}
  if( pDest->nCol!=pSrc->nCol ){
    return 0;   /* Number of columns must be the same in tab1 and tab2 */
  }
  if( pDest->iPKey!=pSrc->iPKey ){
    return 0;   /* Both tables must have the same INTEGER PRIMARY KEY */
  }
  if( HasRowid(pDest)!=HasRowid(pSrc) ){
    return 0;   /* source and destination must both be WITHOUT ROWID or not */
  }
  for(i=0; i<pDest->nCol; i++){
    if( pDest->aCol[i].affinity!=pSrc->aCol[i].affinity ){
      return 0;    /* Affinity must be the same on all columns */
    }
    if( !xferCompatibleCollation(pDest->aCol[i].zColl, pSrc->aCol[i].zColl) ){
      return 0;    /* Collating sequence must be the same on all columns */
    }
................................................................................
  v = sqlite3GetVdbe(pParse);
  sqlite3CodeVerifySchema(pParse, iDbSrc);
  iSrc = pParse->nTab++;
  iDest = pParse->nTab++;
  regAutoinc = autoIncBegin(pParse, iDbDest, pDest);
  regData = sqlite3GetTempReg(pParse);
  regRowid = sqlite3GetTempReg(pParse);
  if( HasRowid(pSrc) ){
    sqlite3OpenTable(pParse, iDest, iDbDest, pDest, OP_OpenWrite);

    if( (pDest->iPKey<0 && pDest->pIndex!=0)          /* (1) */
     || destHasUniqueIdx                              /* (2) */
     || (onError!=OE_Abort && onError!=OE_Rollback)   /* (3) */
    ){
      /* In some circumstances, we are able to run the xfer optimization
      ** only if the destination table is initially empty.  This code makes
      ** that determination.  Conditions under which the destination must
      ** be empty:
      **
      ** (1) There is no INTEGER PRIMARY KEY but there are indices.
      **     (If the destination is not initially empty, the rowid fields
      **     of index entries might need to change.)
      **
      ** (2) The destination has a unique index.  (The xfer optimization 
      **     is unable to test uniqueness.)
      **
      ** (3) onError is something other than OE_Abort and OE_Rollback.
      */
      addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iDest, 0);
      emptyDestTest = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
      sqlite3VdbeJumpHere(v, addr1);
    }else{
      emptyDestTest = 0;
    }

    sqlite3OpenTable(pParse, iSrc, iDbSrc, pSrc, OP_OpenRead);
    emptySrcTest = sqlite3VdbeAddOp2(v, OP_Rewind, iSrc, 0);
    if( pDest->iPKey>=0 ){
      addr1 = sqlite3VdbeAddOp2(v, OP_Rowid, iSrc, regRowid);
      addr2 = sqlite3VdbeAddOp3(v, OP_NotExists, iDest, 0, regRowid);
      sqlite3RowidConstraint(pParse, onError, pDest);
      sqlite3VdbeJumpHere(v, addr2);

  }
  if( pDest->nCol!=pSrc->nCol ){
    return 0;   /* Number of columns must be the same in tab1 and tab2 */
  }
  if( pDest->iPKey!=pSrc->iPKey ){
    return 0;   /* Both tables must have the same INTEGER PRIMARY KEY */
  }



  for(i=0; i<pDest->nCol; i++){
    if( pDest->aCol[i].affinity!=pSrc->aCol[i].affinity ){
      return 0;    /* Affinity must be the same on all columns */
    }
    if( !xferCompatibleCollation(pDest->aCol[i].zColl, pSrc->aCol[i].zColl) ){
      return 0;    /* Collating sequence must be the same on all columns */
    }
................................................................................
  v = sqlite3GetVdbe(pParse);
  sqlite3CodeVerifySchema(pParse, iDbSrc);
  iSrc = pParse->nTab++;
  iDest = pParse->nTab++;
  regAutoinc = autoIncBegin(pParse, iDbDest, pDest);
  regData = sqlite3GetTempReg(pParse);
  regRowid = sqlite3GetTempReg(pParse);

  sqlite3OpenTable(pParse, iDest, iDbDest, pDest, OP_OpenWrite);
  assert( HasRowid(pDest) || destHasUniqueIdx );
  if( (pDest->iPKey<0 && pDest->pIndex!=0)          /* (1) */
   || destHasUniqueIdx                              /* (2) */
   || (onError!=OE_Abort && onError!=OE_Rollback)   /* (3) */
  ){
    /* In some circumstances, we are able to run the xfer optimization
    ** only if the destination table is initially empty.  This code makes
    ** that determination.  Conditions under which the destination must
    ** be empty:
    **
    ** (1) There is no INTEGER PRIMARY KEY but there are indices.
    **     (If the destination is not initially empty, the rowid fields
    **     of index entries might need to change.)
    **
    ** (2) The destination has a unique index.  (The xfer optimization 
    **     is unable to test uniqueness.)
    **
    ** (3) onError is something other than OE_Abort and OE_Rollback.
    */
    addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iDest, 0);
    emptyDestTest = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
    sqlite3VdbeJumpHere(v, addr1);


  }
  if( HasRowid(pSrc) ){
    sqlite3OpenTable(pParse, iSrc, iDbSrc, pSrc, OP_OpenRead);
    emptySrcTest = sqlite3VdbeAddOp2(v, OP_Rewind, iSrc, 0);
    if( pDest->iPKey>=0 ){
      addr1 = sqlite3VdbeAddOp2(v, OP_Rowid, iSrc, regRowid);
      addr2 = sqlite3VdbeAddOp3(v, OP_NotExists, iDest, 0, regRowid);
      sqlite3RowidConstraint(pParse, onError, pDest);
      sqlite3VdbeJumpHere(v, addr2);

