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Overview
Comment:Remove the out2-prerelease VDBE opcode property and its associated code, for a 0.5% performance improvement.
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SHA1:e29c7f2c910dac07f0f92dfef5e0e743141954eb
User & Date: drh 2015-04-13 19:14:06
Context
2015-04-13
21:39
Omit the "pc" or "program counter" variable from the VDBE loop for 0.6% performance increase. check-in: d2f10c41 user: drh tags: trunk
19:14
Remove the out2-prerelease VDBE opcode property and its associated code, for a 0.5% performance improvement. check-in: e29c7f2c user: drh tags: trunk
17:43
Add a comment to wal.c to explain why a race condition is safe. check-in: bc33af86 user: dan tags: trunk
Changes
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Changes to mkopcodeh.awk.

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# Scan for "case OP_aaaa:" lines in the vdbe.c file
/^case OP_/ {
  name = $2
  sub(/:/,"",name)
  sub("\r","",name)
  op[name] = -1       # op[x] holds the numeric value for OP symbol x
  jump[name] = 0
  out2_prerelease[name] = 0
  in1[name] = 0
  in2[name] = 0
  in3[name] = 0
  out2[name] = 0
  out3[name] = 0
  for(i=3; i<NF; i++){
    if($i=="same" && $(i+1)=="as"){
................................................................................
      sameas[val] = sym
      def[val] = name
    }
    x = $i
    sub(",","",x)
    if(x=="jump"){
      jump[name] = 1
    }else if(x=="out2-prerelease"){
      out2_prerelease[name] = 1
    }else if(x=="in1"){
      in1[name] = 1
    }else if(x=="in2"){
      in2[name] = 1
    }else if(x=="in3"){
      in3[name] = 1
    }else if(x=="out2"){
................................................................................
  #  bit 1:     pushes a result onto stack
  #  bit 2:     output to p1.  release p1 before opcode runs
  #
  for(i=0; i<=max; i++){
    name = def[i]
    a0 = a1 = a2 = a3 = a4 = a5 = a6 = a7 = 0
    if( jump[name] ) a0 = 1;
    if( out2_prerelease[name] ) a1 = 2;
    if( in1[name] ) a2 = 4;
    if( in2[name] ) a3 = 8;
    if( in3[name] ) a4 = 16;
    if( out2[name] ) a5 = 32;
    if( out3[name] ) a6 = 64;
    bv[i] = a0+a1+a2+a3+a4+a5+a6+a7;
  }
  print "\n"
  print "/* Properties such as \"out2\" or \"jump\" that are specified in"
  print "** comments following the \"case\" for each opcode in the vdbe.c"
  print "** are encoded into bitvectors as follows:"
  print "*/"
  print "#define OPFLG_JUMP            0x0001  /* jump:  P2 holds jmp target */"
  print "#define OPFLG_OUT2_PRERELEASE 0x0002  /* out2-prerelease: */"
  print "#define OPFLG_IN1             0x0004  /* in1:   P1 is an input */"
  print "#define OPFLG_IN2             0x0008  /* in2:   P2 is an input */"
  print "#define OPFLG_IN3             0x0010  /* in3:   P3 is an input */"
  print "#define OPFLG_OUT2            0x0020  /* out2:  P2 is an output */"
  print "#define OPFLG_OUT3            0x0040  /* out3:  P3 is an output */"
  print "#define OPFLG_INITIALIZER {\\"
  for(i=0; i<=max; i++){
    if( i%8==0 ) printf("/* %3d */",i)
    printf " 0x%02x,", bv[i]
    if( i%8==7 ) printf("\\\n");
  }
  print "}"







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# Scan for "case OP_aaaa:" lines in the vdbe.c file
/^case OP_/ {
  name = $2
  sub(/:/,"",name)
  sub("\r","",name)
  op[name] = -1       # op[x] holds the numeric value for OP symbol x
  jump[name] = 0

  in1[name] = 0
  in2[name] = 0
  in3[name] = 0
  out2[name] = 0
  out3[name] = 0
  for(i=3; i<NF; i++){
    if($i=="same" && $(i+1)=="as"){
................................................................................
      sameas[val] = sym
      def[val] = name
    }
    x = $i
    sub(",","",x)
    if(x=="jump"){
      jump[name] = 1


    }else if(x=="in1"){
      in1[name] = 1
    }else if(x=="in2"){
      in2[name] = 1
    }else if(x=="in3"){
      in3[name] = 1
    }else if(x=="out2"){
................................................................................
  #  bit 1:     pushes a result onto stack
  #  bit 2:     output to p1.  release p1 before opcode runs
  #
  for(i=0; i<=max; i++){
    name = def[i]
    a0 = a1 = a2 = a3 = a4 = a5 = a6 = a7 = 0
    if( jump[name] ) a0 = 1;

