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Overview
Comment:The bytecode() function now runs and sometimes works, but it untested and there are known problems.
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Timelines: family | ancestors | descendants | both | bytecode-function
Files: files | file ages | folders
SHA3-256: 6819b86eb2de516c445655a83f9b2ba5ae0bff660cffaf84f1345d9be79b051e
User & Date: drh 2020-03-23 20:58:55.887
Context
2020-03-23
23:17
Fix the build so that it works even without SQLITE_ENABLE_EXPLAIN_COMMENTS. (check-in: 5896cbf4d0 user: drh tags: bytecode-function)
20:58
The bytecode() function now runs and sometimes works, but it untested and there are known problems. (check-in: 6819b86eb2 user: drh tags: bytecode-function)
19:14
Further simplification and modularization of the EXPLAIN logic. (check-in: aee1c12f42 user: drh tags: bytecode-function)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/vdbeInt.h.
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#endif

/*
** VDBE_DISPLAY_P4 is true or false depending on whether or not the
** "explain" P4 display logic is enabled.
*/
#if !defined(SQLITE_OMIT_EXPLAIN) || !defined(NDEBUG) \
     || defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)

# define VDBE_DISPLAY_P4 1
#else
# define VDBE_DISPLAY_P4 0
#endif

/*
** SQL is translated into a sequence of instructions to be







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#endif

/*
** VDBE_DISPLAY_P4 is true or false depending on whether or not the
** "explain" P4 display logic is enabled.
*/
#if !defined(SQLITE_OMIT_EXPLAIN) || !defined(NDEBUG) \
     || defined(VDBE_PROFILE) || defined(SQLITE_DEBUG) \
     || defined(SQLITE_ENABLE_BYTECODE_VTAB)
# define VDBE_DISPLAY_P4 1
#else
# define VDBE_DISPLAY_P4 0
#endif

/*
** SQL is translated into a sequence of instructions to be
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u32 sqlite3VdbeSerialGet(const unsigned char*, u32, Mem*);
void sqlite3VdbeDeleteAuxData(sqlite3*, AuxData**, int, int);

int sqlite2BtreeKeyCompare(BtCursor *, const void *, int, int, int *);
int sqlite3VdbeIdxKeyCompare(sqlite3*,VdbeCursor*,UnpackedRecord*,int*);
int sqlite3VdbeIdxRowid(sqlite3*, BtCursor*, i64*);
int sqlite3VdbeExec(Vdbe*);
#ifndef SQLITE_OMIT_EXPLAIN
int sqlite3VdbeNextOpcode(Vdbe*,Mem*,int,int*,int*,Op**);




int sqlite3VdbeList(Vdbe*);
#endif
int sqlite3VdbeHalt(Vdbe*);
int sqlite3VdbeChangeEncoding(Mem *, int);
int sqlite3VdbeMemTooBig(Mem*);
int sqlite3VdbeMemCopy(Mem*, const Mem*);
void sqlite3VdbeMemShallowCopy(Mem*, const Mem*, int);







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u32 sqlite3VdbeSerialGet(const unsigned char*, u32, Mem*);
void sqlite3VdbeDeleteAuxData(sqlite3*, AuxData**, int, int);

