SQLite

){
  va_list ap;
  if( !pCheck->mxErr ) return;
  pCheck->mxErr--;
  pCheck->nErr++;
  va_start(ap, zFormat);
  if( pCheck->errMsg.nChar ){
    sqlite3_str_append(&pCheck->errMsg, "\n", 1);
  }
  if( pCheck->zPfx ){
    sqlite3_str_appendf(&pCheck->errMsg, pCheck->zPfx, pCheck->v1, pCheck->v2);
  }
  sqlite3_str_vappendf(&pCheck->errMsg, zFormat, ap);
  va_end(ap);
  if( pCheck->errMsg.accError==SQLITE_NOMEM ){
    pCheck->mallocFailed = 1;
  }
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

#ifndef SQLITE_OMIT_INTEGRITY_CHECK

  /* Clean  up and report errors.
  */
integrity_ck_cleanup:
  sqlite3PageFree(sCheck.heap);
  sqlite3_free(sCheck.aPgRef);
  if( sCheck.mallocFailed ){
    sqlite3_str_reset(&sCheck.errMsg);
    sCheck.nErr++;
  }
  *pnErr = sCheck.nErr;
  if( sCheck.nErr==0 ) sqlite3_str_reset(&sCheck.errMsg);
  /* Make sure this analysis did not leave any unref() pages. */
  assert( nRef==sqlite3PagerRefcount(pBt->pPager) );
  sqlite3BtreeLeave(p);
  return sqlite3StrAccumFinish(&sCheck.errMsg);
}
#endif /* SQLITE_OMIT_INTEGRITY_CHECK */

  char *zErr;
  int j;
  StrAccum errMsg;
  Table *pTab = pIdx->pTable;

  sqlite3StrAccumInit(&errMsg, pParse->db, 0, 0, 200);
  if( pIdx->aColExpr ){
    sqlite3_str_appendf(&errMsg, "index '%q'", pIdx->zName);
  }else{
    for(j=0; j<pIdx->nKeyCol; j++){
      char *zCol;
      assert( pIdx->aiColumn[j]>=0 );
      zCol = pTab->aCol[pIdx->aiColumn[j]].zName;
      if( j ) sqlite3_str_append(&errMsg, ", ", 2);
      sqlite3_str_appendall(&errMsg, pTab->zName);
      sqlite3_str_append(&errMsg, ".", 1);
      sqlite3_str_appendall(&errMsg, zCol);
    }
  }
  zErr = sqlite3StrAccumFinish(&errMsg);
  sqlite3HaltConstraint(pParse, 
    IsPrimaryKeyIndex(pIdx) ? SQLITE_CONSTRAINT_PRIMARYKEY 
                            : SQLITE_CONSTRAINT_UNIQUE,
    onError, zErr, P4_DYNAMIC, P5_ConstraintUnique);

  if( argc>=1 && (zFormat = (const char*)sqlite3_value_text(argv[0]))!=0 ){
    x.nArg = argc-1;
    x.nUsed = 0;
    x.apArg = argv+1;
    sqlite3StrAccumInit(&str, db, 0, 0, db->aLimit[SQLITE_LIMIT_LENGTH]);
    str.printfFlags = SQLITE_PRINTF_SQLFUNC;
    sqlite3_str_appendf(&str, zFormat, &x);
    n = str.nChar;
    sqlite3_result_text(context, sqlite3StrAccumFinish(&str), n,
                        SQLITE_DYNAMIC);
  }
}

/*

      if( argc==2 ){
        zSep = (char*)sqlite3_value_text(argv[1]);
        nSep = sqlite3_value_bytes(argv[1]);
      }else{
        zSep = ",";
        nSep = 1;
      }
      if( zSep ) sqlite3_str_append(pAccum, zSep, nSep);
    }
    zVal = (char*)sqlite3_value_text(argv[0]);
    nVal = sqlite3_value_bytes(argv[0]);
    if( zVal ) sqlite3_str_append(pAccum, zVal, nVal);
  }
}
static void groupConcatFinalize(sqlite3_context *context){
  StrAccum *pAccum;
  pAccum = sqlite3_aggregate_context(context, 0);
  if( pAccum ){
    if( pAccum->accError==SQLITE_TOOBIG ){
      sqlite3_result_error_toobig(context);
    }else if( pAccum->accError==SQLITE_NOMEM ){
      sqlite3_result_error_nomem(context);
    }else{    
      sqlite3_result_text(context, sqlite3StrAccumFinish(pAccum), -1, 
                          sqlite3_free);
    }
  }
}

int sqlite3_mutex_notheld(sqlite3_mutex *p){
  assert( p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld );
  return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p);
}
#endif

#endif /* !defined(SQLITE_MUTEX_OMIT) */

  char cSep = '(';
  StrAccum acc;
  char zBuf[200];

  UNUSED_PARAMETER(argc);
  UNUSED_PARAMETER(argv);
  sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
  sqlite3_str_appendall(&acc, "CREATE TABLE x");
  for(i=0, j=pPragma->iPragCName; i<pPragma->nPragCName; i++, j++){
    sqlite3_str_appendf(&acc, "%c\"%s\"", cSep, pragCName[j]);
    cSep = ',';
  }
  if( i==0 ){
    sqlite3_str_appendf(&acc, "(\"%s\"", pPragma->zName);
    cSep = ',';
    i++;
  }
  j = 0;
  if( pPragma->mPragFlg & PragFlg_Result1 ){
    sqlite3_str_appendall(&acc, ",arg HIDDEN");
    j++;
  }
  if( pPragma->mPragFlg & (PragFlg_SchemaOpt|PragFlg_SchemaReq) ){
    sqlite3_str_appendall(&acc, ",schema HIDDEN");
    j++;
  }
  sqlite3_str_append(&acc, ")", 1);
  sqlite3StrAccumFinish(&acc);
  assert( strlen(zBuf) < sizeof(zBuf)-1 );
  rc = sqlite3_declare_vtab(db, zBuf);
  if( rc==SQLITE_OK ){
    pTab = (PragmaVtab*)sqlite3_malloc(sizeof(PragmaVtab));
    if( pTab==0 ){
      rc = SQLITE_NOMEM;

      pCsr->azArg[j] = sqlite3_mprintf("%s", zText);
      if( pCsr->azArg[j]==0 ){
        return SQLITE_NOMEM;
      }
    }
  }
  sqlite3StrAccumInit(&acc, 0, 0, 0, pTab->db->aLimit[SQLITE_LIMIT_SQL_LENGTH]);
  sqlite3_str_appendall(&acc, "PRAGMA ");
  if( pCsr->azArg[1] ){
    sqlite3_str_appendf(&acc, "%Q.", pCsr->azArg[1]);
  }
  sqlite3_str_appendall(&acc, pTab->pName->zName);
  if( pCsr->azArg[0] ){
    sqlite3_str_appendf(&acc, "=%Q", pCsr->azArg[0]);
  }
  zSql = sqlite3StrAccumFinish(&acc);
  if( zSql==0 ) return SQLITE_NOMEM;
  rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pPragma, 0);
  sqlite3_free(zSql);
  if( rc!=SQLITE_OK ){
    pTab->base.zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(pTab->db));

