in record */
  u8 *abPK,                       /* Array of primary key flags, or NULL */
  sqlite3_value **apOut           /* Write values to this array */
){
  int i;                          /* Used to iterate through columns */
  int rc = SQLITE_OK;

  for(i=0; i<nCol && rc==SQLITE_OK; i++){
    int eType = 0;                /* Type of value (SQLITE_NULL, TEXT etc.) */
    if( abPK && abPK[i]==0 ) continue;
    rc = sessionInputBuffer(pIn, 9);
    if( rc==SQLITE_OK ){
      eType = pIn->aChangeset[pIn->iNext++];
    }

    assert( !apOut || apOut[i]==0 );
    if( eType ){
      if( apOut ){
        apOut[i] = sqlite3ValueNew(0);
        if( !apOut[i] ) rc = SQLITE_NOMEM;
      }
    }

    if( rc==SQLITE_OK ){
      u8 *aVal = &pIn->aChangeset[pIn->iNext];
      if( eType==SQLITE_TEXT || eType==SQLITE_BLOB ){
        int nByte;
        pIn->iNext += sessionVarintGet(aVal, &nByte);
        rc = sessionInputBuffer(pIn, nByte);
        if( apOut && rc==SQLITE_OK ){
          u8 *aRec = &pIn->aChangeset[pIn->iNext];
          u8 enc = (eType==SQLITE_TEXT ? SQLITE_UTF8 : 0);
          sqlite3ValueSetStr(apOut[i], nByte, (char *)aRec, enc, SQLITE_STATIC);
        }
        pIn->iNext += nByte;
      }
      if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
        if( apOut ){
          sqlite3_int64 v = sessionGetI64(aVal);
          if( eType==SQLITE_INTEGER ){
            sqlite3VdbeMemSetInt64(apOut[i], v);
          }else{
            double d;
            memcpy(&d, &v, 8);
            sqlite3VdbeMemSetDouble(apOut[i], d);
          }
        }
        pIn->iNext += 8;
      }
    }
  }

  return rc;
}

/*
** The input pointer currently points to the second byte of a table-header.
** Specifically, to the following:
**
**   + number of columns in table (varint)
**   + array of PK flags (1 byte per column),
**   + table name (nul terminated).
**
** This function ensures that all of the above is present in the input 
** buffer (i.e. that it can be accessed without any calls to xInput()).
** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
** The input pointer is not moved.
*/
static int sessionChangesetBufferTblhdr(SessionInput *pIn, int *pnByte){
  int rc = SQLITE_OK;
  int nCol = 0;
  int iIn = pIn->iNext;

  rc = sessionInputBuffer(pIn, 9);
  if( rc==SQLITE_OK ){
    iIn += sessionVarintGet(&pIn->aChangeset[iIn], &nCol);
    rc = sessionInputBuffer(pIn, nCol+100);
    iIn += nCol;
  }
  while( rc==SQLITE_OK ){
    while( iIn<pIn->nChangeset && pIn->aChangeset[iIn] ) iIn++;
    if( pIn->aChangeset[iIn]==0 ) break;
    rc = sessionInputBuffer(pIn, 100);
  }
  if( pnByte ) *pnByte = (iIn+1 - pIn->iNext);
  return rc;
}

/*
** The input pointer currently points to the second byte of a table-header.
** Specifically, to the following:
**
**   + number of columns in table (varint)
**   + array of PK flags (1 byte per column),
**   + table name (nul terminated).
*/
static int sessionChangesetReadTblhdr(sqlite3_changeset_iter *p){
  int rc;
  int nCopy;
  assert( p->rc==SQLITE_OK );

  rc = sessionChangesetBufferTblhdr(&p->in, &nCopy);
  if( rc==SQLITE_OK ){
    int nByte;
    int nVarint;
    nVarint = sessionVarintGet(&p->in.aChangeset[p->in.iNext], &p->nCol);
    nCopy -= nVarint;
    p->in.iNext += nVarint;
    nByte = p->nCol * sizeof(sqlite3_value*) * 2 + nCopy;
    p->tblhdr.nBuf = 0;
    sessionBufferGrow(&p->tblhdr, nByte, &rc);
  }

  if( rc==SQLITE_OK ){
    int iPK = sizeof(sqlite3_value*)*p->nCol*2;
    memset(p->tblhdr.aBuf, 0, iPK);
    memcpy(&p->tblhdr.aBuf[iPK], &p->in.aChangeset[p->in.iNext], nCopy);
    p->in.iNext += nCopy;
  }

  p->apValue = (sqlite3_value**)p->tblhdr.aBuf;
  p->abPK = (u8*)&p->apValue[p->nCol*2];
  p->zTab = (char*)&p->abPK[p->nCol];
  return (p->rc = rc);
}

