{DELETE t1 0 X. {i 3 t Thonburi} {}} 
  {INSERT t1 0 X. {} {i 20 t Thapae}} 
}

do_changeset_invert_test 2.3.3 S {
  {DELETE t1 0 X. {i 10 t Sukhothai} {}} 
  {INSERT t1 0 X. {} {i 1 t Sukhothai}} 
  {UPDATE t1 0 X. {{} {} t Surin} {i 2 t Ayutthaya}} 
  {INSERT t1 0 X. {} {i 3 t Thonburi}} 
  {DELETE t1 0 X. {i 20 t Thapae} {}}
}
do_test 2.3.4 { S delete } {}

do_test 2.4.1 {
  sqlite3session S db main
................................................................................
  sqlite3session S db main
  S attach t5
  execsql { DELETE FROM t5 }
  S isempty
} {1}
do_test 8.4 { S delete } {}














catch { db2 close }
finish_test

  {DELETE t1 0 X. {i 3 t Thonburi} {}} 
  {INSERT t1 0 X. {} {i 20 t Thapae}} 
}

do_changeset_invert_test 2.3.3 S {
  {DELETE t1 0 X. {i 10 t Sukhothai} {}} 
  {INSERT t1 0 X. {} {i 1 t Sukhothai}} 
  {UPDATE t1 0 X. {i 2 t Surin} {{} {} t Ayutthaya}} 
  {INSERT t1 0 X. {} {i 3 t Thonburi}} 
  {DELETE t1 0 X. {i 20 t Thapae} {}}
}
do_test 2.3.4 { S delete } {}

do_test 2.4.1 {
  sqlite3session S db main
................................................................................
  sqlite3session S db main
  S attach t5
  execsql { DELETE FROM t5 }
  S isempty
} {1}
do_test 8.4 { S delete } {}

#-------------------------------------------------------------------------
#
do_execsql_test 9.1 {
  CREATE TABLE t7(a, b, c, d, e PRIMARY KEY, f, g);
  INSERT INTO t7 VALUES(1, 1, 1, 1, 1, 1, 1);
}
do_test 9.2 { 
  sqlite3session S db main 
  S attach *
  execsql { UPDATE t7 SET b=2, d=2 }
} {}
do_changeset_test 9.2 S {{UPDATE t7 0 ....X.. {{} {} i 1 {} {} i 1 i 1 {} {} {} {}} {{} {} i 2 {} {} i 2 {} {} {} {} {} {}}}}
S delete
catch { db2 close }
finish_test

# 2011 July 13
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    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.
#
#***********************************************************************
# This file implements regression tests for SQLite library.
#

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
ifcapable !session {finish_test; return}

set testprefix session8

proc noop {args} {}

# Like [dbcksum] in tester.tcl. Except this version is not sensitive
# to changes in the value of implicit IPK columns.
#
proc udbcksum {db dbname} {
  if {$dbname=="temp"} {
    set master sqlite_temp_master
  } else {
    set master $dbname.sqlite_master
  }
  set alltab [$db eval "SELECT name FROM $master WHERE type='table'"]
  set txt [$db eval "SELECT * FROM $master"]\n
  foreach tab $alltab {
    append txt [lsort [$db eval "SELECT * FROM $dbname.$tab"]]\n
  }
  return [md5 $txt]
}

proc do_then_undo {tn sql} {
  set ck1 [udbcksum db main]

  sqlite3session S db main
  S attach *
  db eval $sql

  set ck2 [udbcksum db main]
  
  set invert [sqlite3changeset_invert [S changeset]]
  S delete
  sqlite3changeset_apply db $invert noop

  set ck3 [udbcksum db main]

  set a [expr {$ck1==$ck2}]
  set b [expr {$ck1==$ck3}]
  uplevel [list do_test $tn.1 "set {} $a" 0]
  uplevel [list do_test $tn.2 "set {} $b" 1]
}

do_execsql_test 1.1 {
  CREATE TABLE t1(a PRIMARY KEY, b);
  INSERT INTO t1 VALUES(1, 2);
  INSERT INTO t1 VALUES("abc", "xyz");
}
do_then_undo 1.2 { INSERT INTO t1 VALUES(3, 4); }
do_then_undo 1.3 { DELETE FROM t1 WHERE b=2; }
do_then_undo 1.4 { UPDATE t1 SET b = 3 WHERE a = 1; }

do_execsql_test 2.1 {
  CREATE TABLE t2(a, b PRIMARY KEY);
  INSERT INTO t2 VALUES(1, 2);
  INSERT INTO t2 VALUES('abc', 'xyz');
}
do_then_undo 1.2 { INSERT INTO t2 VALUES(3, 4); }
do_then_undo 1.3 { DELETE FROM t2 WHERE b=2; }
do_then_undo 1.4 { UPDATE t1 SET a = '123' WHERE b = 'xyz'; }