int sqlite2BtreeKeyCompare(BtCursor *, const void *, int, int, int *);
int sqlite3VdbeIdxKeyCompare(sqlite3*,VdbeCursor*,UnpackedRecord*,int*);
int sqlite3VdbeIdxRowid(sqlite3*, BtCursor*, i64*);
int sqlite3VdbeExec(Vdbe*);
#if !defined(SQLITE_OMIT_EXPLAIN) || defined(SQLITE_ENABLE_BYTECODE_VTAB)
int sqlite3VdbeNextOpcode(Vdbe*,Mem*,int,int*,int*,Op**);
char *sqlite3VdbeDisplayP4(sqlite3*,Op*);
char *sqlite3VdbeDisplayComment(sqlite3*,const Op*,const char*);
#endif
#if !defined(SQLITE_OMIT_EXPLAIN)
int sqlite3VdbeList(Vdbe*);
#endif
int sqlite3VdbeHalt(Vdbe*);
int sqlite3VdbeChangeEncoding(Mem *, int);
int sqlite3VdbeMemTooBig(Mem*);
int sqlite3VdbeMemCopy(Mem*, const Mem*);
void sqlite3VdbeMemShallowCopy(Mem*, const Mem*, int);
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int sqlite3VdbeMemFromBtree(BtCursor*,u32,u32,Mem*);
int sqlite3VdbeMemFromBtreeZeroOffset(BtCursor*,u32,Mem*);
void sqlite3VdbeMemRelease(Mem *p);
int sqlite3VdbeMemFinalize(Mem*, FuncDef*);
#ifndef SQLITE_OMIT_WINDOWFUNC
int sqlite3VdbeMemAggValue(Mem*, Mem*, FuncDef*);
#endif
#ifndef SQLITE_OMIT_EXPLAIN
const char *sqlite3OpcodeName(int);
#endif
int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve);
int sqlite3VdbeMemClearAndResize(Mem *pMem, int n);
int sqlite3VdbeCloseStatement(Vdbe *, int);
#ifdef SQLITE_DEBUG
int sqlite3VdbeFrameIsValid(VdbeFrame*);







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int sqlite3VdbeMemFromBtree(BtCursor*,u32,u32,Mem*);
int sqlite3VdbeMemFromBtreeZeroOffset(BtCursor*,u32,Mem*);
void sqlite3VdbeMemRelease(Mem *p);
int sqlite3VdbeMemFinalize(Mem*, FuncDef*);
#ifndef SQLITE_OMIT_WINDOWFUNC
int sqlite3VdbeMemAggValue(Mem*, Mem*, FuncDef*);
#endif
#if !defined(SQLITE_OMIT_EXPLAIN) || defined(SQLITE_ENABLE_BYTECODE_VTAB)
const char *sqlite3OpcodeName(int);
#endif
int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve);
int sqlite3VdbeMemClearAndResize(Mem *pMem, int n);
int sqlite3VdbeCloseStatement(Vdbe *, int);
#ifdef SQLITE_DEBUG
int sqlite3VdbeFrameIsValid(VdbeFrame*);
Changes to src/vdbeaux.c.
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** Some translation occurs:
**
**       "PX"      ->  "r[X]"
**       "PX@PY"   ->  "r[X..X+Y-1]"  or "r[x]" if y is 0 or 1
**       "PX@PY+1" ->  "r[X..X+Y]"    or "r[x]" if y is 0
**       "PY..PY"  ->  "r[X..Y]"      or "r[x]" if y<=x
*/
static char *displayComment(
  sqlite3 *db,       /* Optional - Oom error reporting only */
  const Op *pOp,     /* The opcode to be commented */
  const char *zP4    /* Previously obtained value for P4 */
){
  const char *zOpName;
  const char *zSynopsis;
  int nOpName;







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** Some translation occurs:
**
**       "PX"      ->  "r[X]"
**       "PX@PY"   ->  "r[X..X+Y-1]"  or "r[x]" if y is 0 or 1
**       "PX@PY+1" ->  "r[X..X+Y]"    or "r[x]" if y is 0
**       "PY..PY"  ->  "r[X..Y]"      or "r[x]" if y<=x
*/
char *sqlite3VdbeDisplayComment(
  sqlite3 *db,       /* Optional - Oom error reporting only */
  const Op *pOp,     /* The opcode to be commented */
  const char *zP4    /* Previously obtained value for P4 */
){
  const char *zOpName;
  const char *zSynopsis;
  int nOpName;
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#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(sqlite3 *db, Op *pOp){
  char *zP4 = 0;
  StrAccum x;

  sqlite3StrAccumInit(&x, 0, 0, 0, SQLITE_MAX_LENGTH);
  switch( pOp->p4type ){
    case P4_KEYINFO: {
      int j;