/*
** Advance the changeset iterator to the next change.
**
** If both paRec and pnRec are NULL, then this function works like the public
** API sqlite3changeset_next(). If SQLITE_ROW is returned, then the

** changes in the changeset.
*/
static int sessionChangesetNext(
  sqlite3_changeset_iter *p,      /* Changeset iterator */
  u8 **paRec,                     /* If non-NULL, store record pointer here */
  int *pnRec                      /* If non-NULL, store size of record here */
){

  int i;
  u8 op;

  assert( paRec==0 || p->in.xInput==0 ); /* fixme! */
  assert( (paRec==0 && pnRec==0) || (paRec && pnRec) );

  /* If the iterator is in the error-state, return immediately. */
  if( p->rc!=SQLITE_OK ) return p->rc;

  /* Free the current contents of p->apValue[], if any. */
  if( p->apValue ){
    for(i=0; i<p->nCol*2; i++){
      sqlite3ValueFree(p->apValue[i]);
    }
    memset(p->apValue, 0, sizeof(sqlite3_value*)*p->nCol*2);
  }

  /* Make sure the buffer contains at least 10 bytes of input data, or all
  ** remaining data if there are less than 10 bytes available. This is
  ** sufficient either for the 'T' or 'P' byte and the varint that follows
  ** it, or for the two single byte values otherwise. */
  p->rc = sessionInputBuffer(&p->in, 2);
  if( p->rc!=SQLITE_OK ) return p->rc;

  /* If the iterator is already at the end of the changeset, return DONE. */
  if( p->in.iNext>=p->in.nChangeset ){
    return SQLITE_DONE;
  }


  op = p->in.aChangeset[p->in.iNext++];
  if( op=='T' || op=='P' ){

    p->bPatchset = (op=='P');
    if( sessionChangesetReadTblhdr(p) ) return p->rc;
    if( (p->rc = sessionInputBuffer(&p->in, 2)) ) return p->rc;




    op = p->in.aChangeset[p->in.iNext++];






  }




  p->op = op;
  p->bIndirect = p->in.aChangeset[p->in.iNext++];
  if( p->op!=SQLITE_UPDATE && p->op!=SQLITE_DELETE && p->op!=SQLITE_INSERT ){
    return (p->rc = SQLITE_CORRUPT);
  }

  if( paRec ){ *paRec = &p->in.aChangeset[p->in.iNext]; }

  /* If this is an UPDATE or DELETE, read the old.* record. */
  if( p->op!=SQLITE_INSERT && (p->bPatchset==0 || p->op==SQLITE_DELETE) ){
    u8 *abPK = p->bPatchset ? p->abPK : 0;
    p->rc = sessionReadRecord(&p->in, p->nCol, abPK, paRec?0:p->apValue);
    if( p->rc!=SQLITE_OK ) return p->rc;
  }

  /* If this is an INSERT or UPDATE, read the new.* record. */
  if( p->op!=SQLITE_DELETE ){
    sqlite3_value **apOut = (paRec ? 0 : &p->apValue[p->nCol]);
    p->rc = sessionReadRecord(&p->in, p->nCol, 0, apOut);
    if( p->rc!=SQLITE_OK ) return p->rc;
  }

  if( pnRec ){
    *pnRec = (int)(&p->in.aChangeset[p->in.iNext] - *paRec);
  }else if( p->bPatchset && p->op==SQLITE_UPDATE ){
    /* If this is an UPDATE that is part of a patchset, then all PK and
    ** modified fields are present in the new.* record. The old.* record
    ** is currently completely empty. This block shifts the PK fields from
    ** new.* to old.*, to accommodate the code that reads these arrays.  */
    int i;
    for(i=0; i<p->nCol; i++){
      assert( p->apValue[i]==0 );
      assert( p->abPK[i]==0 || p->apValue[i+p->nCol] );
      if( p->abPK[i] ){
        p->apValue[i] = p->apValue[i+p->nCol];
        p->apValue[i+p->nCol] = 0;
      }
    }
  }

  return SQLITE_ROW;
}

/*
** Advance an iterator created by sqlite3changeset_start() to the next
** change in the changeset. This function may return SQLITE_ROW, SQLITE_DONE
** or SQLITE_CORRUPT.