    if( in1[name] ) a2 = 2;
    if( in2[name] ) a3 = 4;
    if( in3[name] ) a4 = 8;
    if( out2[name] ) a5 = 16;
    if( out3[name] ) a6 = 32;
    bv[i] = a0+a1+a2+a3+a4+a5+a6;
  }
  print "\n"
  print "/* Properties such as \"out2\" or \"jump\" that are specified in"
  print "** comments following the \"case\" for each opcode in the vdbe.c"
  print "** are encoded into bitvectors as follows:"
  print "*/"
  print "#define OPFLG_JUMP            0x0001  /* jump:  P2 holds jmp target */"

  print "#define OPFLG_IN1             0x0002  /* in1:   P1 is an input */"
  print "#define OPFLG_IN2             0x0004  /* in2:   P2 is an input */"
  print "#define OPFLG_IN3             0x0008  /* in3:   P3 is an input */"
  print "#define OPFLG_OUT2            0x0010  /* out2:  P2 is an output */"
  print "#define OPFLG_OUT3            0x0020  /* out3:  P3 is an output */"
  print "#define OPFLG_INITIALIZER {\\"
  for(i=0; i<=max; i++){
    if( i%8==0 ) printf("/* %3d */",i)
    printf " 0x%02x,", bv[i]
    if( i%8==7 ) printf("\\\n");
  }
  print "}"

Changes to src/vdbe.c.

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  Savepoint *p;
  for(p=db->pSavepoint; p; p=p->pNext) n++;
  assert( n==(db->nSavepoint + db->isTransactionSavepoint) );
  return 1;
}
#endif

















/*
** Execute as much of a VDBE program as we can.
** This is the core of sqlite3_step().  
*/
int sqlite3VdbeExec(
  Vdbe *p                    /* The VDBE */
................................................................................
      sqlite3_interrupt_count--;
      if( sqlite3_interrupt_count==0 ){
        sqlite3_interrupt(db);
      }
    }
#endif

    /* On any opcode with the "out2-prerelease" tag, free any
    ** external allocations out of mem[p2] and set mem[p2] to be
    ** an undefined integer.  Opcodes will either fill in the integer
    ** value or convert mem[p2] to a different type.
    */
    assert( pOp->opflags==sqlite3OpcodeProperty[pOp->opcode] );
    if( pOp->opflags & OPFLG_OUT2_PRERELEASE ){
      assert( pOp->p2>0 );
      assert( pOp->p2<=(p->nMem-p->nCursor) );
      pOut = &aMem[pOp->p2];
      memAboutToChange(p, pOut);
      if( VdbeMemDynamic(pOut) ) sqlite3VdbeMemSetNull(pOut);
      pOut->flags = MEM_Int;
    }

    /* Sanity checking on other operands */
#ifdef SQLITE_DEBUG

    if( (pOp->opflags & OPFLG_IN1)!=0 ){
      assert( pOp->p1>0 );
      assert( pOp->p1<=(p->nMem-p->nCursor) );
      assert( memIsValid(&aMem[pOp->p1]) );
      assert( sqlite3VdbeCheckMemInvariants(&aMem[pOp->p1]) );
      REGISTER_TRACE(pOp->p1, &aMem[pOp->p1]);
    }
................................................................................
** opcode and the opcodes.c file is filled with an array of strings where
** each string is the symbolic name for the corresponding opcode.  If the
** case statement is followed by a comment of the form "/# same as ... #/"
** that comment is used to determine the particular value of the opcode.
**
** Other keywords in the comment that follows each case are used to
** construct the OPFLG_INITIALIZER value that initializes opcodeProperty[].
** Keywords include: in1, in2, in3, out2_prerelease, out2, out3.  See
** the mkopcodeh.awk script for additional information.
**
** Documentation about VDBE opcodes is generated by scanning this file
** for lines of that contain "Opcode:".  That line and all subsequent
** comment lines are used in the generation of the opcode.html documentation
** file.
**
................................................................................
}

/* Opcode: Integer P1 P2 * * *
** Synopsis: r[P2]=P1
**
** The 32-bit integer value P1 is written into register P2.
*/
case OP_Integer: {         /* out2-prerelease */

  pOut->u.i = pOp->p1;
  break;
}

/* Opcode: Int64 * P2 * P4 *
** Synopsis: r[P2]=P4
**
** P4 is a pointer to a 64-bit integer value.
** Write that value into register P2.
*/
case OP_Int64: {           /* out2-prerelease */

  assert( pOp->p4.pI64!=0 );
  pOut->u.i = *pOp->p4.pI64;
  break;
}

#ifndef SQLITE_OMIT_FLOATING_POINT
/* Opcode: Real * P2 * P4 *
** Synopsis: r[P2]=P4
**
** P4 is a pointer to a 64-bit floating point value.
** Write that value into register P2.
*/
case OP_Real: {            /* same as TK_FLOAT, out2-prerelease */

  pOut->flags = MEM_Real;
  assert( !sqlite3IsNaN(*pOp->p4.pReal) );
  pOut->u.r = *pOp->p4.pReal;
  break;
}
#endif

................................................................................
** Synopsis: r[P2]='P4'
**
** P4 points to a nul terminated UTF-8 string. This opcode is transformed 
** into a String opcode before it is executed for the first time.  During
** this transformation, the length of string P4 is computed and stored
** as the P1 parameter.
*/
case OP_String8: {         /* same as TK_STRING, out2-prerelease */
  assert( pOp->p4.z!=0 );

  pOp->opcode = OP_String;
  pOp->p1 = sqlite3Strlen30(pOp->p4.z);