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#if VDBE_DISPLAY_P4
/*
** Compute a string that describes the P4 parameter for an opcode.
** Use zTemp for any required temporary buffer space.
*/
char *sqlite3VdbeDisplayP4(sqlite3 *db, Op *pOp){
  char *zP4 = 0;
  StrAccum x;

  sqlite3StrAccumInit(&x, 0, 0, 0, SQLITE_MAX_LENGTH);
  switch( pOp->p4type ){
    case P4_KEYINFO: {
      int j;
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** Print a single opcode.  This routine is used for debugging only.
*/
void sqlite3VdbePrintOp(FILE *pOut, int pc, VdbeOp *pOp){
  char *zP4;
  char *zCom;
  static const char *zFormat1 = "%4d %-13s %4d %4d %4d %-13s %.2X %s\n";
  if( pOut==0 ) pOut = stdout;
  zP4 = displayP4(0, pOp);
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
  zCom = displayComment(0, pOp, zP4);
#else
  zCom = 0;
#endif
  /* NB:  The sqlite3OpcodeName() function is implemented by code created
  ** by the mkopcodeh.awk and mkopcodec.awk scripts which extract the
  ** information from the vdbe.c source text */
  fprintf(pOut, zFormat1, pc, 







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** Print a single opcode.  This routine is used for debugging only.
*/
void sqlite3VdbePrintOp(FILE *pOut, int pc, VdbeOp *pOp){
  char *zP4;
  char *zCom;
  static const char *zFormat1 = "%4d %-13s %4d %4d %4d %-13s %.2X %s\n";
  if( pOut==0 ) pOut = stdout;
  zP4 = sqlite3VdbeDisplayP4(0, pOp);
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
  zCom = sqlite3VdbeDisplayComment(0, pOp, zP4);
#else
  zCom = 0;
#endif
  /* NB:  The sqlite3OpcodeName() function is implemented by code created
  ** by the mkopcodeh.awk and mkopcodec.awk scripts which extract the
  ** information from the vdbe.c source text */
  fprintf(pOut, zFormat1, pc, 
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void sqlite3VdbeFrameMemDel(void *pArg){
  VdbeFrame *pFrame = (VdbeFrame*)pArg;
  assert( sqlite3VdbeFrameIsValid(pFrame) );
  pFrame->pParent = pFrame->v->pDelFrame;
  pFrame->v->pDelFrame = pFrame;
}


/*
** Locate the next opcode to be displayed in EXPLAIN or EXPLAIN
** QUERY PLAN output.
**
** Return SQLITE_ROW on success.  Return SQLITE_DONE if there are no
** more opcodes to be displayed.
*/







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void sqlite3VdbeFrameMemDel(void *pArg){
  VdbeFrame *pFrame = (VdbeFrame*)pArg;
  assert( sqlite3VdbeFrameIsValid(pFrame) );
  pFrame->pParent = pFrame->v->pDelFrame;
  pFrame->v->pDelFrame = pFrame;
}

#if defined(SQLITE_ENABLE_BYTECODE_VTAB) || !defined(SQLITE_OMIT_EXPLAIN)
/*
** Locate the next opcode to be displayed in EXPLAIN or EXPLAIN
** QUERY PLAN output.
**
** Return SQLITE_ROW on success.  Return SQLITE_DONE if there are no
** more opcodes to be displayed.
*/
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    if( aOp[i].opcode==OP_Init && p->pc>1 ) break;
  }
  *piPc = iPc;
  *piAddr = i;
  *paOp = aOp;
  return rc;
}



/*
** Delete a VdbeFrame object and its contents. VdbeFrame objects are
** allocated by the OP_Program opcode in sqlite3VdbeExec().
*/
void sqlite3VdbeFrameDelete(VdbeFrame *p){







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    if( aOp[i].opcode==OP_Init && p->pc>1 ) break;
  }
  *piPc = iPc;
  *piAddr = i;
  *paOp = aOp;
  return rc;
}
#endif /* SQLITE_ENABLE_BYTECODE_VTAB || !SQLITE_OMIT_EXPLAIN */