*/
int sqlite3changeset_finalize(sqlite3_changeset_iter *p){
  int i;                          /* Used to iterate through p->apValue[] */
  int rc = p->rc;                 /* Return code */
  if( p->apValue ){
    for(i=0; i<p->nCol*2; i++) sqlite3ValueFree(p->apValue[i]);
  }
  sqlite3_free(p->tblhdr.aBuf);
  sqlite3_free(p);
  return rc;
}

/*
** Invert a changeset object.
*/
int sqlite3changeset_invert(
  int nChangeset,                 /* Number of bytes in input */
  const void *pChangeset,         /* Input changeset */
  int *pnInverted,                /* OUT: Number of bytes in output changeset */
  void **ppInverted               /* OUT: Inverse of pChangeset */
){
  int rc = SQLITE_OK;             /* Return value */
  u8 *aOut;
  u8 *aIn;
  int i;
  SessionInput sInput;
  int nCol = 0;                   /* Number of cols in current table */
  u8 *abPK = 0;                   /* PK array for current table */
  sqlite3_value **apVal = 0;      /* Space for values for UPDATE inversion */
  SessionBuffer sPK = {0, 0, 0};  /* PK array for current table */

  /* Zero the output variables in case an error occurs. */
  *ppInverted = 0;
  *pnInverted = 0;
  if( nChangeset==0 ) return SQLITE_OK;

  /* Set up the input stream */
  memset(&sInput, 0, sizeof(SessionInput));
  sInput.nChangeset = nChangeset;
  sInput.aChangeset = (u8*)pChangeset;

  aOut = (u8 *)sqlite3_malloc(nChangeset);
  if( !aOut ) return SQLITE_NOMEM;
  aIn = (u8 *)pChangeset;

  i = 0;
  while( i<nChangeset ){
    u8 eType;
    if( (rc = sessionInputBuffer(&sInput, 2)) ) goto finished_invert;
    eType = sInput.aChangeset[sInput.iNext];
    switch( eType ){
      case 'T': {
        /* A 'table' record consists of:
        **
        **   * A constant 'T' character,
        **   * Number of columns in said table (a varint),
        **   * An array of nCol bytes (sPK),
        **   * A nul-terminated table name.
        */
        int nByte;
        int nVarint;
        int iNext = sInput.iNext;
        sInput.iNext++;
        if( (rc = sessionChangesetBufferTblhdr(&sInput, &nByte)) ){
          goto finished_invert;
        }
        nVarint = sessionVarintGet(&sInput.aChangeset[iNext+1], &nCol);
        sPK.nBuf = 0;
        sessionAppendBlob(&sPK, &sInput.aChangeset[iNext+1+nVarint], nCol, &rc);
        if( rc ) goto finished_invert;
        sInput.iNext += nByte;

        memcpy(&aOut[i], &sInput.aChangeset[iNext], nByte+1);
        i += nByte+1;
        sqlite3_free(apVal);
        apVal = 0;
        abPK = sPK.aBuf;
        break;
      }

      case SQLITE_INSERT:
      case SQLITE_DELETE: {
        int iStart;
        int nByte;
        sInput.iNext += 2;
        iStart = sInput.iNext;
        sessionReadRecord(&sInput, nCol, 0, 0);
        aOut[i] = (eType==SQLITE_DELETE ? SQLITE_INSERT : SQLITE_DELETE);
        aOut[i+1] = aIn[i+1];               /* indirect-flag */
        nByte = sInput.iNext - iStart;
        memcpy(&aOut[i+2], &sInput.aChangeset[iStart], nByte);
        i += 2 + nByte;
        break;
      }

      case SQLITE_UPDATE: {
        int iCol;
        int nWrite = 0;


        if( 0==apVal ){
          apVal = (sqlite3_value **)sqlite3_malloc(sizeof(apVal[0])*nCol*2);
          if( 0==apVal ){
            rc = SQLITE_NOMEM;
            goto finished_invert;
          }
          memset(apVal, 0, sizeof(apVal[0])*nCol*2);
        }