#ifndef SQLITE_OMIT_UTF16
  if( encoding!=SQLITE_UTF8 ){
    rc = sqlite3VdbeMemSetStr(pOut, pOp->p4.z, -1, SQLITE_UTF8, SQLITE_STATIC);
    if( rc==SQLITE_TOOBIG ) goto too_big;
................................................................................
** The string value P4 of length P1 (bytes) is stored in register P2.
**
** If P5!=0 and the content of register P3 is greater than zero, then
** the datatype of the register P2 is converted to BLOB.  The content is
** the same sequence of bytes, it is merely interpreted as a BLOB instead
** of a string, as if it had been CAST.
*/
case OP_String: {          /* out2-prerelease */
  assert( pOp->p4.z!=0 );

  pOut->flags = MEM_Str|MEM_Static|MEM_Term;
  pOut->z = pOp->p4.z;
  pOut->n = pOp->p1;
  pOut->enc = encoding;
  UPDATE_MAX_BLOBSIZE(pOut);
  if( pOp->p5 ){
    assert( pOp->p3>0 );
................................................................................
** is less than P2 (typically P3 is zero) then only register P2 is
** set to NULL.
**
** If the P1 value is non-zero, then also set the MEM_Cleared flag so that
** NULL values will not compare equal even if SQLITE_NULLEQ is set on
** OP_Ne or OP_Eq.
*/
case OP_Null: {           /* out2-prerelease */
  int cnt;
  u16 nullFlag;

  cnt = pOp->p3-pOp->p2;
  assert( pOp->p3<=(p->nMem-p->nCursor) );
  pOut->flags = nullFlag = pOp->p1 ? (MEM_Null|MEM_Cleared) : MEM_Null;
  while( cnt>0 ){
    pOut++;
    memAboutToChange(p, pOut);
    sqlite3VdbeMemSetNull(pOut);
................................................................................

/* Opcode: Blob P1 P2 * P4 *
** Synopsis: r[P2]=P4 (len=P1)
**
** P4 points to a blob of data P1 bytes long.  Store this
** blob in register P2.
*/
case OP_Blob: {                /* out2-prerelease */
  assert( pOp->p1 <= SQLITE_MAX_LENGTH );

  sqlite3VdbeMemSetStr(pOut, pOp->p4.z, pOp->p1, 0, 0);
  pOut->enc = encoding;
  UPDATE_MAX_BLOBSIZE(pOut);
  break;
}

/* Opcode: Variable P1 P2 * P4 *
................................................................................
** Synopsis: r[P2]=parameter(P1,P4)
**
** Transfer the values of bound parameter P1 into register P2
**
** If the parameter is named, then its name appears in P4.
** The P4 value is used by sqlite3_bind_parameter_name().
*/
case OP_Variable: {            /* out2-prerelease */
  Mem *pVar;       /* Value being transferred */

  assert( pOp->p1>0 && pOp->p1<=p->nVar );
  assert( pOp->p4.z==0 || pOp->p4.z==p->azVar[pOp->p1-1] );
  pVar = &p->aVar[pOp->p1 - 1];
  if( sqlite3VdbeMemTooBig(pVar) ){
    goto too_big;
  }

  sqlite3VdbeMemShallowCopy(pOut, pVar, MEM_Static);
  UPDATE_MAX_BLOBSIZE(pOut);
  break;
}

/* Opcode: Move P1 P2 P3 * *
** Synopsis:  r[P2@P3]=r[P1@P3]
................................................................................
/* Opcode: Count P1 P2 * * *
** Synopsis: r[P2]=count()
**
** Store the number of entries (an integer value) in the table or index 
** opened by cursor P1 in register P2
*/
#ifndef SQLITE_OMIT_BTREECOUNT
case OP_Count: {         /* out2-prerelease */
  i64 nEntry;
  BtCursor *pCrsr;

  pCrsr = p->apCsr[pOp->p1]->pCursor;
  assert( pCrsr );
  nEntry = 0;  /* Not needed.  Only used to silence a warning. */
  rc = sqlite3BtreeCount(pCrsr, &nEntry);

  pOut->u.i = nEntry;
  break;
}
#endif

/* Opcode: Savepoint P1 * * P4 *
**
................................................................................
** the main database file and P1==1 is the database file used to store
** temporary tables.
**
** There must be a read-lock on the database (either a transaction
** must be started or there must be an open cursor) before
** 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( DbMaskTest(p->btreeMask, iDb) );

  sqlite3BtreeGetMeta(db->aDb[iDb].pBt, iCookie, (u32 *)&iMeta);

  pOut->u.i = iMeta;
  break;
}

/* Opcode: SetCookie P1 P2 P3 * *
**
** Write the content of register P3 (interpreted as an integer)
................................................................................
** Synopsis: r[P2]=cursor[P1].ctr++
**
** Find the next available sequence number for cursor P1.
** Write the sequence number into register P2.
** The sequence number on the cursor is incremented after this
** instruction.  
*/
case OP_Sequence: {           /* out2-prerelease */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( p->apCsr[pOp->p1]!=0 );