/*
** Delete a VdbeFrame object and its contents. VdbeFrame objects are
** allocated by the OP_Program opcode in sqlite3VdbeExec().
*/
void sqlite3VdbeFrameDelete(VdbeFrame *p){
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  if( rc==SQLITE_OK ){
    pOp = aOp + i;
    if( db->u1.isInterrupted ){
      p->rc = SQLITE_INTERRUPT;
      rc = SQLITE_ERROR;
      sqlite3VdbeError(p, sqlite3ErrStr(p->rc));
    }else{
      char *zP4 = displayP4(db, pOp);
      if( p->explain==2 ){
        sqlite3VdbeMemSetInt64(pMem, pOp->p1);
        sqlite3VdbeMemSetInt64(pMem+1, pOp->p2);
        sqlite3VdbeMemSetInt64(pMem+2, pOp->p3);
        sqlite3VdbeMemSetStr(pMem+3, zP4, -1, SQLITE_UTF8, sqlite3_free);     
        p->nResColumn = 4;
      }else{
        sqlite3VdbeMemSetInt64(pMem+0, i);
        sqlite3VdbeMemSetStr(pMem+1, (char*)sqlite3OpcodeName(pOp->opcode),
                             -1, SQLITE_UTF8, SQLITE_STATIC);
        sqlite3VdbeMemSetInt64(pMem+2, pOp->p1);
        sqlite3VdbeMemSetInt64(pMem+3, pOp->p2);
        sqlite3VdbeMemSetInt64(pMem+4, pOp->p3);
        /* pMem+5 for p4 is done last */
        sqlite3VdbeMemSetInt64(pMem+6, pOp->p5);
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
        {
          char *zCom = displayComment(db, pOp, zP4);
          sqlite3VdbeMemSetStr(pMem+7, zCom, -1, SQLITE_UTF8, sqlite3_free);
        }
#else
        sqlite3VdbeMemSetNull(pMem+7);
#endif
        sqlite3VdbeMemSetStr(pMem+5, zP4, -1, SQLITE_UTF8, sqlite3_free);
        p->nResColumn = 8;







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  if( rc==SQLITE_OK ){
    pOp = aOp + i;
    if( db->u1.isInterrupted ){
      p->rc = SQLITE_INTERRUPT;
      rc = SQLITE_ERROR;
      sqlite3VdbeError(p, sqlite3ErrStr(p->rc));
    }else{
      char *zP4 = sqlite3VdbeDisplayP4(db, pOp);
      if( p->explain==2 ){
        sqlite3VdbeMemSetInt64(pMem, pOp->p1);
        sqlite3VdbeMemSetInt64(pMem+1, pOp->p2);
        sqlite3VdbeMemSetInt64(pMem+2, pOp->p3);
        sqlite3VdbeMemSetStr(pMem+3, zP4, -1, SQLITE_UTF8, sqlite3_free);     
        p->nResColumn = 4;
      }else{
        sqlite3VdbeMemSetInt64(pMem+0, i);
        sqlite3VdbeMemSetStr(pMem+1, (char*)sqlite3OpcodeName(pOp->opcode),
                             -1, SQLITE_UTF8, SQLITE_STATIC);
        sqlite3VdbeMemSetInt64(pMem+2, pOp->p1);
        sqlite3VdbeMemSetInt64(pMem+3, pOp->p2);
        sqlite3VdbeMemSetInt64(pMem+4, pOp->p3);
        /* pMem+5 for p4 is done last */
        sqlite3VdbeMemSetInt64(pMem+6, pOp->p5);
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
        {
          char *zCom = sqlite3VdbeDisplayComment(db, pOp, zP4);
          sqlite3VdbeMemSetStr(pMem+7, zCom, -1, SQLITE_UTF8, sqlite3_free);
        }
#else
        sqlite3VdbeMemSetNull(pMem+7);
#endif
        sqlite3VdbeMemSetStr(pMem+5, zP4, -1, SQLITE_UTF8, sqlite3_free);
        p->nResColumn = 8;
Changes to src/vdbevtab.c.
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*/
#ifdef SQLITE_ENABLE_BYTECODE_VTAB
#include "sqliteInt.h"
#include "vdbeInt.h"

/* An instance of the bytecode() table-valued function.
*/
typedef struct bytecodevtab_vtab bytecodevtab_vtab;
struct bytecodevtab_vtab {
  sqlite3_vtab base;     /* Base class - must be first */
  sqlite3_stmt *pStmt;   /* The statement whose bytecode is to be displayed */
};