        /* Write the header for the new UPDATE change. Same as the original. */
        aOut[i] = SQLITE_UPDATE;
        aOut[i+1] = sInput.aChangeset[sInput.iNext+1];
        nWrite = 2;

        /* Read the old.* and new.* records for the update change. */
        sInput.iNext += 2;
        rc = sessionReadRecord(&sInput, nCol, 0, &apVal[0]);
        if( rc==SQLITE_OK ){
          rc = sessionReadRecord(&sInput, nCol, 0, &apVal[nCol]);
        }






        /* Write the new old.* record. Consists of the PK columns from the
        ** original old.* record, and the other values from the original
        ** new.* record. */
        for(iCol=0; rc==SQLITE_OK && iCol<nCol; iCol++){
          sqlite3_value *pVal = apVal[iCol + (abPK[iCol] ? 0 : nCol)];
          rc = sessionSerializeValue(&aOut[i+nWrite], pVal, &nWrite);

        }
        memset(apVal, 0, sizeof(apVal[0])*nCol*2);
        if( rc!=SQLITE_OK ){
          goto finished_invert;
        }

        i += nWrite;
        assert( i==sInput.iNext );
        break;
      }

      default:
        rc = SQLITE_CORRUPT;
        goto finished_invert;
    }
  }

  assert( rc==SQLITE_OK );
  *pnInverted = nChangeset;
  *ppInverted = (void *)aOut;

 finished_invert:
  if( rc!=SQLITE_OK ){
    sqlite3_free(aOut);
  }
  sqlite3_free(apVal);
  sqlite3_free(sPK.aBuf);
  return rc;
}

typedef struct SessionApplyCtx SessionApplyCtx;
struct SessionApplyCtx {
  sqlite3 *db;
  sqlite3_stmt *pDelete;          /* DELETE statement */

      pNew->bIndirect = (bIndirect && pExist->bIndirect);
      aCsr = pNew->aRecord = (u8 *)&pNew[1];

      if( op1==SQLITE_INSERT ){             /* INSERT + UPDATE */
        u8 *a1 = aRec;
        assert( op2==SQLITE_UPDATE );
        pNew->op = SQLITE_INSERT;
        if( bPatchset==0 ) sessionSkipRecord(&a1, pTab->nCol);
        sessionMergeRecord(&aCsr, pTab->nCol, aExist, a1);
      }else if( op1==SQLITE_DELETE ){       /* DELETE + INSERT */
        assert( op2==SQLITE_INSERT );
        pNew->op = SQLITE_UPDATE;
        if( 0==sessionMergeUpdate(&aCsr, pTab, bPatchset, aExist, 0, aRec, 0) ){
          sqlite3_free(pNew);
          pNew = 0;
        }
      }else if( op2==SQLITE_UPDATE ){       /* UPDATE + UPDATE */
        u8 *a1 = aExist;
        u8 *a2 = aRec;
        assert( op1==SQLITE_UPDATE );
        if( bPatchset==0 ){
          sessionSkipRecord(&a1, pTab->nCol);
          sessionSkipRecord(&a2, pTab->nCol);
        }
        pNew->op = SQLITE_UPDATE;
        if( 0==sessionMergeUpdate(&aCsr, pTab, bPatchset, aRec, aExist,a1,a2) ){
          sqlite3_free(pNew);
          pNew = 0;
        }
      }else{                                /* UPDATE + DELETE */

    assert( bPatchset==0 || bPatchset==1 );
    assert( pIter->bPatchset==0 || pIter->bPatchset==1 );
    if( pIter->bPatchset!=bPatchset ){
      rc = SQLITE_ERROR;
      break;
    }


    sqlite3changeset_op(pIter, &zNew, &nCol, &op, &bIndirect);
    if( !pTab || sqlite3_stricmp(zNew, pTab->zName) ){