}
#endif /* SQLITE_OMIT_FLOATING_POINT */

/*
** Set the StrAccum object to an error mode.
*/
static void setStrAccumError(StrAccum *p, u8 eError){
  assert( eError==SQLITE_NOMEM || eError==SQLITE_TOOBIG );
  p->accError = eError;
  p->nAlloc = 0;
}

/*
** Extra argument values from a PrintfArguments object
*/

# define SQLITE_PRINT_BUF_SIZE 70
#endif
#define etBUFSIZE SQLITE_PRINT_BUF_SIZE  /* Size of the output buffer */

/*
** Render a string given by "fmt" into the StrAccum object.
*/
void sqlite3_str_vappendf(
  sqlite3_str *pAccum,       /* Accumulate results here */
  const char *fmt,           /* Format string */
  va_list ap                 /* arguments */
){
  int c;                     /* Next character in the format string */
  char *bufpt;               /* Pointer to the conversion buffer */
  int precision;             /* Precision of the current field */
  int length;                /* Length of the field */

    if( c!='%' ){
      bufpt = (char *)fmt;
#if HAVE_STRCHRNUL
      fmt = strchrnul(fmt, '%');
#else
      do{ fmt++; }while( *fmt && *fmt != '%' );
#endif
      sqlite3_str_append(pAccum, bufpt, (int)(fmt - bufpt));
      if( *fmt==0 ) break;
    }
    if( (c=(*++fmt))==0 ){
      sqlite3_str_append(pAccum, "%", 1);
      break;
    }
    /* Find out what flags are present */
    flag_leftjustify = flag_prefix = cThousand =
     flag_alternateform = flag_altform2 = flag_zeropad = 0;
    done = 0;
    do{

        if( precision<etBUFSIZE-10-etBUFSIZE/3 ){
          nOut = etBUFSIZE;
          zOut = buf;
        }else{
          u64 n = (u64)precision + 10 + precision/3;
          zOut = zExtra = sqlite3Malloc( n );
          if( zOut==0 ){
            setStrAccumError(pAccum, SQLITE_NOMEM);
            return;
          }
          nOut = (int)n;
        }
        bufpt = &zOut[nOut-1];
        if( xtype==etORDINAL ){
          static const char zOrd[] = "thstndrd";

        }else{
          e2 = exp;
        }
        if( MAX(e2,0)+(i64)precision+(i64)width > etBUFSIZE - 15 ){
          bufpt = zExtra 
              = sqlite3Malloc( MAX(e2,0)+(i64)precision+(i64)width+15 );
          if( bufpt==0 ){
            setStrAccumError(pAccum, SQLITE_NOMEM);
            return;
          }
        }
        zOut = bufpt;
        nsd = 16 + flag_altform2*10;
        flag_dp = (precision>0 ?1:0) | flag_alternateform | flag_altform2;
        /* The sign in front of the number */

            buf[3] = 0x80 + (u8)(ch & 0x3f);
            length = 4;
          }
        }
        if( precision>1 ){
          width -= precision-1;
          if( width>1 && !flag_leftjustify ){
            sqlite3_str_appendchar(pAccum, width-1, ' ');
            width = 0;
          }
          while( precision-- > 1 ){
            sqlite3_str_append(pAccum, buf, length);
          }
        }
        bufpt = buf;
        flag_altform2 = 1;
        goto adjust_width_for_utf8;
      case etSTRING:
      case etDYNSTRING:

          }
        }
        needQuote = !isnull && xtype==etSQLESCAPE2;
        n += i + 3;
        if( n>etBUFSIZE ){
          bufpt = zExtra = sqlite3Malloc( n );
          if( bufpt==0 ){
            setStrAccumError(pAccum, SQLITE_NOMEM);
            return;
          }
        }else{
          bufpt = buf;
        }
        j = 0;
        if( needQuote ) bufpt[j++] = q;

      }
      case etTOKEN: {
        Token *pToken;
        if( (pAccum->printfFlags & SQLITE_PRINTF_INTERNAL)==0 ) return;
        pToken = va_arg(ap, Token*);
        assert( bArgList==0 );
        if( pToken && pToken->n ){
          sqlite3_str_append(pAccum, (const char*)pToken->z, pToken->n);
        }
        length = width = 0;
        break;
      }
      case etSRCLIST: {
        SrcList *pSrc;
        int k;
        struct SrcList_item *pItem;
        if( (pAccum->printfFlags & SQLITE_PRINTF_INTERNAL)==0 ) return;
        pSrc = va_arg(ap, SrcList*);
        k = va_arg(ap, int);
        pItem = &pSrc->a[k];
        assert( bArgList==0 );
        assert( k>=0 && k<pSrc->nSrc );
        if( pItem->zDatabase ){
          sqlite3_str_appendall(pAccum, pItem->zDatabase);
          sqlite3_str_append(pAccum, ".", 1);
        }
        sqlite3_str_appendall(pAccum, pItem->zName);
        length = width = 0;
        break;
      }
      default: {
        assert( xtype==etINVALID );
        return;
      }
    }/* End switch over the format type */
    /*
    ** The text of the conversion is pointed to by "bufpt" and is
    ** "length" characters long.  The field width is "width".  Do
    ** the output.  Both length and width are in bytes, not characters,
    ** at this point.  If the "!" flag was present on string conversions
    ** indicating that width and precision should be expressed in characters,
    ** then the values have been translated prior to reaching this point.
    */
    width -= length;
    if( width>0 ){
      if( !flag_leftjustify ) sqlite3_str_appendchar(pAccum, width, ' ');
      sqlite3_str_append(pAccum, bufpt, length);
      if( flag_leftjustify ) sqlite3_str_appendchar(pAccum, width, ' ');
    }else{
      sqlite3_str_append(pAccum, bufpt, length);
    }

    if( zExtra ){
      sqlite3DbFree(pAccum->db, zExtra);
      zExtra = 0;
    }
  }/* End for loop over the format string */
} /* End of function */