/* A cursor for scanning through the bytecode
*/
typedef struct bytecodevtab_cursor bytecodevtab_cursor;
struct bytecodevtab_cursor {
  sqlite3_vtab_cursor base;  /* Base class - must be first */

  sqlite3_int64 iRowid;      /* The rowid */





};

/*
** Create a new bytecode() table-valued function.
*/
static int bytecodevtabConnect(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  bytecodevtab_vtab *pNew;
  int rc;

  rc = sqlite3_declare_vtab(db,
         "CREATE TABLE x("
           "addr INT,"
           "opcode TEXT,"
           "p1 INT,"







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*/
#ifdef SQLITE_ENABLE_BYTECODE_VTAB
#include "sqliteInt.h"
#include "vdbeInt.h"

/* An instance of the bytecode() table-valued function.
*/
typedef struct bytecodevtab bytecodevtab;
struct bytecodevtab {
  sqlite3_vtab base;     /* Base class - must be first */
  sqlite3 *db;           /* Database connection */
};

/* A cursor for scanning through the bytecode
*/
typedef struct bytecodevtab_cursor bytecodevtab_cursor;
struct bytecodevtab_cursor {
  sqlite3_vtab_cursor base;  /* Base class - must be first */
  sqlite3_stmt *pStmt;       /* The statement whose bytecode is displayed */
  int iRowid;                /* The rowid of the output table */
  int iAddr;                 /* Address */
  int needFinalize;          /* Cursors owns pStmt and must finalize it */
  Op *aOp;                   /* Operand array */
  char *zP4;                 /* Rendered P4 value */
  Mem sub;                   /* Subprograms */
};

/*
** Create a new bytecode() table-valued function.
*/
static int bytecodevtabConnect(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  bytecodevtab *pNew;
  int rc;

  rc = sqlite3_declare_vtab(db,
         "CREATE TABLE x("
           "addr INT,"
           "opcode TEXT,"
           "p1 INT,"
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         ");"
       );
  if( rc==SQLITE_OK ){
    pNew = sqlite3_malloc( sizeof(*pNew) );
    *ppVtab = (sqlite3_vtab*)pNew;
    if( pNew==0 ) return SQLITE_NOMEM;
    memset(pNew, 0, sizeof(*pNew));

  }
  return rc;
}

/*
** This method is the destructor for bytecodevtab_vtab objects.
*/
static int bytecodevtabDisconnect(sqlite3_vtab *pVtab){
  bytecodevtab_vtab *p = (bytecodevtab_vtab*)pVtab;
  sqlite3_free(p);
  return SQLITE_OK;
}

/*
** Constructor for a new bytecodevtab_cursor object.
*/
static int bytecodevtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){

  bytecodevtab_cursor *pCur;
  pCur = sqlite3_malloc( sizeof(*pCur) );
  if( pCur==0 ) return SQLITE_NOMEM;
  memset(pCur, 0, sizeof(*pCur));

  *ppCursor = &pCur->base;
  return SQLITE_OK;
}















/*
** Destructor for a bytecodevtab_cursor.
*/
static int bytecodevtabClose(sqlite3_vtab_cursor *cur){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;

  sqlite3_free(pCur);
  return SQLITE_OK;
}


/*
** Advance a bytecodevtab_cursor to its next row of output.
*/
static int bytecodevtabNext(sqlite3_vtab_cursor *cur){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;



  pCur->iRowid++;







  return SQLITE_OK;
}










/*
** Return values of columns for the row at which the bytecodevtab_cursor
** is currently pointing.
*/
static int bytecodevtabColumn(
  sqlite3_vtab_cursor *cur,   /* The cursor */
  sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
  int i                       /* Which column to return */
){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
#if 0

  switch( i ){
    case TEMPLATEVTAB_A:







      sqlite3_result_int(ctx, 1000 + pCur->iRowid);
      break;

    default:

      assert( i==TEMPLATEVTAB_B );
      sqlite3_result_int(ctx, 2000 + pCur->iRowid);
      break;





