SQLite

  order[n_op++] = "OP_Explain";

  # Assign small values to opcodes that are processed by resolveP2Values()
  # to make code generation for the switch() statement smaller and faster.
  for(i=0; i<n_op; i++){
    name = order[i];
    if( op[name]>=0 ) continue;


    if( name=="OP_Transaction"   \
     || name=="OP_AutoCommit"    \
     || name=="OP_Savepoint"     \
     || name=="OP_Checkpoint"    \
     || name=="OP_Vacuum"        \
     || name=="OP_JournalMode"   \
     || name=="OP_VUpdate"       \
     || name=="OP_VFilter"       \

#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  sqlite3VdbeAddOp2(v, OP_Integer, iParam, regStat4+1);
#elif SQLITE_DEBUG
  assert( iParam==STAT_GET_STAT1 );
#else
  UNUSED_PARAMETER( iParam );
#endif
  sqlite3VdbeAddOp3(v, OP_Function0, 0, regStat4, regOut);
  sqlite3VdbeChangeP4(v, -1, (char*)&statGetFuncdef, P4_FUNCDEF);
  sqlite3VdbeChangeP5(v, 1 + IsStat34);
}

/*
** Generate code to do an analysis of all indices associated with
** a single table.

    ** The third argument is only used for STAT3 and STAT4
    */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
    sqlite3VdbeAddOp2(v, OP_Count, iIdxCur, regStat4+3);
#endif
    sqlite3VdbeAddOp2(v, OP_Integer, nCol, regStat4+1);
    sqlite3VdbeAddOp2(v, OP_Integer, pIdx->nKeyCol, regStat4+2);
    sqlite3VdbeAddOp3(v, OP_Function0, 0, regStat4+1, regStat4);
    sqlite3VdbeChangeP4(v, -1, (char*)&statInitFuncdef, P4_FUNCDEF);
    sqlite3VdbeChangeP5(v, 2+IsStat34);

    /* Implementation of the following:
    **
    **   Rewind csr
    **   if eof(csr) goto end_of_scan;

        VdbeComment((v, "%s", pTab->aCol[pPk->aiColumn[j]].zName));
      }
      sqlite3VdbeAddOp3(v, OP_MakeRecord, regKey, pPk->nKeyCol, regRowid);
      sqlite3ReleaseTempRange(pParse, regKey, pPk->nKeyCol);
    }
#endif
    assert( regChng==(regStat4+1) );
    sqlite3VdbeAddOp3(v, OP_Function0, 1, regStat4, regTemp);
    sqlite3VdbeChangeP4(v, -1, (char*)&statPushFuncdef, P4_FUNCDEF);
    sqlite3VdbeChangeP5(v, 2+IsStat34);
    sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);

    /* Add the entry to the stat1 table. */
    callStatGet(v, regStat4, STAT_GET_STAT1, regStat1);
    assert( "BBB"[0]==SQLITE_AFF_TEXT );

  regArgs = sqlite3GetTempRange(pParse, 4);
  sqlite3ExprCode(pParse, pFilename, regArgs);
  sqlite3ExprCode(pParse, pDbname, regArgs+1);
  sqlite3ExprCode(pParse, pKey, regArgs+2);

  assert( v || db->mallocFailed );
  if( v ){
    sqlite3VdbeAddOp3(v, OP_Function0, 0, regArgs+3-pFunc->nArg, regArgs+3);
    assert( pFunc->nArg==-1 || (pFunc->nArg&0xff)==pFunc->nArg );
    sqlite3VdbeChangeP5(v, (u8)(pFunc->nArg));
    sqlite3VdbeChangeP4(v, -1, (char *)pFunc, P4_FUNCDEF);

    /* Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this
    ** statement only). For DETACH, set it to false (expire all existing
    ** statements).

        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[0].pExpr);
      }
#endif
      if( pDef->funcFlags & SQLITE_FUNC_NEEDCOLL ){
        if( !pColl ) pColl = db->pDfltColl; 
        sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
      }
      sqlite3VdbeAddOp4(v, OP_Function0, constMask, r1, target,
                        (char*)pDef, P4_FUNCDEF);
      sqlite3VdbeChangeP5(v, (u8)nFarg);
      if( nFarg && constMask==0 ){
        sqlite3ReleaseTempRange(pParse, r1, nFarg);
      }
      break;
    }