}

proc explain_i {sql {db db}} {
  puts ""
  puts "addr  opcode        p1      p2      p3      p4                p5  #"
  puts "----  ------------  ------  ------  ------  ----------------  --  -"

  set addrTail 0


  $db eval "explain $sql" {} {
    set x($addr) 0
    set op($addr) $opcode

    if {$opcode == "Goto" && $addrTail==0} {
      set addrTail $p2

    }

    if {$opcode == "Next"} {
      for {set i $p2} {$i<$addr} {incr i} {
        incr x($i) 2
      }
    }

    if {$opcode == "Goto" && $p2<$addr && $op($p2)=="Yield"} {
      for {set i [expr $p2+1]} {$i<$addr} {incr i} {
        incr x($i) 2
      }
    }




  }

  $db eval "explain $sql" {} {
    if {$addr == $addrTail} {
      puts ""
    }
    set I [string repeat " " $x($addr)]
    puts [format {%-4d  %s%-12.12s  %-6d  %-6d  %-6d  % -17s %s  %s} \
      $addr $I $opcode $p1 $p2 $p3 $p4 $p5 $comment
    ]

    if {$opcode == "Halt" && $comment == "End of coroutine"} {
      puts ""
    }
  }
  puts "----  ------------  ------  ------  ------  ----------------  --  -"
}

# Show the VDBE program for an SQL statement but omit the Trace
# opcode at the beginning.  This procedure can be used to prove
# that different SQL statements generate exactly the same VDBE code.

}

proc explain_i {sql {db db}} {
  puts ""
  puts "addr  opcode        p1      p2      p3      p4                p5  #"
  puts "----  ------------  ------  ------  ------  ----------------  --  -"



  set bSeenGoto 0
  $db eval "explain $sql" {} {
    set x($addr) 0
    set op($addr) $opcode

    if {$opcode == "Goto" && ($bSeenGoto==0 || ($p2 > $addr+10))} {
      set linebreak($p2) 1
      set bSeenGoto 1
    }

    if {$opcode == "Next"} {
      for {set i $p2} {$i<$addr} {incr i} {
        incr x($i) 2
      }
    }

    if {$opcode == "Goto" && $p2<$addr && $op($p2)=="Yield"} {
      for {set i [expr $p2+1]} {$i<$addr} {incr i} {
        incr x($i) 2
      }
    }

    if {$opcode == "Halt" && $comment == "End of coroutine"} {
      set linebreak([expr $addr+1]) 1
    }
  }

  $db eval "explain $sql" {} {
    if {[info exists linebreak($addr)]} {
      puts ""
    }
    set I [string repeat " " $x($addr)]
    puts [format {%-4d  %s%-12.12s  %-6d  %-6d  %-6d  % -17s %s  %s} \
      $addr $I $opcode $p1 $p2 $p3 $p4 $p5 $comment
    ]




  }
  puts "----  ------------  ------  ------  ------  ----------------  --  -"
}

# Show the VDBE program for an SQL statement but omit the Trace
# opcode at the beginning.  This procedure can be used to prove
# that different SQL statements generate exactly the same VDBE code.

} {}

do_execsql_test 2.4.2 {
  SELECT * FROM t6 ORDER BY b, a;
  SELECT * FROM t6 ORDER BY c;
} {ABC def ghi ABC def ghi}



















































finish_test

} {}

do_execsql_test 2.4.2 {
  SELECT * FROM t6 ORDER BY b, a;
  SELECT * FROM t6 ORDER BY c;
} {ABC def ghi ABC def ghi}

#-------------------------------------------------------------------------
# Unless the destination table is completely empty, the xfer optimization 
# is disabled for WITHOUT ROWID tables. The following tests check for
# some problems that might occur if this were not the case.
#
reset_db
do_execsql_test 3.1.1 {
  CREATE TABLE t1(a, b, PRIMARY KEY(a)) WITHOUT ROWID;
  CREATE UNIQUE INDEX i1 ON t1(b);

  CREATE TABLE t2(a, b, PRIMARY KEY(a)) WITHOUT ROWID;
  CREATE UNIQUE INDEX i2 ON t2(b);

  INSERT INTO t1 VALUES('one', 'two');
  INSERT INTO t2 VALUES('three', 'two');
}

do_execsql_test 3.1.2 {
  INSERT OR REPLACE INTO t1 SELECT * FROM t2;
  SELECT * FROM t1;
} {three two}

do_execsql_test 3.1.3 {
  DELETE FROM t1;
  INSERT INTO t1 SELECT * FROM t2;
  SELECT * FROM t1;
} {three two}

do_catchsql_test 3.1.4 {
  INSERT INTO t2 VALUES('four', 'four');
  INSERT INTO t2 VALUES('six', 'two');
  INSERT INTO t1 SELECT * FROM t2;
} {1 {UNIQUE constraint failed: t2.b}}

do_execsql_test 3.1.5 {
  CREATE TABLE t3(a PRIMARY KEY);
  CREATE TABLE t4(a PRIMARY KEY);

  INSERT INTO t4 VALUES('i');
  INSERT INTO t4 VALUES('ii');
  INSERT INTO t4 VALUES('iii');

  INSERT INTO t3 SELECT * FROM t4;
  SELECT * FROM t3;
} {i ii iii}
  
  explain_i {
  INSERT INTO t3 SELECT * FROM t4;
  }

finish_test