  pOut->u.i = p->apCsr[pOp->p1]->seqCount++;
  break;
}


/* Opcode: NewRowid P1 P2 P3 * *
** Synopsis: r[P2]=rowid
................................................................................
** If P3>0 then P3 is a register in the root frame of this VDBE that holds 
** the largest previously generated record number. No new record numbers are
** allowed to be less than this value. When this value reaches its maximum, 
** an SQLITE_FULL error is generated. The P3 register is updated with the '
** generated record number. This P3 mechanism is used to help implement the
** AUTOINCREMENT feature.
*/
case OP_NewRowid: {           /* out2-prerelease */
  i64 v;                 /* The new rowid */
  VdbeCursor *pC;        /* Cursor of table to get the new rowid */
  int res;               /* Result of an sqlite3BtreeLast() */
  int cnt;               /* Counter to limit the number of searches */
  Mem *pMem;             /* Register holding largest rowid for AUTOINCREMENT */
  VdbeFrame *pFrame;     /* Root frame of VDBE */

  v = 0;
  res = 0;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  if( NEVER(pC->pCursor==0) ){
    /* The zero initialization above is all that is needed */
  }else{
    /* The next rowid or record number (different terms for the same
................................................................................
** Store in register P2 an integer which is the key of the table entry that
** P1 is currently point to.
**
** P1 can be either an ordinary table or a virtual table.  There used to
** be a separate OP_VRowid opcode for use with virtual tables, but this
** one opcode now works for both table types.
*/
case OP_Rowid: {                 /* out2-prerelease */
  VdbeCursor *pC;
  i64 v;
  sqlite3_vtab *pVtab;
  const sqlite3_module *pModule;


  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->pseudoTableReg==0 || pC->nullRow );
  if( pC->nullRow ){
    pOut->flags = MEM_Null;
    break;
................................................................................
**
** Write into register P2 an integer which is the last entry in the record at
** the end of the index key pointed to by cursor P1.  This integer should be
** the rowid of the table entry to which this index entry points.
**
** See also: Rowid, MakeRecord.
*/
case OP_IdxRowid: {              /* out2-prerelease */
  BtCursor *pCrsr;
  VdbeCursor *pC;
  i64 rowid;


  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  pCrsr = pC->pCursor;
  assert( pCrsr!=0 );
  pOut->flags = MEM_Null;
  assert( pC->isTable==0 );
................................................................................
** is stored in register P2.  If no page 
** movement was required (because the table being dropped was already 
** the last one in the database) then a zero is stored in register P2.
** If AUTOVACUUM is disabled then a zero is stored in register P2.
**
** See also: Clear
*/
case OP_Destroy: {     /* out2-prerelease */
  int iMoved;
  int iDb;

  assert( p->readOnly==0 );

  pOut->flags = MEM_Null;
  if( db->nVdbeRead > db->nVDestroy+1 ){
    rc = SQLITE_LOCKED;
    p->errorAction = OE_Abort;
  }else{
    iDb = pOp->p3;
    assert( DbMaskTest(p->btreeMask, iDb) );
................................................................................
** Allocate a new index in the main database file if P1==0 or in the
** auxiliary database file if P1==1 or in an attached database if
** P1>1.  Write the root page number of the new table into
** register P2.
**
** See documentation on OP_CreateTable for additional information.
*/
case OP_CreateIndex:            /* out2-prerelease */
case OP_CreateTable: {          /* out2-prerelease */
  int pgno;
  int flags;
  Db *pDb;


  pgno = 0;
  assert( pOp->p1>=0 && pOp->p1<db->nDb );
  assert( DbMaskTest(p->btreeMask, pOp->p1) );
  assert( p->readOnly==0 );
  pDb = &db->aDb[pOp->p1];
  assert( pDb->pBt!=0 );
  if( pOp->opcode==OP_CreateTable ){
................................................................................
** address space. This is used by trigger programs to access the new.* 
** and old.* values.
**
** The address of the cell in the parent frame is determined by adding
** the value of the P1 argument to the value of the P1 argument to the
** calling OP_Program instruction.
*/
case OP_Param: {           /* out2-prerelease */
  VdbeFrame *pFrame;
  Mem *pIn;

  pFrame = p->pFrame;
  pIn = &pFrame->aMem[pOp->p1 + pFrame->aOp[pFrame->pc].p1];   
  sqlite3VdbeMemShallowCopy(pOut, pIn, MEM_Ephem);
  break;
}