      }
      if( !pColl ){
        pColl = pParse->db->pDfltColl;
      }
      if( regHit==0 && pAggInfo->nAccumulator ) regHit = ++pParse->nMem;
      sqlite3VdbeAddOp4(v, OP_CollSeq, regHit, 0, 0, (char *)pColl, P4_COLLSEQ);
    }
    sqlite3VdbeAddOp4(v, OP_AggStep0, 0, regAgg, pF->iMem,
                      (void*)pF->pFunc, P4_FUNCDEF);
    sqlite3VdbeChangeP5(v, (u8)nArg);
    sqlite3ExprCacheAffinityChange(pParse, regAgg, nArg);
    sqlite3ReleaseTempRange(pParse, regAgg, nArg);
    if( addrNext ){
      sqlite3VdbeResolveLabel(v, addrNext);
      sqlite3ExprCacheClear(pParse);

  assert( pOp->p4type==P4_COLLSEQ );
  if( pOp->p1 ){
    sqlite3VdbeMemSetInt64(&aMem[pOp->p1], 0);
  }
  break;
}

/* Opcode: Function0 P1 P2 P3 P4 P5
** Synopsis: r[P3]=func(r[P2@P5])
**
** Invoke a user function (P4 is a pointer to a Function structure that
** defines the function) with P5 arguments taken from register P2 and
** successors.  The result of the function is stored in register P3.
** Register P3 must not be one of the function inputs.
**
** P1 is a 32-bit bitmask indicating whether or not each argument to the 
** function was determined to be constant at compile time. If the first
** argument was constant then bit 0 of P1 is set. This is used to determine
** whether meta data associated with a user function argument using the
** sqlite3_set_auxdata() API may be safely retained until the next
** invocation of this opcode.
**
** See also: Function, AggStep, AggFinal
*/
/* Opcode: Function P1 P2 P3 P4 P5
** Synopsis: r[P3]=func(r[P2@P5])
**
** Invoke a user function (P4 is a pointer to an sqlite3_context object that
** contains a pointer to the function to be run) with P5 arguments taken
** from register P2 and successors.  The result of the function is stored
** in register P3.  Register P3 must not be one of the function inputs.
**
** P1 is a 32-bit bitmask indicating whether or not each argument to the 
** function was determined to be constant at compile time. If the first
** argument was constant then bit 0 of P1 is set. This is used to determine
** whether meta data associated with a user function argument using the
** sqlite3_set_auxdata() API may be safely retained until the next
** invocation of this opcode.
**
** SQL functions are initially coded as OP_Function0 with P4 pointing
** to the function itself.  But on first evaluation, the P4 operand is
** automatically converted into an sqlite3_context object and the operation
** changed to this OP_Function opcode.  In this way, the initialization of
** the sqlite3_context object occurs only once, rather than once for each
** evaluation of the function.
**
** See also: Function0, AggStep, AggFinal
*/
case OP_Function0: {
  int n;
  sqlite3_context *pCtx;

















  assert( pOp->p4type==P4_FUNCDEF );
  n = pOp->p5;
  assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
  assert( n==0 || (pOp->p2>0 && pOp->p2+n<=(p->nMem-p->nCursor)+1) );
  assert( pOp->p3<pOp->p2 || pOp->p3>=pOp->p2+n );
  pCtx = sqlite3DbMallocRaw(db, sizeof(*pCtx) + (n-1)*sizeof(sqlite3_value*));
  if( pCtx==0 ) goto no_mem;
  pCtx->pOut = 0;
  pCtx->pFunc = pOp->p4.pFunc;
  pCtx->iOp = (int)(pOp - aOp);
  pCtx->pVdbe = p;
  pCtx->argc = n;
  pOp->p4type = P4_FUNCCTX;
  pOp->p4.pCtx = pCtx;
  pOp->opcode = OP_Function;
  /* Fall through into OP_Function */
}
case OP_Function: {
  int i;
  sqlite3_context *pCtx;

  assert( pOp->p4type==P4_FUNCCTX );
  pCtx = pOp->p4.pCtx;

  /* If this function is inside of a trigger, the register array in aMem[]
  ** might change from one evaluation to the next.  The next block of code
  ** checks to see if the register array has changed, and if so it
  ** reinitializes the relavant parts of the sqlite3_context object */
  if( pCtx->pOut != &aMem[pOp->p3] ){
    pCtx->pOut = &aMem[pOp->p3];
    for(i=pCtx->argc-1; i>=0; i--) pCtx->argv[i] = &aMem[pOp->p2+i];
  }

  memAboutToChange(p, pCtx->pOut);
#ifdef SQLITE_DEBUG
  for(i=0; i<pCtx->argc; i++){
    assert( memIsValid(pCtx->argv[i]) );
    REGISTER_TRACE(pOp->p2+i, pCtx->argv[i]);
  }
#endif
  MemSetTypeFlag(pCtx->pOut, MEM_Null);
  pCtx->fErrorOrAux = 0;
  db->lastRowid = lastRowid;
  (*pCtx->pFunc->xFunc)(pCtx, pCtx->argc, pCtx->argv); /* IMP: R-24505-23230 */
  lastRowid = db->lastRowid;  /* Remember rowid changes made by xFunc */