/*
** Enlarge the memory allocation on a StrAccum object so that it is
** able to accept at least N more bytes of text.
**
** Return the number of bytes of text that StrAccum is able to accept
** after the attempted enlargement.  The value returned might be zero.
*/
static int sqlite3StrAccumEnlarge(StrAccum *p, int N){
  char *zNew;
  assert( p->nChar+(i64)N >= p->nAlloc ); /* Only called if really needed */
  if( p->accError ){
    testcase(p->accError==SQLITE_TOOBIG);
    testcase(p->accError==SQLITE_NOMEM);
    return 0;
  }
  if( p->mxAlloc==0 ){
    N = p->nAlloc - p->nChar - 1;
    setStrAccumError(p, SQLITE_TOOBIG);
    return N;
  }else{
    char *zOld = isMalloced(p) ? p->zText : 0;
    i64 szNew = p->nChar;
    szNew += N + 1;
    if( szNew+p->nChar<=p->mxAlloc ){
      /* Force exponential buffer size growth as long as it does not overflow,
      ** to avoid having to call this routine too often */
      szNew += p->nChar;
    }
    if( szNew > p->mxAlloc ){
      sqlite3_str_reset(p);
      setStrAccumError(p, SQLITE_TOOBIG);
      return 0;
    }else{
      p->nAlloc = (int)szNew;
    }
    if( p->db ){
      zNew = sqlite3DbRealloc(p->db, zOld, p->nAlloc);
    }else{
      zNew = sqlite3_realloc64(zOld, p->nAlloc);
    }
    if( zNew ){
      assert( p->zText!=0 || p->nChar==0 );
      if( !isMalloced(p) && p->nChar>0 ) memcpy(zNew, p->zText, p->nChar);
      p->zText = zNew;
      p->nAlloc = sqlite3DbMallocSize(p->db, zNew);
      p->printfFlags |= SQLITE_PRINTF_MALLOCED;
    }else{
      sqlite3_str_reset(p);
      setStrAccumError(p, SQLITE_NOMEM);
      return 0;
    }
  }
  return N;
}

/*
** Append N copies of character c to the given string buffer.
*/
void sqlite3_str_appendchar(sqlite3_str *p, int N, char c){
  testcase( p->nChar + (i64)N > 0x7fffffff );
  if( p->nChar+(i64)N >= p->nAlloc && (N = sqlite3StrAccumEnlarge(p, N))<=0 ){
    return;
  }
  while( (N--)>0 ) p->zText[p->nChar++] = c;
}

/*
** The StrAccum "p" is not large enough to accept N new bytes of z[].
** So enlarge if first, then do the append.
**
** This is a helper routine to sqlite3_str_append() that does special-case
** work (enlarging the buffer) using tail recursion, so that the
** sqlite3_str_append() routine can use fast calling semantics.
*/
static void SQLITE_NOINLINE enlargeAndAppend(StrAccum *p, const char *z, int N){
  N = sqlite3StrAccumEnlarge(p, N);
  if( N>0 ){
    memcpy(&p->zText[p->nChar], z, N);
    p->nChar += N;
  }
}

/*
** Append N bytes of text from z to the StrAccum object.  Increase the
** size of the memory allocation for StrAccum if necessary.
*/
void sqlite3_str_append(sqlite3_str *p, const char *z, int N){
  assert( z!=0 || N==0 );
  assert( p->zText!=0 || p->nChar==0 || p->accError );
  assert( N>=0 );
  assert( p->accError==0 || p->nAlloc==0 );
  if( p->nChar+N >= p->nAlloc ){
    enlargeAndAppend(p,z,N);
  }else if( N ){
    assert( p->zText );
    p->nChar += N;
    memcpy(&p->zText[p->nChar-N], z, N);
  }
}

/*
** Append the complete text of zero-terminated string z[] to the p string.
*/
void sqlite3_str_appendall(sqlite3_str *p, const char *z){
  sqlite3_str_append(p, z, sqlite3Strlen30(z));
}


/*
** Finish off a string by making sure it is zero-terminated.
** Return a pointer to the resulting string.  Return a NULL
** pointer if any kind of error was encountered.
*/
static SQLITE_NOINLINE char *strAccumFinishRealloc(StrAccum *p){
  char *zText;
  assert( p->mxAlloc>0 && !isMalloced(p) );
  zText = sqlite3DbMallocRaw(p->db, p->nChar+1 );
  if( zText ){
    memcpy(zText, p->zText, p->nChar+1);
    p->printfFlags |= SQLITE_PRINTF_MALLOCED;
  }else{
    setStrAccumError(p, SQLITE_NOMEM);
  }
  p->zText = zText;
  return zText;
}
char *sqlite3StrAccumFinish(StrAccum *p){
  if( p->zText ){
    p->zText[p->nChar] = 0;
    if( p->mxAlloc>0 && !isMalloced(p) ){
      return strAccumFinishRealloc(p);
    }
  }
  return p->zText;
}

/* Finalize a string created using sqlite3_str_new().
*/
char *sqlite3_str_finish(sqlite3_str *p){
  char *z;
  if( p ){
    z = sqlite3StrAccumFinish(p);
    sqlite3DbFree(p->db, p);
  }else{
    z = 0;
  }
  return z;
}

/* Return any error code associated with p */
int sqlite3_str_errcode(sqlite3_str *p){
  return p ? p->accError : SQLITE_NOMEM;
}

/* Return the current length of p in bytes */
int sqlite3_str_length(sqlite3_str *p){
  return p ? p->nChar : 0;
}

/* Return the current value for p */
char *sqlite3_str_value(sqlite3_str *p){
  return p ? p->zText : 0;
}

/*
** Reset an StrAccum string.  Reclaim all malloced memory.
*/
void sqlite3_str_reset(StrAccum *p){
  if( isMalloced(p) ){
    sqlite3DbFree(p->db, p->zText);
    p->printfFlags &= ~SQLITE_PRINTF_MALLOCED;
  }
  p->zText = 0;
}

  p->db = db;
  p->nAlloc = n;
  p->mxAlloc = mx;
  p->nChar = 0;
  p->accError = 0;
  p->printfFlags = 0;
}

/* Allocate and initialize a new dynamic string object */
sqlite3_str *sqlite3_str_new(sqlite3 *db){
  sqlite3_str *p = sqlite3DbMallocRaw(db, sizeof(*p));
  if( p ){
    sqlite3StrAccumInit(p, db, 0, 0, SQLITE_MAX_LENGTH);
  }
  return p;
}