#endif /* #ifndef SQLITE_OMIT_TRIGGER */
................................................................................
** modes (delete, truncate, persist, off and memory), this is a simple
** operation. No IO is required.
**
** If changing into or out of WAL mode the procedure is more complicated.
**
** Write a string containing the final journal-mode to register P2.
*/
case OP_JournalMode: {    /* out2-prerelease */
  Btree *pBt;                     /* Btree to change journal mode of */
  Pager *pPager;                  /* Pager associated with pBt */
  int eNew;                       /* New journal mode */
  int eOld;                       /* The old journal mode */
#ifndef SQLITE_OMIT_WAL
  const char *zFilename;          /* Name of database file for pPager */
#endif


  eNew = pOp->p3;
  assert( eNew==PAGER_JOURNALMODE_DELETE 
       || eNew==PAGER_JOURNALMODE_TRUNCATE 
       || eNew==PAGER_JOURNALMODE_PERSIST 
       || eNew==PAGER_JOURNALMODE_OFF
       || eNew==PAGER_JOURNALMODE_MEMORY
       || eNew==PAGER_JOURNALMODE_WAL
................................................................................
#endif /* SQLITE_OMIT_VIRTUALTABLE */

#ifndef  SQLITE_OMIT_PAGER_PRAGMAS
/* Opcode: Pagecount P1 P2 * * *
**
** Write the current number of pages in database P1 to memory cell P2.
*/
case OP_Pagecount: {            /* out2-prerelease */

  pOut->u.i = sqlite3BtreeLastPage(db->aDb[pOp->p1].pBt);
  break;
}
#endif


#ifndef  SQLITE_OMIT_PAGER_PRAGMAS
................................................................................
**
** Try to set the maximum page count for database P1 to the value in P3.
** Do not let the maximum page count fall below the current page count and
** do not change the maximum page count value if P3==0.
**
** Store the maximum page count after the change in register P2.
*/
case OP_MaxPgcnt: {            /* out2-prerelease */
  unsigned int newMax;
  Btree *pBt;


  pBt = db->aDb[pOp->p1].pBt;
  newMax = 0;
  if( pOp->p3 ){
    newMax = sqlite3BtreeLastPage(pBt);
    if( newMax < (unsigned)pOp->p3 ) newMax = (unsigned)pOp->p3;
  }
  pOut->u.i = sqlite3BtreeMaxPageCount(pBt, newMax);
................................................................................
    */
#ifndef NDEBUG
    assert( pc>=-1 && pc<p->nOp );

#ifdef SQLITE_DEBUG
    if( db->flags & SQLITE_VdbeTrace ){
      if( rc!=0 ) printf("rc=%d\n",rc);
      if( pOp->opflags & (OPFLG_OUT2_PRERELEASE|OPFLG_OUT2) ){
        registerTrace(pOp->p2, &aMem[pOp->p2]);
      }
      if( pOp->opflags & OPFLG_OUT3 ){
        registerTrace(pOp->p3, &aMem[pOp->p3]);
      }
    }
#endif  /* SQLITE_DEBUG */







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660
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702
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...
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1003
1004
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1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
....
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
....
1058
1059
1060
1061
1062
1063
1064
1065
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1068
1069
1070
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1073
1074
....
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1093
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1100
1101
1102
1103
1104
1105
....
1126
1127
1128
1129
1130
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1132
1133
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1136
1137
1138
1139
1140
1141
1142
....
1143
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....
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....
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3141
3142
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3147
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3151
....
3958
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  Savepoint *p;
  for(p=db->pSavepoint; p; p=p->pNext) n++;
  assert( n==(db->nSavepoint + db->isTransactionSavepoint) );
  return 1;
}
#endif

/*
** Return the register of pOp->p2 after first preparing it to be
** overwritten with an integer value.
*/ 
static Mem *out2Prerelease(Vdbe *p, VdbeOp *pOp){
  Mem *pOut;
  assert( pOp->p2>0 );
  assert( pOp->p2<=(p->nMem-p->nCursor) );
  pOut = &p->aMem[pOp->p2];
  memAboutToChange(p, pOut);
  if( VdbeMemDynamic(pOut) ) sqlite3VdbeMemSetNull(pOut);
  pOut->flags = MEM_Int;
  return pOut;
}


/*
** Execute as much of a VDBE program as we can.
** This is the core of sqlite3_step().  
*/
int sqlite3VdbeExec(
  Vdbe *p                    /* The VDBE */
................................................................................
      sqlite3_interrupt_count--;
      if( sqlite3_interrupt_count==0 ){
        sqlite3_interrupt(db);
      }
    }
#endif
















    /* Sanity checking on other operands */
#ifdef SQLITE_DEBUG
    assert( pOp->opflags==sqlite3OpcodeProperty[pOp->opcode] );
    if( (pOp->opflags & OPFLG_IN1)!=0 ){
      assert( pOp->p1>0 );
      assert( pOp->p1<=(p->nMem-p->nCursor) );
      assert( memIsValid(&aMem[pOp->p1]) );
      assert( sqlite3VdbeCheckMemInvariants(&aMem[pOp->p1]) );
      REGISTER_TRACE(pOp->p1, &aMem[pOp->p1]);
    }
................................................................................
** opcode and the opcodes.c file is filled with an array of strings where
** each string is the symbolic name for the corresponding opcode.  If the
** case statement is followed by a comment of the form "/# same as ... #/"
** that comment is used to determine the particular value of the opcode.
**
** Other keywords in the comment that follows each case are used to
** construct the OPFLG_INITIALIZER value that initializes opcodeProperty[].
** Keywords include: in1, in2, in3, out2, out3.  See
** the mkopcodeh.awk script for additional information.
**
** Documentation about VDBE opcodes is generated by scanning this file
** for lines of that contain "Opcode:".  That line and all subsequent
** comment lines are used in the generation of the opcode.html documentation
** file.
**
................................................................................
}