  /* If the function returned an error, throw an exception */
  if( pCtx->fErrorOrAux ){
    if( pCtx->isError ){
      sqlite3VdbeError(p, "%s", sqlite3_value_text(pCtx->pOut));
      rc = pCtx->isError;
    }
    sqlite3VdbeDeleteAuxData(p, (int)(pOp - aOp), pOp->p1);
  }

  /* Copy the result of the function into register P3 */
  sqlite3VdbeChangeEncoding(pCtx->pOut, encoding);
  if( sqlite3VdbeMemTooBig(pCtx->pOut) ){
    goto too_big;
  }

  REGISTER_TRACE(pOp->p3, pCtx->pOut);
  UPDATE_MAX_BLOBSIZE(pCtx->pOut);
  break;
}

/* Opcode: BitAnd P1 P2 P3 * *
** Synopsis:  r[P3]=r[P1]&r[P2]
**
** Take the bit-wise AND of the values in register P1 and P2 and

** function has P5 arguments.   P4 is a pointer to the FuncDef
** structure that specifies the function.  Use register
** P3 as the accumulator.
**
** The P5 arguments are taken from register P2 and its
** successors.
*/
case OP_AggStep0: {
  int n;
  sqlite3_context *pCtx;

  assert( pOp->p4type==P4_FUNCDEF );
  n = pOp->p5;
  assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
  assert( n==0 || (pOp->p2>0 && pOp->p2+n<=(p->nMem-p->nCursor)+1) );
  assert( pOp->p3<pOp->p2 || pOp->p3>=pOp->p2+n );
  pCtx = sqlite3DbMallocRaw(db, sizeof(*pCtx) + (n-1)*sizeof(sqlite3_value*));
  if( pCtx==0 ) goto no_mem;
  pCtx->pMem = 0;
  pCtx->pFunc = pOp->p4.pFunc;
  pCtx->iOp = (int)(pOp - aOp);
  pCtx->pVdbe = p;
  pCtx->argc = n;
  pOp->p4type = P4_FUNCCTX;
  pOp->p4.pCtx = pCtx;
  pOp->opcode = OP_AggStep;
  /* Fall through into OP_AggStep */
}
case OP_AggStep: {
  int i;
  sqlite3_context *pCtx;
  Mem *pMem;

  Mem t;



  assert( pOp->p4type==P4_FUNCCTX );
  pCtx = pOp->p4.pCtx;

  pMem = &aMem[pOp->p3];

  /* If this function is inside of a trigger, the register array in aMem[]
  ** might change from one evaluation to the next.  The next block of code
  ** checks to see if the register array has changed, and if so it
  ** reinitializes the relavant parts of the sqlite3_context object */
  if( pCtx->pMem != pMem ){
    pCtx->pMem = pMem;
    for(i=pCtx->argc-1; i>=0; i--) pCtx->argv[i] = &aMem[pOp->p2+i];
  }

#ifdef SQLITE_DEBUG
  for(i=0; i<pCtx->argc; i++){
    assert( memIsValid(pCtx->argv[i]) );
    REGISTER_TRACE(pOp->p2+i, pCtx->argv[i]);

  }
#endif



  pMem->n++;
  sqlite3VdbeMemInit(&t, db, MEM_Null);
  pCtx->pOut = &t;
  pCtx->fErrorOrAux = 0;


  pCtx->skipFlag = 0;
  (pCtx->pFunc->xStep)(pCtx,pCtx->argc,pCtx->argv); /* IMP: R-24505-23230 */
  if( pCtx->fErrorOrAux ){
    if( pCtx->isError ){
      sqlite3VdbeError(p, "%s", sqlite3_value_text(&t));
      rc = pCtx->isError;
    }
    sqlite3VdbeMemRelease(&t);
  }else{
    assert( t.flags==MEM_Null );
  }
  if( pCtx->skipFlag ){
    assert( pOp[-1].opcode==OP_CollSeq );
    i = pOp[-1].p1;
    if( i ) sqlite3VdbeMemSetInt64(&aMem[i], 1);
  }

  break;
}

/* Opcode: AggFinal P1 P2 * P4 *
** Synopsis: accum=r[P1] N=P2
**
** Execute the finalizer function for an aggregate.  P1 is