/*
** Print into memory obtained from sqliteMalloc().  Use the internal
** %-conversion extensions.
*/
char *sqlite3VMPrintf(sqlite3 *db, const char *zFormat, va_list ap){
  char *z;
  char zBase[SQLITE_PRINT_BUF_SIZE];
  StrAccum acc;
  assert( db!=0 );
  sqlite3StrAccumInit(&acc, db, zBase, sizeof(zBase),
                      db->aLimit[SQLITE_LIMIT_LENGTH]);
  acc.printfFlags = SQLITE_PRINTF_INTERNAL;
  sqlite3_str_vappendf(&acc, zFormat, ap);
  z = sqlite3StrAccumFinish(&acc);
  if( acc.accError==SQLITE_NOMEM ){
    sqlite3OomFault(db);
  }
  return z;
}

/*
** Print into memory obtained from sqliteMalloc().  Use the internal

    return 0;
  }
#endif
#ifndef SQLITE_OMIT_AUTOINIT
  if( sqlite3_initialize() ) return 0;
#endif
  sqlite3StrAccumInit(&acc, 0, zBase, sizeof(zBase), SQLITE_MAX_LENGTH);
  sqlite3_str_vappendf(&acc, zFormat, ap);
  z = sqlite3StrAccumFinish(&acc);
  return z;
}

/*
** Print into memory obtained from sqlite3_malloc()().  Omit the internal
** %-conversion extensions.

  if( zBuf==0 || zFormat==0 ) {
    (void)SQLITE_MISUSE_BKPT;
    if( zBuf ) zBuf[0] = 0;
    return zBuf;
  }
#endif
  sqlite3StrAccumInit(&acc, 0, zBuf, n, 0);
  sqlite3_str_vappendf(&acc, zFormat, ap);
  zBuf[acc.nChar] = 0;
  return zBuf;
}
char *sqlite3_snprintf(int n, char *zBuf, const char *zFormat, ...){
  char *z;
  va_list ap;
  va_start(ap,zFormat);

** We house it in a separate routine from sqlite3_log() to avoid using
** stack space on small-stack systems when logging is disabled.
**
** sqlite3_log() must render into a static buffer.  It cannot dynamically
** allocate memory because it might be called while the memory allocator
** mutex is held.
**
** sqlite3_str_vappendf() might ask for *temporary* memory allocations for
** certain format characters (%q) or for very large precisions or widths.
** Care must be taken that any sqlite3_log() calls that occur while the
** memory mutex is held do not use these mechanisms.
*/
static void renderLogMsg(int iErrCode, const char *zFormat, va_list ap){
  StrAccum acc;                          /* String accumulator */
  char zMsg[SQLITE_PRINT_BUF_SIZE*3];    /* Complete log message */

  sqlite3StrAccumInit(&acc, 0, zMsg, sizeof(zMsg), 0);
  sqlite3_str_vappendf(&acc, zFormat, ap);
  sqlite3GlobalConfig.xLog(sqlite3GlobalConfig.pLogArg, iErrCode,
                           sqlite3StrAccumFinish(&acc));
}

/*
** Format and write a message to the log if logging is enabled.
*/

*/
void sqlite3DebugPrintf(const char *zFormat, ...){
  va_list ap;
  StrAccum acc;
  char zBuf[500];
  sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
  va_start(ap,zFormat);
  sqlite3_str_vappendf(&acc, zFormat, ap);
  va_end(ap);
  sqlite3StrAccumFinish(&acc);
#ifdef SQLITE_OS_TRACE_PROC
  {
    extern void SQLITE_OS_TRACE_PROC(const char *zBuf, int nBuf);
    SQLITE_OS_TRACE_PROC(zBuf, sizeof(zBuf));
  }
#else
  fprintf(stdout,"%s", zBuf);
  fflush(stdout);
#endif
}
#endif


/*
** variable-argument wrapper around sqlite3_str_vappendf(). The bFlags argument
** can contain the bit SQLITE_PRINTF_INTERNAL enable internal formats.
*/
void sqlite3_str_appendf(StrAccum *p, const char *zFormat, ...){
  va_list ap;
  va_start(ap,zFormat);
  sqlite3_str_vappendf(p, zFormat, ap);
  va_end(ap);
}

** SQLite is compiled with the [-DSQLITE_OMIT_VACUUM] option.  Also,
** new keywords may be added to future releases of SQLite.
*/
int sqlite3_keyword_count(void);
int sqlite3_keyword_name(int,const char**,int*);
int sqlite3_keyword_check(const char*,int);

/*
** CAPI3REF: Dynamic String Object
** KEYWORDS: {dynamic string}
**
** An instance of the sqlite3_str object contains a dynamically-sized
** string under construction.
**
** The lifecycle of an sqlite3_str object is as follows:
** <ol>
** <li> The sqlite3_str object is created using [sqlite3_str_new()].
** <li> Text is appended to the sqlite3_str object using various
** methods, such as [sqlite3_str_appendf()].
** <li> The sqlite3_str object is destroyed and the string it created
** is returned using the [sqlite3_str_finish()] interface.
** </ol>
*/
typedef struct sqlite3_str sqlite3_str;

/*
** CAPI3REF: Create A New Dynamic String Object
** CONSTRUCTOR: sqlite3_str
**
** The [sqlite3_str_new(D)] allocates and initializes a new [sqlite3_str]
** object.  The [sqlite3_str_new(D)] interface returns NULL on an out-of-memory
** condition.  To avoid memory leaks, the object returned by
** [sqlite3_str_new(D)] must be freed by a subsequent call to 
** [sqlite3_str_finish(S)].
**
** If the D argument to [sqlite3_str_new(D)] is NULL then memory used to
** construct the string is always taken from the global memory pool used
** by [sqlite3_malloc64()].  If D is not NULL, then a private memory pool
** used by connection D might also be used.  This private memory pool is
** faster, but is limited in space, and should only be used for transient
** allocations.  The final string returned by [sqlite3_str_finish(X)] is
** always stored in space obtained from [sqlite3_malloc64()] regardless
** of whether or not the private per-connection memory pool is used during
** its construction.
*/
sqlite3_str *sqlite3_str_new(sqlite3*);

/*
** CAPI3REF: Finalize A Dynamic String
** DESTRUCTOR: sqlite3_str
**
** The [sqlite3_str_finish(X)] interface destroys the sqlite3_str object X
** and returns a pointer to a memory buffer obtained from [sqlite3_malloc64()]
** that contains the constructed string.  The calling application should
** pass the returned value to [sqlite3_free()] to avoid a memory leak.
** The [sqlite3_str_finish(X)] interface may return a NULL pointer if any
** errors were encountered during construction of the string.  The
** [sqlite3_str_finish(X)] interface will also return a NULL pointer if the
** string in [sqlite3_str] object X is zero bytes long.
*/
char *sqlite3_str_finish(sqlite3_str*);