do_execsql_test 3.1 {
  CREATE TABLE t3(a, b, c, d, e, PRIMARY KEY(c, e));
  INSERT INTO t3 VALUES('x', 45, 0.0, 'abcdef', 12);
  INSERT INTO t3 VALUES(45, 0.0, 'abcdef', 12, 'x');
  INSERT INTO t3 VALUES(0.0, 'abcdef', 12, 'x', 45);
}

do_then_undo 3.2 { UPDATE t3 SET b=b||b WHERE e!='x' }
do_then_undo 3.3 { UPDATE t3 SET a = 46 }

finish_test

}

/*
** Invert a changeset object.
*/
int sqlite3changeset_invert(
  int nChangeset,                 /* Number of bytes in input */
  void *pChangeset,               /* Input changeset */
  int *pnInverted,                /* OUT: Number of bytes in output changeset */
  void **ppInverted               /* OUT: Inverse of pChangeset */
){

  u8 *aOut;
  u8 *aIn;
  int i;
  int nCol = 0;



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

  aOut = (u8 *)sqlite3_malloc(nChangeset);
................................................................................
        **
        **   * A constant 'T' character,
        **   * Number of columns in said table (a varint),
        **   * An array of nCol bytes (abPK),
        **   * A nul-terminated table name.
        */
        int nByte = 1 + sessionVarintGet(&aIn[i+1], &nCol);

        nByte += nCol;
        nByte += 1 + sqlite3Strlen30((char *)&aIn[i+nByte]);
        memcpy(&aOut[i], &aIn[i], nByte);
        i += nByte;


        break;
      }

      case SQLITE_INSERT:
      case SQLITE_DELETE: {
        int nByte;
        u8 *aEnd = &aIn[i+2];
................................................................................
        nByte = (int)(aEnd - &aIn[i+2]);
        memcpy(&aOut[i+2], &aIn[i+2], nByte);
        i += 2 + nByte;
        break;
      }

      case SQLITE_UPDATE: {
        int nByte1;              /* Size of old.* record in bytes */
        int nByte2;              /* Size of new.* record in bytes */
        u8 *aEnd = &aIn[i+2];    











        sessionReadRecord(&aEnd, nCol, 0);
        nByte1 = (int)(aEnd - &aIn[i+2]);

        sessionReadRecord(&aEnd, nCol, 0);
        nByte2 = (int)(aEnd - &aIn[i+2]) - nByte1;



        aOut[i] = SQLITE_UPDATE;
        aOut[i+1] = aIn[i+1];
        memcpy(&aOut[i+2], &aIn[i+2+nByte1], nByte2);
        memcpy(&aOut[i+2+nByte2], &aIn[i+2], nByte1);


        i += 2 + nByte1 + nByte2;


























        break;
      }

      default:
        sqlite3_free(aOut);
        return SQLITE_CORRUPT;
    }
  }


  *pnInverted = nChangeset;
  *ppInverted = (void *)aOut;






  return SQLITE_OK;
}

typedef struct SessionApplyCtx SessionApplyCtx;
struct SessionApplyCtx {
  sqlite3 *db;
  sqlite3_stmt *pDelete;          /* DELETE statement */
  sqlite3_stmt *pUpdate;          /* DELETE statement */
  sqlite3_stmt *pInsert;          /* INSERT statement */
  sqlite3_stmt *pSelect;          /* SELECT statement */
  int nCol;                       /* Size of azCol[] and abPK[] arrays */
  const char **azCol;             /* Array of column names */
  u8 *abPK;                       /* Boolean array - true if column is in PK */
};

................................................................................
        assert( op2==SQLITE_INSERT );
        pNew->op = SQLITE_UPDATE;
        if( 0==sessionMergeUpdate(&aCsr, pTab, pExist->aRecord, 0, aRec, 0) ){
          sqlite3_free(pNew);
          pNew = 0;
        }
      }else if( op2==SQLITE_UPDATE ){       /* UPDATE + UPDATE */
        assert( op1==SQLITE_UPDATE );
        u8 *a1 = pExist->aRecord;
        u8 *a2 = aRec;

        sessionReadRecord(&a1, pTab->nCol, 0);
        sessionReadRecord(&a2, pTab->nCol, 0);
        pNew->op = SQLITE_UPDATE;
        if( 0==sessionMergeUpdate(&aCsr, pTab, aRec, pExist->aRecord, a1, a2) ){
          sqlite3_free(pNew);
          pNew = 0;
        }

}

/*
** 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;
  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 */