  u8 opcode;          /* What operation to perform */
  signed char p4type; /* One of the P4_xxx constants for p4 */
  u8 opflags;         /* Mask of the OPFLG_* flags in opcodes.h */
  u8 p5;              /* Fifth parameter is an unsigned character */
  int p1;             /* First operand */
  int p2;             /* Second parameter (often the jump destination) */
  int p3;             /* The third parameter */
  union p4union {     /* fourth parameter */
    int i;                 /* Integer value if p4type==P4_INT32 */
    void *p;               /* Generic pointer */
    char *z;               /* Pointer to data for string (char array) types */
    i64 *pI64;             /* Used when p4type is P4_INT64 */
    double *pReal;         /* Used when p4type is P4_REAL */
    FuncDef *pFunc;        /* Used when p4type is P4_FUNCDEF */
    sqlite3_context *pCtx; /* Used when p4type is P4_FUNCCTX */
    CollSeq *pColl;        /* Used when p4type is P4_COLLSEQ */
    Mem *pMem;             /* Used when p4type is P4_MEM */
    VTable *pVtab;         /* Used when p4type is P4_VTAB */
    KeyInfo *pKeyInfo;     /* Used when p4type is P4_KEYINFO */
    int *ai;               /* Used when p4type is P4_INTARRAY */
    SubProgram *pProgram;  /* Used when p4type is P4_SUBPROGRAM */
    int (*xAdvance)(BtCursor *, int *);

#define P4_MPRINTF  (-11) /* P4 is a string obtained from sqlite3_mprintf() */
#define P4_REAL     (-12) /* P4 is a 64-bit floating point value */
#define P4_INT64    (-13) /* P4 is a 64-bit signed integer */
#define P4_INT32    (-14) /* P4 is a 32-bit signed integer */
#define P4_INTARRAY (-15) /* P4 is a vector of 32-bit integers */
#define P4_SUBPROGRAM  (-18) /* P4 is a pointer to a SubProgram structure */
#define P4_ADVANCE  (-19) /* P4 is a pointer to BtreeNext() or BtreePrev() */
#define P4_FUNCCTX  (-20) /* P4 is a pointer to an sqlite3_context object */

/* Error message codes for OP_Halt */
#define P5_ConstraintNotNull 1
#define P5_ConstraintUnique  2
#define P5_ConstraintCheck   3
#define P5_ConstraintFK      4

** But this file is the only place where the internal details of this
** structure are known.
**
** This structure is defined inside of vdbeInt.h because it uses substructures
** (Mem) which are only defined there.
*/
struct sqlite3_context {
  Mem *pOut;              /* The return value is stored here */
  FuncDef *pFunc;         /* Pointer to function information */
  Mem *pMem;              /* Memory cell used to store aggregate context */
  Vdbe *pVdbe;            /* The VM that owns this context */
  int iOp;                /* Instruction number of OP_Function */
  int isError;            /* Error code returned by the function. */
  u8 skipFlag;            /* Skip accumulator loading if true */
  u8 fErrorOrAux;         /* isError!=0 or pVdbe->pAuxData modified */
  u8 argc;                /* Number of arguments */
  sqlite3_value *argv[1]; /* Argument set */
};

/*
** An Explain object accumulates indented output which is helpful
** in describing recursive data structures.
*/
struct Explain {

  p->bIsReader = 0;
  for(pOp=p->aOp, i=p->nOp-1; i>=0; i--, pOp++){
    u8 opcode = pOp->opcode;

    /* NOTE: Be sure to update mkopcodeh.awk when adding or removing
    ** cases from this switch! */
    switch( opcode ){





      case OP_Transaction: {
        if( pOp->p2!=0 ) p->readOnly = 0;
        /* fall thru */
      }
      case OP_AutoCommit:
      case OP_Savepoint: {
        p->bIsReader = 1;

/*
** Delete a P4 value if necessary.
*/
static void freeP4(sqlite3 *db, int p4type, void *p4){
  if( p4 ){
    assert( db );
    switch( p4type ){
      case P4_FUNCCTX: {
        freeEphemeralFunction(db, ((sqlite3_context*)p4)->pFunc);
        /* Fall through into the next case */
      }
      case P4_REAL:
      case P4_INT64:
      case P4_DYNAMIC:
      case P4_INTARRAY: {
        sqlite3DbFree(db, p4);
        break;
      }

      sqlite3_snprintf(nTemp, zTemp, "(%.20s)", pColl->zName);
      break;
    }
    case P4_FUNCDEF: {
      FuncDef *pDef = pOp->p4.pFunc;
      sqlite3_snprintf(nTemp, zTemp, "%s(%d)", pDef->zName, pDef->nArg);
      break;
    }
    case P4_FUNCCTX: {
      FuncDef *pDef = pOp->p4.pCtx->pFunc;
      sqlite3_snprintf(nTemp, zTemp, "%s(%d)", pDef->zName, pDef->nArg);
      break;
    }
    case P4_INT64: {
      sqlite3_snprintf(nTemp, zTemp, "%lld", *pOp->p4.pI64);
      break;
    }
    case P4_INT32: {
      sqlite3_snprintf(nTemp, zTemp, "%d", pOp->p4.i);