/*
** CAPI3REF: Add Content To A Dynamic String
** METHOD: sqlite3_str
**
** These interfaces add content to an sqlite3_str object previously obtained
** from [sqlite3_str_new()].
**
** The [sqlite3_str_appendf(X,F,...)] and 
** [sqlite3_str_vappendf(X,F,V)] interfaces uses the [built-in printf]
** functionality of SQLite to append formatted text onto the end of 
** [sqlite3_str] object X.
**
** The [sqlite3_str_append(X,S,N)] method appends exactly N bytes from string S
** onto the end of the [sqlite3_str] object X.  N must be non-negative.
** S must contain at least N non-zero bytes of content.  To append a
** zero-terminated string in its entirety, use the [sqlite3_str_appendall()]
** method instead.
**
** The [sqlite3_str_appendall(X,S)] method the complete content of
** zero-terminated string S onto the end of [sqlite3_str] object X.
**
** The [sqlite3_str_appendchar(X,N,C)] method appends N copies of the
** single-byte character C onto the end of [sqlite3_str] object X.
** This method can be used, for example, to add whitespace indentation.
**
** The [sqlite3_str_reset(X)] method resets the string under construction
** inside [sqlite3_str] object X back to zero bytes in length.  
**
** These methods do not return a result code.  If an error occurs, that fact
** is recorded in the [sqlite3_str] object and can be recovered by a
** subsequent call to [sqlite3_str_errcode(X)].
*/
void sqlite3_str_appendf(sqlite3_str*, const char *zFormat, ...);
void sqlite3_str_vappendf(sqlite3_str*, const char *zFormat, va_list);
void sqlite3_str_append(sqlite3_str*, const char *zIn, int N);
void sqlite3_str_appendall(sqlite3_str*, const char *zIn);
void sqlite3_str_appendchar(sqlite3_str*, int N, char C);
void sqlite3_str_reset(sqlite3_str*);

/*
** CAPI3REF: Status Of A Dynamic String
** METHOD: sqlite3_str
**
** These interfaces return the current status of an [sqlite3_str] object.
**
** If any prior errors have occurred while constructing the dynamic string
** in sqlite3_str X, then the [sqlite3_str_errcode(X)] method will return
** an appropriate error code.  The [sqlite3_str_errcode(X)] method returns
** [SQLITE_NOMEM] following any out-of-memory error, or
** [SQLITE_TOOBIG] if the size of the dynamic string exceeds
** [SQLITE_MAX_LENGTH], or [SQLITE_OK] if there have been no errors.
**
** The [sqlite3_str_length(X)] method returns the current length, in bytes,
** of the dynamic string under construction in [sqlite3_str] object X.
** The length returned by [sqlite3_str_length(X)] does not include the
** zero-termination byte.
**
** The [sqlite3_str_value(X)] method returns a pointer to the current
** content of the dynamic string under construction in X.  The value
** returned by [sqlite3_str_value(X)] is managed by the sqlite3_str object X
** and might be freed or altered by any subsequent method on the same
** [sqlite3_str] object.  Applications must not used the pointer returned
** [sqlite3_str_value(X)] after any subsequent method call on the same
** object.  Applications may change the content of the string returned
** by [sqlite3_str_value(X)] as long as they do not write into any bytes
** outside the range of 0 to [sqlite3_str_length(X)] and do not read or
** write any byte after any subsequent sqlite3_str method call.
*/
int sqlite3_str_errcode(sqlite3_str*);
int sqlite3_str_length(sqlite3_str*);
char *sqlite3_str_value(sqlite3_str*);

/*
** CAPI3REF: SQLite Runtime Status
**
** ^These interfaces are used to retrieve runtime status information
** about the performance of SQLite, and optionally to reset various
** highwater marks.  ^The first argument is an integer code for
** the specific parameter to measure.  ^(Recognized integer codes

typedef struct PrintfArguments PrintfArguments;
typedef struct RowSet RowSet;
typedef struct Savepoint Savepoint;
typedef struct Select Select;
typedef struct SQLiteThread SQLiteThread;
typedef struct SelectDest SelectDest;
typedef struct SrcList SrcList;
typedef struct sqlite3_str StrAccum; /* Internal alias for sqlite3_str */
typedef struct Table Table;
typedef struct TableLock TableLock;
typedef struct Token Token;
typedef struct TreeView TreeView;
typedef struct Trigger Trigger;
typedef struct TriggerPrg TriggerPrg;
typedef struct TriggerStep TriggerStep;

  const Token *pName; /* Name of the container - used for error messages */
};

/*
** An objected used to accumulate the text of a string where we
** do not necessarily know how big the string will be in the end.
*/
struct sqlite3_str {
  sqlite3 *db;         /* Optional database for lookaside.  Can be NULL */
  char *zText;         /* The string collected so far */
  u32  nAlloc;         /* Amount of space allocated in zText */
  u32  mxAlloc;        /* Maximum allowed allocation.  0 for no malloc usage */
  u32  nChar;          /* Length of the string so far */
  u8   accError;       /* SQLITE_NOMEM or SQLITE_TOOBIG */
  u8   printfFlags;    /* SQLITE_PRINTF flags below */
};


#define SQLITE_PRINTF_INTERNAL 0x01  /* Internal-use-only converters allowed */
#define SQLITE_PRINTF_SQLFUNC  0x02  /* SQL function arguments to VXPrintf */
#define SQLITE_PRINTF_MALLOCED 0x04  /* True if xText is allocated space */

#define isMalloced(X)  (((X)->printfFlags & SQLITE_PRINTF_MALLOCED)!=0)

*/
struct PrintfArguments {
  int nArg;                /* Total number of arguments */
  int nUsed;               /* Number of arguments used so far */
  sqlite3_value **apArg;   /* The argument values */
};



char *sqlite3MPrintf(sqlite3*,const char*, ...);
char *sqlite3VMPrintf(sqlite3*,const char*, va_list);
#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
  void sqlite3DebugPrintf(const char*, ...);
#endif
#if defined(SQLITE_TEST)
  void *sqlite3TestTextToPtr(const char*);

);
void sqlite3OomFault(sqlite3*);
void sqlite3OomClear(sqlite3*);
int sqlite3ApiExit(sqlite3 *db, int);
int sqlite3OpenTempDatabase(Parse *);

void sqlite3StrAccumInit(StrAccum*, sqlite3*, char*, int, int);



char *sqlite3StrAccumFinish(StrAccum*);

void sqlite3SelectDestInit(SelectDest*,int,int);
Expr *sqlite3CreateColumnExpr(sqlite3 *, SrcList *, int, int);

void sqlite3BackupRestart(sqlite3_backup *);
void sqlite3BackupUpdate(sqlite3_backup *, Pgno, const u8 *);