      /* Search the list for a matching table */
      int nNew = (int)strlen(zNew);
      u8 *abPK;

      sqlite3changeset_pk(pIter, &abPK, 0);
      for(pTab = *ppTabList; pTab; pTab=pTab->pNext){
        if( 0==sqlite3_strnicmp(pTab->zName, zNew, nNew+1) ) break;
      }
      if( !pTab ){
        pTab = sqlite3_malloc(sizeof(SessionTable) + nCol + nNew+1);
        if( !pTab ){
          rc = SQLITE_NOMEM;
          break;
        }
        memset(pTab, 0, sizeof(SessionTable));
        pTab->pNext = *ppTabList;
        pTab->nCol = nCol;
        pTab->abPK = (u8*)&pTab[1];
        memcpy(pTab->abPK, abPK, nCol);
        pTab->zName = (char*)&pTab->abPK[nCol];
        memcpy(pTab->zName, zNew, nNew+1);
        *ppTabList = pTab;
      }else if( pTab->nCol!=nCol || memcmp(pTab->abPK, abPK, nCol) ){
        rc = SQLITE_SCHEMA;
        break;
      }

    }

    if( sessionGrowHash(bPatchset, pTab) ){
      rc = SQLITE_NOMEM;
      break;
    }
    iHash = sessionChangeHash(

** resulting changeset will contain an UPDATE change that updates both fields.
*/
int sqlite3session_changeset(
  sqlite3_session *pSession,      /* Session object */
  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
  void **ppChangeset              /* OUT: Buffer containing changeset */
);


/*
** This function is similar to sqlite3session_changeset(), except that instead
** of storing the output changeset in a buffer obtained from sqlite3_malloc()
** it invokes the supplied xOutput() callback zero or more times to stream the
** changeset to the application. This is useful in order to avoid large memory
** allocations when working with very large changesets.
**
** The first parameter passed to each call to the xOutput callback is a copy
** of the pOut parameter passed to this function. The following two parameters
** are a pointer to the buffer containing the next chunk of the output changeset
** and the size of that buffer in bytes.
**
** If the data is successfully processed by the xOutput callback, it should
** return SQLITE_OK. Or, if an error occurs, some other SQLite error code. In
** this case the sqlite3session_changeset_str() call is abandoned immediately
** and returns a copy of the xOutput return code.
*/
int sqlite3session_changeset_str(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);


/*
** CAPI3REF: Generate A Patchset From A Session Object
**
** The differences between a patchset and a changeset are that:
**
** <ul>

** in the same way as for changesets.
*/
int sqlite3session_patchset(
  sqlite3_session *pSession,      /* Session object */
  int *pnPatchset,                /* OUT: Size of buffer at *ppChangeset */
  void **ppPatchset               /* OUT: Buffer containing changeset */
);

/*
** Streaming version of sqlite3session_patchset().
*/
int sqlite3session_patchset_str(
  sqlite3_session *pSession,
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut
);

/*
** CAPI3REF: Test if a changeset has recorded any changes.
**
** Return non-zero if no changes to attached tables have been recorded by 
** the session object passed as the first argument. Otherwise, if one or 
** more changes have been recorded, return zero.

*/
int sqlite3changeset_start(
  sqlite3_changeset_iter **pp,    /* OUT: New changeset iterator handle */
  int nChangeset,                 /* Size of changeset blob in bytes */
  void *pChangeset                /* Pointer to blob containing changeset */
);


/*
** This function is similar to sqlite3changeset_start(), except that instead
** of reading data from a single buffer, it requests it one chunk at a time
** from the application by invoking the supplied xInput() callback. The xInput()
** callback may be invoked at any time during the lifetime of the iterator.
**
** Each time the xInput callback is invoked, the first argument passed is a
** copy of the third parameter passed to this function. The second argument,
** pData, points to a buffer (*pnData) bytes in size. Assuming no error occurs
** the xInput method should copy up to (*pnData) bytes of data into the buffer
** and set (*pnData) to the actual number of bytes copied before returning
** SQLITE_OK. If the input is completely exhausted, (*pnData) should be set
** to zero to indicate this. Or, if an error occurs, an SQLite error code
** should be returned. In this case the iterator is put into an error state and
** all subsequent calls to iterator methods return a copy of the xInput error
** code.
*/
int sqlite3changeset_start_str(
  sqlite3_changeset_iter **pp,
  int (*xInput)(void *pIn, void *pData, int *pnData),
  void *pIn
);