/* Opcode: Integer P1 P2 * * *
** Synopsis: r[P2]=P1
**
** The 32-bit integer value P1 is written into register P2.
*/
case OP_Integer: {         /* out2 */
  pOut = out2Prerelease(p, pOp);
  pOut->u.i = pOp->p1;
  break;
}

/* Opcode: Int64 * P2 * P4 *
** Synopsis: r[P2]=P4
**
** P4 is a pointer to a 64-bit integer value.
** Write that value into register P2.
*/
case OP_Int64: {           /* out2 */
  pOut = out2Prerelease(p, pOp);
  assert( pOp->p4.pI64!=0 );
  pOut->u.i = *pOp->p4.pI64;
  break;
}

#ifndef SQLITE_OMIT_FLOATING_POINT
/* Opcode: Real * P2 * P4 *
** Synopsis: r[P2]=P4
**
** P4 is a pointer to a 64-bit floating point value.
** Write that value into register P2.
*/
case OP_Real: {            /* same as TK_FLOAT, out2 */
  pOut = out2Prerelease(p, pOp);
  pOut->flags = MEM_Real;
  assert( !sqlite3IsNaN(*pOp->p4.pReal) );
  pOut->u.r = *pOp->p4.pReal;
  break;
}
#endif

................................................................................
** Synopsis: r[P2]='P4'
**
** P4 points to a nul terminated UTF-8 string. This opcode is transformed 
** into a String opcode before it is executed for the first time.  During
** this transformation, the length of string P4 is computed and stored
** as the P1 parameter.
*/
case OP_String8: {         /* same as TK_STRING, out2 */
  assert( pOp->p4.z!=0 );
  pOut = out2Prerelease(p, pOp);
  pOp->opcode = OP_String;
  pOp->p1 = sqlite3Strlen30(pOp->p4.z);

#ifndef SQLITE_OMIT_UTF16
  if( encoding!=SQLITE_UTF8 ){
    rc = sqlite3VdbeMemSetStr(pOut, pOp->p4.z, -1, SQLITE_UTF8, SQLITE_STATIC);
    if( rc==SQLITE_TOOBIG ) goto too_big;
................................................................................
** The string value P4 of length P1 (bytes) is stored in register P2.
**
** If P5!=0 and the content of register P3 is greater than zero, then
** the datatype of the register P2 is converted to BLOB.  The content is
** the same sequence of bytes, it is merely interpreted as a BLOB instead
** of a string, as if it had been CAST.
*/
case OP_String: {          /* out2 */
  assert( pOp->p4.z!=0 );
  pOut = out2Prerelease(p, pOp);
  pOut->flags = MEM_Str|MEM_Static|MEM_Term;
  pOut->z = pOp->p4.z;
  pOut->n = pOp->p1;
  pOut->enc = encoding;
  UPDATE_MAX_BLOBSIZE(pOut);
  if( pOp->p5 ){
    assert( pOp->p3>0 );
................................................................................
** is less than P2 (typically P3 is zero) then only register P2 is
** set to NULL.
**
** If the P1 value is non-zero, then also set the MEM_Cleared flag so that
** NULL values will not compare equal even if SQLITE_NULLEQ is set on
** OP_Ne or OP_Eq.
*/
case OP_Null: {           /* out2 */
  int cnt;
  u16 nullFlag;
  pOut = out2Prerelease(p, pOp);
  cnt = pOp->p3-pOp->p2;
  assert( pOp->p3<=(p->nMem-p->nCursor) );
  pOut->flags = nullFlag = pOp->p1 ? (MEM_Null|MEM_Cleared) : MEM_Null;
  while( cnt>0 ){
    pOut++;
    memAboutToChange(p, pOut);
    sqlite3VdbeMemSetNull(pOut);
................................................................................

/* Opcode: Blob P1 P2 * P4 *
** Synopsis: r[P2]=P4 (len=P1)
**
** P4 points to a blob of data P1 bytes long.  Store this
** blob in register P2.
*/
case OP_Blob: {                /* out2 */
  assert( pOp->p1 <= SQLITE_MAX_LENGTH );
  pOut = out2Prerelease(p, pOp);
  sqlite3VdbeMemSetStr(pOut, pOp->p4.z, pOp->p1, 0, 0);
  pOut->enc = encoding;
  UPDATE_MAX_BLOBSIZE(pOut);
  break;
}