#ifndef SQLITE_OMIT_SUBQUERY

  va_list ap;
  int i;
  StrAccum acc;
  char zBuf[500];
  sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
  if( p ){
    for(i=0; i<p->iLevel && i<sizeof(p->bLine)-1; i++){
      sqlite3_str_append(&acc, p->bLine[i] ? "|   " : "    ", 4);
    }
    sqlite3_str_append(&acc, p->bLine[i] ? "|-- " : "'-- ", 4);
  }
  if( zFormat!=0 ){
    va_start(ap, zFormat);
    sqlite3_str_vappendf(&acc, zFormat, ap);
    va_end(ap);
    assert( acc.nChar>0 );
    sqlite3_str_append(&acc, "\n", 1);
  }
  sqlite3StrAccumFinish(&acc);
  fprintf(stdout,"%s", zBuf);
  fflush(stdout);
}

/*

  if( pWith->nCte>0 ){
    pView = sqlite3TreeViewPush(pView, 1);
    for(i=0; i<pWith->nCte; i++){
      StrAccum x;
      char zLine[1000];
      const struct Cte *pCte = &pWith->a[i];
      sqlite3StrAccumInit(&x, 0, zLine, sizeof(zLine), 0);
      sqlite3_str_appendf(&x, "%s", pCte->zName);
      if( pCte->pCols && pCte->pCols->nExpr>0 ){
        char cSep = '(';
        int j;
        for(j=0; j<pCte->pCols->nExpr; j++){
          sqlite3_str_appendf(&x, "%c%s", cSep, pCte->pCols->a[j].zName);
          cSep = ',';
        }
        sqlite3_str_appendf(&x, ")");
      }
      sqlite3_str_appendf(&x, " AS");
      sqlite3StrAccumFinish(&x);
      sqlite3TreeViewItem(pView, zLine, i<pWith->nCte-1);
      sqlite3TreeViewSelect(pView, pCte->pSelect, 0);
      sqlite3TreeViewPop(pView);
    }
    sqlite3TreeViewPop(pView);
  }

      pView = sqlite3TreeViewPush(pView, (n--)>0);
      sqlite3TreeViewLine(pView, "FROM");
      for(i=0; i<p->pSrc->nSrc; i++){
        struct SrcList_item *pItem = &p->pSrc->a[i];
        StrAccum x;
        char zLine[100];
        sqlite3StrAccumInit(&x, 0, zLine, sizeof(zLine), 0);
        sqlite3_str_appendf(&x, "{%d,*}", pItem->iCursor);
        if( pItem->zDatabase ){
          sqlite3_str_appendf(&x, " %s.%s", pItem->zDatabase, pItem->zName);
        }else if( pItem->zName ){
          sqlite3_str_appendf(&x, " %s", pItem->zName);
        }
        if( pItem->pTab ){
          sqlite3_str_appendf(&x, " tabname=%Q", pItem->pTab->zName);
        }
        if( pItem->zAlias ){
          sqlite3_str_appendf(&x, " (AS %s)", pItem->zAlias);
        }
        if( pItem->fg.jointype & JT_LEFT ){
          sqlite3_str_appendf(&x, " LEFT-JOIN");
        }
        sqlite3StrAccumFinish(&x);
        sqlite3TreeViewItem(pView, zLine, i<p->pSrc->nSrc-1); 
        if( pItem->pSelect ){
          sqlite3TreeViewSelect(pView, pItem->pSelect, 0);
        }
        if( pItem->fg.isTabFunc ){

** Translate the P4.pExpr value for an OP_CursorHint opcode into text
** that can be displayed in the P4 column of EXPLAIN output.
*/
static void displayP4Expr(StrAccum *p, Expr *pExpr){
  const char *zOp = 0;
  switch( pExpr->op ){
    case TK_STRING:
      sqlite3_str_appendf(p, "%Q", pExpr->u.zToken);
      break;
    case TK_INTEGER:
      sqlite3_str_appendf(p, "%d", pExpr->u.iValue);
      break;
    case TK_NULL:
      sqlite3_str_appendf(p, "NULL");
      break;
    case TK_REGISTER: {
      sqlite3_str_appendf(p, "r[%d]", pExpr->iTable);
      break;
    }
    case TK_COLUMN: {
      if( pExpr->iColumn<0 ){
        sqlite3_str_appendf(p, "rowid");
      }else{
        sqlite3_str_appendf(p, "c%d", (int)pExpr->iColumn);
      }
      break;
    }
    case TK_LT:      zOp = "LT";      break;
    case TK_LE:      zOp = "LE";      break;
    case TK_GT:      zOp = "GT";      break;
    case TK_GE:      zOp = "GE";      break;

    case TK_UPLUS:   zOp = "PLUS";    break;
    case TK_BITNOT:  zOp = "BITNOT";  break;
    case TK_NOT:     zOp = "NOT";     break;
    case TK_ISNULL:  zOp = "ISNULL";  break;
    case TK_NOTNULL: zOp = "NOTNULL"; break;

    default:
      sqlite3_str_appendf(p, "%s", "expr");
      break;
  }

  if( zOp ){
    sqlite3_str_appendf(p, "%s(", zOp);
    displayP4Expr(p, pExpr->pLeft);
    if( pExpr->pRight ){
      sqlite3_str_append(p, ",", 1);
      displayP4Expr(p, pExpr->pRight);
    }
    sqlite3_str_append(p, ")", 1);
  }
}
#endif /* VDBE_DISPLAY_P4 && defined(SQLITE_ENABLE_CURSOR_HINTS) */