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

  aOut = (u8 *)sqlite3_malloc(nChangeset);
................................................................................
        **
        **   * A constant 'T' character,
        **   * Number of columns in said table (a varint),
        **   * An array of nCol bytes (abPK),
        **   * A nul-terminated table name.
        */
        int nByte = 1 + sessionVarintGet(&aIn[i+1], &nCol);
        abPK = &aIn[i+nByte];
        nByte += nCol;
        nByte += 1 + sqlite3Strlen30((char *)&aIn[i+nByte]);
        memcpy(&aOut[i], &aIn[i], nByte);
        i += nByte;
        sqlite3_free(apVal);
        apVal = 0;
        break;
      }

      case SQLITE_INSERT:
      case SQLITE_DELETE: {
        int nByte;
        u8 *aEnd = &aIn[i+2];
................................................................................
        nByte = (int)(aEnd - &aIn[i+2]);
        memcpy(&aOut[i+2], &aIn[i+2], nByte);
        i += 2 + nByte;
        break;
      }

      case SQLITE_UPDATE: {
        int iCol;
        int nWrite = 0;
        u8 *aEnd = &aIn[i+2];

        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);
        }

        /* Read the old.* and new.* records for the update change. */
        rc = sessionReadRecord(&aEnd, nCol, &apVal[0]);

        if( rc==SQLITE_OK ){
          rc = sessionReadRecord(&aEnd, nCol, &apVal[nCol]);

        }

        /* Write the header for the new UPDATE change. Same as the original. */
        aOut[i] = SQLITE_UPDATE;
        aOut[i+1] = aIn[i+1];


        nWrite = 2;


        /* 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);
        }

        /* Write the new new.* record. Consists of a copy of all values
        ** from the original old.* record, except for the PK columns, which
        ** are set to "undefined". */
        for(iCol=0; rc==SQLITE_OK && iCol<nCol; iCol++){
          sqlite3_value *pVal = (abPK[iCol] ? 0 : apVal[iCol]);
          rc = sessionSerializeValue(&aOut[i+nWrite], pVal, &nWrite);
        }

        for(iCol=0; iCol<nCol*2; iCol++){
          sqlite3ValueFree(apVal[iCol]);
        }
        memset(apVal, 0, sizeof(apVal[0])*nCol*2);
        if( rc!=SQLITE_OK ){
          goto finished_invert;
        }

        i += nWrite;
        assert( &aIn[i]==aEnd );
        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);
  return rc;
}

typedef struct SessionApplyCtx SessionApplyCtx;
struct SessionApplyCtx {
  sqlite3 *db;
  sqlite3_stmt *pDelete;          /* DELETE statement */
  sqlite3_stmt *pUpdate;          /* UPDATE statement */
  sqlite3_stmt *pInsert;          /* INSERT statement */
  sqlite3_stmt *pSelect;          /* SELECT statement */
  int nCol;                       /* Size of azCol[] and abPK[] arrays */
  const char **azCol;             /* Array of column names */
  u8 *abPK;                       /* Boolean array - true if column is in PK */
};

................................................................................
        assert( op2==SQLITE_INSERT );
        pNew->op = SQLITE_UPDATE;
        if( 0==sessionMergeUpdate(&aCsr, pTab, pExist->aRecord, 0, aRec, 0) ){
          sqlite3_free(pNew);
          pNew = 0;
        }
      }else if( op2==SQLITE_UPDATE ){       /* UPDATE + UPDATE */

        u8 *a1 = pExist->aRecord;
        u8 *a2 = aRec;
        assert( op1==SQLITE_UPDATE );
        sessionReadRecord(&a1, pTab->nCol, 0);
        sessionReadRecord(&a2, pTab->nCol, 0);
        pNew->op = SQLITE_UPDATE;
        if( 0==sessionMergeUpdate(&aCsr, pTab, aRec, pExist->aRecord, a1, a2) ){
          sqlite3_free(pNew);
          pNew = 0;
        }

** on the *ppOut pointer to free the buffer allocation following a successful 
** call to this function.
**
** WARNING/TODO: This function currently assumes that the input is a valid
** changeset. If it is not, the results are undefined.
*/
int sqlite3changeset_invert(
  int nIn, void *pIn,             /* Input changeset */
  int *pnOut, void **ppOut        /* OUT: Inverse of input */
);

/*
** CAPI3REF: Concatenate Two Changeset Objects
**
** This function is used to concatenate two changesets, A and B, into a 

** on the *ppOut pointer to free the buffer allocation following a successful 
** call to this function.
**
** WARNING/TODO: This function currently assumes that the input is a valid
** changeset. If it is not, the results are undefined.
*/
int sqlite3changeset_invert(
  int nIn, const void *pIn,       /* Input changeset */
  int *pnOut, void **ppOut        /* OUT: Inverse of input */
);

/*
** CAPI3REF: Concatenate Two Changeset Objects
**
** This function is used to concatenate two changesets, A and B, into a