/* Opcode: Variable P1 P2 * P4 *
................................................................................
** Synopsis: r[P2]=parameter(P1,P4)
**
** Transfer the values of bound parameter P1 into register P2
**
** If the parameter is named, then its name appears in P4.
** The P4 value is used by sqlite3_bind_parameter_name().
*/
case OP_Variable: {            /* out2 */
  Mem *pVar;       /* Value being transferred */

  assert( pOp->p1>0 && pOp->p1<=p->nVar );
  assert( pOp->p4.z==0 || pOp->p4.z==p->azVar[pOp->p1-1] );
  pVar = &p->aVar[pOp->p1 - 1];
  if( sqlite3VdbeMemTooBig(pVar) ){
    goto too_big;
  }
  pOut = out2Prerelease(p, pOp);
  sqlite3VdbeMemShallowCopy(pOut, pVar, MEM_Static);
  UPDATE_MAX_BLOBSIZE(pOut);
  break;
}

/* Opcode: Move P1 P2 P3 * *
** Synopsis:  r[P2@P3]=r[P1@P3]
................................................................................
/* Opcode: Count P1 P2 * * *
** Synopsis: r[P2]=count()
**
** Store the number of entries (an integer value) in the table or index 
** opened by cursor P1 in register P2
*/
#ifndef SQLITE_OMIT_BTREECOUNT
case OP_Count: {         /* out2 */
  i64 nEntry;
  BtCursor *pCrsr;

  pCrsr = p->apCsr[pOp->p1]->pCursor;
  assert( pCrsr );
  nEntry = 0;  /* Not needed.  Only used to silence a warning. */
  rc = sqlite3BtreeCount(pCrsr, &nEntry);
  pOut = out2Prerelease(p, pOp);
  pOut->u.i = nEntry;
  break;
}
#endif

/* Opcode: Savepoint P1 * * P4 *
**
................................................................................
** the main database file and P1==1 is the database file used to store
** temporary tables.
**
** There must be a read-lock on the database (either a transaction
** must be started or there must be an open cursor) before
** executing this instruction.
*/
case OP_ReadCookie: {               /* out2 */
  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( DbMaskTest(p->btreeMask, iDb) );

  sqlite3BtreeGetMeta(db->aDb[iDb].pBt, iCookie, (u32 *)&iMeta);
  pOut = out2Prerelease(p, pOp);
  pOut->u.i = iMeta;
  break;
}

/* Opcode: SetCookie P1 P2 P3 * *
**
** Write the content of register P3 (interpreted as an integer)
................................................................................
** Synopsis: r[P2]=cursor[P1].ctr++
**
** Find the next available sequence number for cursor P1.
** Write the sequence number into register P2.
** The sequence number on the cursor is incremented after this
** instruction.  
*/
case OP_Sequence: {           /* out2 */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( p->apCsr[pOp->p1]!=0 );
  pOut = out2Prerelease(p, pOp);
  pOut->u.i = p->apCsr[pOp->p1]->seqCount++;
  break;
}


/* Opcode: NewRowid P1 P2 P3 * *
** Synopsis: r[P2]=rowid
................................................................................
** If P3>0 then P3 is a register in the root frame of this VDBE that holds 
** the largest previously generated record number. No new record numbers are
** allowed to be less than this value. When this value reaches its maximum, 
** an SQLITE_FULL error is generated. The P3 register is updated with the '
** generated record number. This P3 mechanism is used to help implement the
** AUTOINCREMENT feature.
*/
case OP_NewRowid: {           /* out2 */
  i64 v;                 /* The new rowid */
  VdbeCursor *pC;        /* Cursor of table to get the new rowid */
  int res;               /* Result of an sqlite3BtreeLast() */
  int cnt;               /* Counter to limit the number of searches */
  Mem *pMem;             /* Register holding largest rowid for AUTOINCREMENT */
  VdbeFrame *pFrame;     /* Root frame of VDBE */

  v = 0;
  res = 0;
  pOut = out2Prerelease(p, pOp);
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  if( NEVER(pC->pCursor==0) ){
    /* The zero initialization above is all that is needed */
  }else{
    /* The next rowid or record number (different terms for the same
................................................................................
** Store in register P2 an integer which is the key of the table entry that
** P1 is currently point to.
**
** P1 can be either an ordinary table or a virtual table.  There used to
** be a separate OP_VRowid opcode for use with virtual tables, but this
** one opcode now works for both table types.
*/
case OP_Rowid: {                 /* out2 */
  VdbeCursor *pC;
  i64 v;
  sqlite3_vtab *pVtab;
  const sqlite3_module *pModule;

  pOut = out2Prerelease(p, pOp);
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->pseudoTableReg==0 || pC->nullRow );
  if( pC->nullRow ){
    pOut->flags = MEM_Null;
    break;
................................................................................
**
** Write into register P2 an integer which is the last entry in the record at
** the end of the index key pointed to by cursor P1.  This integer should be
** the rowid of the table entry to which this index entry points.
**
** See also: Rowid, MakeRecord.
*/
case OP_IdxRowid: {              /* out2 */
  BtCursor *pCrsr;
  VdbeCursor *pC;
  i64 rowid;

  pOut = out2Prerelease(p, pOp);
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  pCrsr = pC->pCursor;
  assert( pCrsr!=0 );
  pOut->flags = MEM_Null;
  assert( pC->isTable==0 );
................................................................................
** is stored in register P2.  If no page 
** movement was required (because the table being dropped was already 
** the last one in the database) then a zero is stored in register P2.
** If AUTOVACUUM is disabled then a zero is stored in register P2.
**
** See also: Clear
*/
case OP_Destroy: {     /* out2 */
  int iMoved;
  int iDb;