#if VDBE_DISPLAY_P4
/*
** Compute a string that describes the P4 parameter for an opcode.
** Use zTemp for any required temporary buffer space.
*/
static char *displayP4(Op *pOp, char *zTemp, int nTemp){
  char *zP4 = zTemp;
  StrAccum x;
  assert( nTemp>=20 );
  sqlite3StrAccumInit(&x, 0, zTemp, nTemp, 0);
  switch( pOp->p4type ){
    case P4_KEYINFO: {
      int j;
      KeyInfo *pKeyInfo = pOp->p4.pKeyInfo;
      assert( pKeyInfo->aSortOrder!=0 );
      sqlite3_str_appendf(&x, "k(%d", pKeyInfo->nKeyField);
      for(j=0; j<pKeyInfo->nKeyField; j++){
        CollSeq *pColl = pKeyInfo->aColl[j];
        const char *zColl = pColl ? pColl->zName : "";
        if( strcmp(zColl, "BINARY")==0 ) zColl = "B";
        sqlite3_str_appendf(&x, ",%s%s", 
               pKeyInfo->aSortOrder[j] ? "-" : "", zColl);
      }
      sqlite3_str_append(&x, ")", 1);
      break;
    }
#ifdef SQLITE_ENABLE_CURSOR_HINTS
    case P4_EXPR: {
      displayP4Expr(&x, pOp->p4.pExpr);
      break;
    }
#endif
    case P4_COLLSEQ: {
      CollSeq *pColl = pOp->p4.pColl;
      sqlite3_str_appendf(&x, "(%.20s)", pColl->zName);
      break;
    }
    case P4_FUNCDEF: {
      FuncDef *pDef = pOp->p4.pFunc;
      sqlite3_str_appendf(&x, "%s(%d)", pDef->zName, pDef->nArg);
      break;
    }
#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
    case P4_FUNCCTX: {
      FuncDef *pDef = pOp->p4.pCtx->pFunc;
      sqlite3_str_appendf(&x, "%s(%d)", pDef->zName, pDef->nArg);
      break;
    }
#endif
    case P4_INT64: {
      sqlite3_str_appendf(&x, "%lld", *pOp->p4.pI64);
      break;
    }
    case P4_INT32: {
      sqlite3_str_appendf(&x, "%d", pOp->p4.i);
      break;
    }
    case P4_REAL: {
      sqlite3_str_appendf(&x, "%.16g", *pOp->p4.pReal);
      break;
    }
    case P4_MEM: {
      Mem *pMem = pOp->p4.pMem;
      if( pMem->flags & MEM_Str ){
        zP4 = pMem->z;
      }else if( pMem->flags & MEM_Int ){
        sqlite3_str_appendf(&x, "%lld", pMem->u.i);
      }else if( pMem->flags & MEM_Real ){
        sqlite3_str_appendf(&x, "%.16g", pMem->u.r);
      }else if( pMem->flags & MEM_Null ){
        zP4 = "NULL";
      }else{
        assert( pMem->flags & MEM_Blob );
        zP4 = "(blob)";
      }
      break;
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    case P4_VTAB: {
      sqlite3_vtab *pVtab = pOp->p4.pVtab->pVtab;
      sqlite3_str_appendf(&x, "vtab:%p", pVtab);
      break;
    }
#endif
    case P4_INTARRAY: {
      int i;
      int *ai = pOp->p4.ai;
      int n = ai[0];   /* The first element of an INTARRAY is always the
                       ** count of the number of elements to follow */
      for(i=1; i<=n; i++){
        sqlite3_str_appendf(&x, ",%d", ai[i]);
      }
      zTemp[0] = '[';
      sqlite3_str_append(&x, "]", 1);
      break;
    }
    case P4_SUBPROGRAM: {
      sqlite3_str_appendf(&x, "program");
      break;
    }
    case P4_DYNBLOB:
    case P4_ADVANCE: {
      zTemp[0] = 0;
      break;
    }
    case P4_TABLE: {
      sqlite3_str_appendf(&x, "%s", pOp->p4.pTab->zName);
      break;
    }
    default: {
      zP4 = pOp->p4.z;
      if( zP4==0 ){
        zP4 = zTemp;
        zTemp[0] = 0;

  db = p->db;
  sqlite3StrAccumInit(&out, 0, zBase, sizeof(zBase), 
                      db->aLimit[SQLITE_LIMIT_LENGTH]);
  if( db->nVdbeExec>1 ){
    while( *zRawSql ){
      const char *zStart = zRawSql;
      while( *(zRawSql++)!='\n' && *zRawSql );
      sqlite3_str_append(&out, "-- ", 3);
      assert( (zRawSql - zStart) > 0 );
      sqlite3_str_append(&out, zStart, (int)(zRawSql-zStart));
    }
  }else if( p->nVar==0 ){
    sqlite3_str_append(&out, zRawSql, sqlite3Strlen30(zRawSql));
  }else{
    while( zRawSql[0] ){
      n = findNextHostParameter(zRawSql, &nToken);
      assert( n>0 );
      sqlite3_str_append(&out, zRawSql, n);
      zRawSql += n;
      assert( zRawSql[0] || nToken==0 );
      if( nToken==0 ) break;
      if( zRawSql[0]=='?' ){
        if( nToken>1 ){
          assert( sqlite3Isdigit(zRawSql[1]) );
          sqlite3GetInt32(&zRawSql[1], &idx);

        assert( idx>0 );
      }
      zRawSql += nToken;
      nextIndex = idx + 1;
      assert( idx>0 && idx<=p->nVar );
      pVar = &p->aVar[idx-1];
      if( pVar->flags & MEM_Null ){
        sqlite3_str_append(&out, "NULL", 4);
      }else if( pVar->flags & MEM_Int ){
        sqlite3_str_appendf(&out, "%lld", pVar->u.i);
      }else if( pVar->flags & MEM_Real ){
        sqlite3_str_appendf(&out, "%!.15g", pVar->u.r);
      }else if( pVar->flags & MEM_Str ){
        int nOut;  /* Number of bytes of the string text to include in output */
#ifndef SQLITE_OMIT_UTF16
        u8 enc = ENC(db);
        if( enc!=SQLITE_UTF8 ){
          memset(&utf8, 0, sizeof(utf8));
          utf8.db = db;
          sqlite3VdbeMemSetStr(&utf8, pVar->z, pVar->n, enc, SQLITE_STATIC);
          if( SQLITE_NOMEM==sqlite3VdbeChangeEncoding(&utf8, SQLITE_UTF8) ){
            out.accError = SQLITE_NOMEM;
            out.nAlloc = 0;
          }
          pVar = &utf8;
        }
#endif
        nOut = pVar->n;
#ifdef SQLITE_TRACE_SIZE_LIMIT
        if( nOut>SQLITE_TRACE_SIZE_LIMIT ){
          nOut = SQLITE_TRACE_SIZE_LIMIT;
          while( nOut<pVar->n && (pVar->z[nOut]&0xc0)==0x80 ){ nOut++; }
        }
#endif    
        sqlite3_str_appendf(&out, "'%.*q'", nOut, pVar->z);
#ifdef SQLITE_TRACE_SIZE_LIMIT
        if( nOut<pVar->n ){
          sqlite3_str_appendf(&out, "/*+%d bytes*/", pVar->n-nOut);
        }
#endif
#ifndef SQLITE_OMIT_UTF16
        if( enc!=SQLITE_UTF8 ) sqlite3VdbeMemRelease(&utf8);
#endif
      }else if( pVar->flags & MEM_Zero ){
        sqlite3_str_appendf(&out, "zeroblob(%d)", pVar->u.nZero);
      }else{
        int nOut;  /* Number of bytes of the blob to include in output */
        assert( pVar->flags & MEM_Blob );
        sqlite3_str_append(&out, "x'", 2);
        nOut = pVar->n;
#ifdef SQLITE_TRACE_SIZE_LIMIT
        if( nOut>SQLITE_TRACE_SIZE_LIMIT ) nOut = SQLITE_TRACE_SIZE_LIMIT;
#endif
        for(i=0; i<nOut; i++){
          sqlite3_str_appendf(&out, "%02x", pVar->z[i]&0xff);
        }
        sqlite3_str_append(&out, "'", 1);
#ifdef SQLITE_TRACE_SIZE_LIMIT
        if( nOut<pVar->n ){
          sqlite3_str_appendf(&out, "/*+%d bytes*/", pVar->n-nOut);
        }
#endif
      }
    }
  }
  if( out.accError ) sqlite3_str_reset(&out);
  return sqlite3StrAccumFinish(&out);
}