/*
** CAPI3REF: Advance A Changeset Iterator
**
** This function may only be used with iterators created by function
** [sqlite3changeset_start()]. If it is called on an iterator passed to
** a conflict-handler callback by [sqlite3changeset_apply()], SQLITE_MISUSE
** is returned and the call has no effect.

typedef struct TestSession TestSession;
struct TestSession {
  sqlite3_session *pSession;
  Tcl_Interp *interp;
  Tcl_Obj *pFilterScript;
};

#define SESSION_STREAM_TCL_VAR "sqlite3session_streams"

/*
** Attempt to find the global variable zVar within interpreter interp
** and extract a boolean value from it. Return this value.
**
** If the named variable cannot be found, or if it cannot be interpreted
** as a boolean, return 0.
*/
static int test_tcl_boolean(Tcl_Interp *interp, const char *zVar){
  Tcl_Obj *pObj;
  int bVal = 0;
  pObj = Tcl_ObjGetVar2(interp, Tcl_NewStringObj(zVar, -1), 0, TCL_GLOBAL_ONLY);
  if( pObj ) Tcl_GetBooleanFromObj(0, pObj, &bVal);
  return bVal;
}

static int test_session_error(Tcl_Interp *interp, int rc){
  extern const char *sqlite3ErrName(int);
  Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
  return TCL_ERROR;
}

    /* printf("error: %s\n", Tcl_GetStringResult(p->interp)); */
    Tcl_BackgroundError(p->interp);
  }
  Tcl_DecrRefCount(pEval);

  return bRes;
}

struct TestSessionsBlob {
  void *p;
  int n;
};
typedef struct TestSessionsBlob TestSessionsBlob;

static int testSessionsOutput(
  void *pCtx,
  const void *pData,
  int nData
){
  TestSessionsBlob *pBlob = (TestSessionsBlob*)pCtx;
  char *pNew;

  assert( nData>0 );
  pNew = (char*)sqlite3_realloc(pBlob->p, pBlob->n + nData);
  if( pNew==0 ){
    return SQLITE_NOMEM;
  }
  pBlob->p = (void*)pNew;
  memcpy(&pNew[pBlob->n], pData, nData);
  pBlob->n += nData;
  return SQLITE_OK;
}

/*
** Tclcmd:  $session attach TABLE
**          $session changeset
**          $session delete
**          $session enable BOOL
**          $session indirect INTEGER
**          $session patchset
**          $session table_filter SCRIPT
*/
static int test_session_cmd(
  void *clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]

        return test_session_error(interp, rc);
      }
      break;
    }

    case 7:        /* patchset */
    case 1: {      /* changeset */
      TestSessionsBlob o = {0, 0};
      if( test_tcl_boolean(interp, SESSION_STREAM_TCL_VAR) ){
        void *pCtx = (void*)&o;
        if( iSub==7 ){
          rc = sqlite3session_patchset_str(pSession, testSessionsOutput, pCtx);
        }else{
          rc = sqlite3session_changeset_str(pSession, testSessionsOutput, pCtx);
        }
      }else{
        if( iSub==7 ){
          rc = sqlite3session_patchset(pSession, &o.n, &o.p);
        }else{
          rc = sqlite3session_changeset(pSession, &o.n, &o.p);
        }
      }
      if( rc==SQLITE_OK ){
        Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(o.p, o.n)); 
      }
      sqlite3_free(o.p);

      if( rc!=SQLITE_OK ){
        return test_session_error(interp, rc);
      }
      break;
    }

    case 2:        /* delete */
      Tcl_DeleteCommand(interp, Tcl_GetString(objv[0]));

test_suite "session_eec" -description {
  All session module related tests with sqlite3_extended_result_codes() set. 
} -files [
  glob -nocomplain $::testdir/../ext/session/*.test
] -dbconfig {
  sqlite3_extended_result_codes $::dbhandle 1
}

test_suite "session_str" -description {
  All session module related tests using the streaming APIs.
} -files [
  glob -nocomplain $::testdir/../ext/session/*.test
] -dbconfig {
  set ::sqlite3session_streams 1
}

test_suite "no_optimization" -description {
  Run test scripts with optimizations disabled using the
  sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS) interface.
} -files {
  where.test where2.test where3.test where4.test where5.test
  where6.test where7.test where8.test where9.test