  assert( p->readOnly==0 );
  pOut = out2Prerelease(p, pOp);
  pOut->flags = MEM_Null;
  if( db->nVdbeRead > db->nVDestroy+1 ){
    rc = SQLITE_LOCKED;
    p->errorAction = OE_Abort;
  }else{
    iDb = pOp->p3;
    assert( DbMaskTest(p->btreeMask, iDb) );
................................................................................
** Allocate a new index in the main database file if P1==0 or in the
** auxiliary database file if P1==1 or in an attached database if
** P1>1.  Write the root page number of the new table into
** register P2.
**
** See documentation on OP_CreateTable for additional information.
*/
case OP_CreateIndex:            /* out2 */
case OP_CreateTable: {          /* out2 */
  int pgno;
  int flags;
  Db *pDb;

  pOut = out2Prerelease(p, pOp);
  pgno = 0;
  assert( pOp->p1>=0 && pOp->p1<db->nDb );
  assert( DbMaskTest(p->btreeMask, pOp->p1) );
  assert( p->readOnly==0 );
  pDb = &db->aDb[pOp->p1];
  assert( pDb->pBt!=0 );
  if( pOp->opcode==OP_CreateTable ){
................................................................................
** address space. This is used by trigger programs to access the new.* 
** and old.* values.
**
** The address of the cell in the parent frame is determined by adding
** the value of the P1 argument to the value of the P1 argument to the
** calling OP_Program instruction.
*/
case OP_Param: {           /* out2 */
  VdbeFrame *pFrame;
  Mem *pIn;
  pOut = out2Prerelease(p, pOp);
  pFrame = p->pFrame;
  pIn = &pFrame->aMem[pOp->p1 + pFrame->aOp[pFrame->pc].p1];   
  sqlite3VdbeMemShallowCopy(pOut, pIn, MEM_Ephem);
  break;
}

#endif /* #ifndef SQLITE_OMIT_TRIGGER */
................................................................................
** modes (delete, truncate, persist, off and memory), this is a simple
** operation. No IO is required.
**
** If changing into or out of WAL mode the procedure is more complicated.
**
** Write a string containing the final journal-mode to register P2.
*/
case OP_JournalMode: {    /* out2 */
  Btree *pBt;                     /* Btree to change journal mode of */
  Pager *pPager;                  /* Pager associated with pBt */
  int eNew;                       /* New journal mode */
  int eOld;                       /* The old journal mode */
#ifndef SQLITE_OMIT_WAL
  const char *zFilename;          /* Name of database file for pPager */
#endif

  pOut = out2Prerelease(p, pOp);
  eNew = pOp->p3;
  assert( eNew==PAGER_JOURNALMODE_DELETE 
       || eNew==PAGER_JOURNALMODE_TRUNCATE 
       || eNew==PAGER_JOURNALMODE_PERSIST 
       || eNew==PAGER_JOURNALMODE_OFF
       || eNew==PAGER_JOURNALMODE_MEMORY
       || eNew==PAGER_JOURNALMODE_WAL
................................................................................
#endif /* SQLITE_OMIT_VIRTUALTABLE */

#ifndef  SQLITE_OMIT_PAGER_PRAGMAS
/* Opcode: Pagecount P1 P2 * * *
**
** Write the current number of pages in database P1 to memory cell P2.
*/
case OP_Pagecount: {            /* out2 */
  pOut = out2Prerelease(p, pOp);
  pOut->u.i = sqlite3BtreeLastPage(db->aDb[pOp->p1].pBt);
  break;
}
#endif


#ifndef  SQLITE_OMIT_PAGER_PRAGMAS
................................................................................
**
** Try to set the maximum page count for database P1 to the value in P3.
** Do not let the maximum page count fall below the current page count and
** do not change the maximum page count value if P3==0.
**
** Store the maximum page count after the change in register P2.
*/
case OP_MaxPgcnt: {            /* out2 */
  unsigned int newMax;
  Btree *pBt;

  pOut = out2Prerelease(p, pOp);
  pBt = db->aDb[pOp->p1].pBt;
  newMax = 0;
  if( pOp->p3 ){
    newMax = sqlite3BtreeLastPage(pBt);
    if( newMax < (unsigned)pOp->p3 ) newMax = (unsigned)pOp->p3;
  }
  pOut->u.i = sqlite3BtreeMaxPageCount(pBt, newMax);
................................................................................
    */
#ifndef NDEBUG
    assert( pc>=-1 && pc<p->nOp );

#ifdef SQLITE_DEBUG
    if( db->flags & SQLITE_VdbeTrace ){
      if( rc!=0 ) printf("rc=%d\n",rc);
      if( pOp->opflags & (OPFLG_OUT2) ){
        registerTrace(pOp->p2, &aMem[pOp->p2]);
      }
      if( pOp->opflags & OPFLG_OUT3 ){
        registerTrace(pOp->p3, &aMem[pOp->p3]);
      }
    }
#endif  /* SQLITE_DEBUG */