#endif /* #ifndef SQLITE_OMIT_TRACE */

  int iTerm,                  /* Zero-based index of first term. */
  int bAnd,                   /* Non-zero to append " AND " */
  const char *zOp             /* Name of the operator */
){
  int i;

  assert( nTerm>=1 );
  if( bAnd ) sqlite3_str_append(pStr, " AND ", 5);

  if( nTerm>1 ) sqlite3_str_append(pStr, "(", 1);
  for(i=0; i<nTerm; i++){
    if( i ) sqlite3_str_append(pStr, ",", 1);
    sqlite3_str_appendall(pStr, explainIndexColumnName(pIdx, iTerm+i));
  }
  if( nTerm>1 ) sqlite3_str_append(pStr, ")", 1);

  sqlite3_str_append(pStr, zOp, 1);

  if( nTerm>1 ) sqlite3_str_append(pStr, "(", 1);
  for(i=0; i<nTerm; i++){
    if( i ) sqlite3_str_append(pStr, ",", 1);
    sqlite3_str_append(pStr, "?", 1);
  }
  if( nTerm>1 ) sqlite3_str_append(pStr, ")", 1);
}

/*
** Argument pLevel describes a strategy for scanning table pTab. This 
** function appends text to pStr that describes the subset of table
** rows scanned by the strategy in the form of an SQL expression.
**

static void explainIndexRange(StrAccum *pStr, WhereLoop *pLoop){
  Index *pIndex = pLoop->u.btree.pIndex;
  u16 nEq = pLoop->u.btree.nEq;
  u16 nSkip = pLoop->nSkip;
  int i, j;

  if( nEq==0 && (pLoop->wsFlags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ) return;
  sqlite3_str_append(pStr, " (", 2);
  for(i=0; i<nEq; i++){
    const char *z = explainIndexColumnName(pIndex, i);
    if( i ) sqlite3_str_append(pStr, " AND ", 5);
    sqlite3_str_appendf(pStr, i>=nSkip ? "%s=?" : "ANY(%s)", z);
  }

  j = i;
  if( pLoop->wsFlags&WHERE_BTM_LIMIT ){
    explainAppendTerm(pStr, pIndex, pLoop->u.btree.nBtm, j, i, ">");
    i = 1;
  }
  if( pLoop->wsFlags&WHERE_TOP_LIMIT ){
    explainAppendTerm(pStr, pIndex, pLoop->u.btree.nTop, j, i, "<");
  }
  sqlite3_str_append(pStr, ")", 1);
}

/*
** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
** command, or if either SQLITE_DEBUG or SQLITE_ENABLE_STMT_SCANSTATUS was
** defined at compile-time. If it is not a no-op, a single OP_Explain opcode 
** is added to the output to describe the table scan strategy in pLevel.

    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_OR_SUBCLAUSE) ) return 0;

    isSearch = (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
            || ((flags&WHERE_VIRTUALTABLE)==0 && (pLoop->u.btree.nEq>0))
            || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));

    sqlite3StrAccumInit(&str, db, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
    sqlite3_str_appendall(&str, isSearch ? "SEARCH" : "SCAN");
    if( pItem->pSelect ){
      sqlite3_str_appendf(&str, " SUBQUERY 0x%p", pItem->pSelect);
    }else{
      sqlite3_str_appendf(&str, " TABLE %s", pItem->zName);
    }

    if( pItem->zAlias ){
      sqlite3_str_appendf(&str, " AS %s", pItem->zAlias);
    }
    if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
      const char *zFmt = 0;
      Index *pIdx;

      assert( pLoop->u.btree.pIndex!=0 );
      pIdx = pLoop->u.btree.pIndex;

        zFmt = "AUTOMATIC COVERING INDEX";
      }else if( flags & WHERE_IDX_ONLY ){
        zFmt = "COVERING INDEX %s";
      }else{
        zFmt = "INDEX %s";
      }
      if( zFmt ){
        sqlite3_str_append(&str, " USING ", 7);
        sqlite3_str_appendf(&str, zFmt, pIdx->zName);
        explainIndexRange(&str, pLoop);
      }
    }else if( (flags & WHERE_IPK)!=0 && (flags & WHERE_CONSTRAINT)!=0 ){
      const char *zRangeOp;
      if( flags&(WHERE_COLUMN_EQ|WHERE_COLUMN_IN) ){
        zRangeOp = "=";
      }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
        zRangeOp = ">? AND rowid<";
      }else if( flags&WHERE_BTM_LIMIT ){
        zRangeOp = ">";
      }else{
        assert( flags&WHERE_TOP_LIMIT);
        zRangeOp = "<";
      }
      sqlite3_str_appendf(&str, 
          " USING INTEGER PRIMARY KEY (rowid%s?)",zRangeOp);
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
      sqlite3_str_appendf(&str, " VIRTUAL TABLE INDEX %d:%s",
                  pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
    }
#endif
#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
    if( pLoop->nOut>=10 ){
      sqlite3_str_appendf(&str, " (~%llu rows)",
             sqlite3LogEstToInt(pLoop->nOut));
    }else{
      sqlite3_str_append(&str, " (~1 row)", 9);
    }
#endif
    zMsg = sqlite3StrAccumFinish(&str);
    ret = sqlite3VdbeAddOp4(v, OP_Explain, sqlite3VdbeCurrentAddr(v),
                            pParse->addrExplain, 0, zMsg,P4_DYNAMIC);
  }
  return ret;