  }
#endif










  return SQLITE_OK;
}

/*
** Return the rowid for the current row.  In this implementation, the
** rowid is the same as the output value.
*/
static int bytecodevtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  *pRowid = pCur->iRowid;
  return SQLITE_OK;
}

/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int bytecodevtabEof(sqlite3_vtab_cursor *cur){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  return pCur->iRowid>=10;
}

/*
** This method is called to "rewind" the bytecodevtab_cursor object back
** to the first row of output.  This method is always called at least
** once prior to any call to bytecodevtabColumn() or bytecodevtabRowid() or 
** bytecodevtabEof().
*/
static int bytecodevtabFilter(
  sqlite3_vtab_cursor *pVtabCursor, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor *)pVtabCursor;




  pCur->iRowid = 1;





















  return SQLITE_OK;
}

/*
** SQLite will invoke this method one or more times while planning a query
** that uses the virtual table.  This routine needs to create
** a query plan for each invocation and compute an estimated cost for that


** plan.
*/
static int bytecodevtabBestIndex(
  sqlite3_vtab *tab,
  sqlite3_index_info *pIdxInfo
){


  pIdxInfo->estimatedCost = (double)10;
  pIdxInfo->estimatedRows = 10;









  return SQLITE_OK;
}

/*
** This following structure defines all the methods for the 
** virtual table.
*/
static sqlite3_module bytecodevtabModule = {







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         ");"
       );
  if( rc==SQLITE_OK ){
    pNew = sqlite3_malloc( sizeof(*pNew) );
    *ppVtab = (sqlite3_vtab*)pNew;
    if( pNew==0 ) return SQLITE_NOMEM;
    memset(pNew, 0, sizeof(*pNew));
    pNew->db = db;
  }
  return rc;
}

/*
** This method is the destructor for bytecodevtab objects.
*/
static int bytecodevtabDisconnect(sqlite3_vtab *pVtab){
  bytecodevtab *p = (bytecodevtab*)pVtab;
  sqlite3_free(p);
  return SQLITE_OK;
}

/*
** Constructor for a new bytecodevtab_cursor object.
*/
static int bytecodevtabOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
  bytecodevtab *pVTab = (bytecodevtab*)p;
  bytecodevtab_cursor *pCur;
  pCur = sqlite3_malloc( sizeof(*pCur) );
  if( pCur==0 ) return SQLITE_NOMEM;
  memset(pCur, 0, sizeof(*pCur));
  sqlite3VdbeMemInit(&pCur->sub, pVTab->db, 1);
  *ppCursor = &pCur->base;
  return SQLITE_OK;
}

/*
** Clear all internal content from a bytecodevtab cursor.
*/
static void bytecodevtabCursorClear(bytecodevtab_cursor *pCur){
  sqlite3_free(pCur->zP4);
  pCur->zP4 = 0;
  sqlite3VdbeMemSetNull(&pCur->sub);
  if( pCur->needFinalize ){
    sqlite3_finalize(pCur->pStmt);
  }
  pCur->pStmt = 0;
  pCur->needFinalize = 0;
}

/*
** Destructor for a bytecodevtab_cursor.
*/
static int bytecodevtabClose(sqlite3_vtab_cursor *cur){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  bytecodevtabCursorClear(pCur);
  sqlite3_free(pCur);
  return SQLITE_OK;
}


/*
** Advance a bytecodevtab_cursor to its next row of output.
*/
static int bytecodevtabNext(sqlite3_vtab_cursor *cur){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  int rc;
  if( pCur->zP4 ){
    sqlite3_free(pCur->zP4);
    pCur->zP4 = 0;
  }
  rc = sqlite3VdbeNextOpcode((Vdbe*)pCur->pStmt, &pCur->sub, 0,
                             &pCur->iRowid, &pCur->iAddr, &pCur->aOp);
  if( rc!=SQLITE_OK ){
    sqlite3VdbeMemSetNull(&pCur->sub);
    pCur->aOp = 0;
  }
  return SQLITE_OK;
}

/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int bytecodevtabEof(sqlite3_vtab_cursor *cur){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  return pCur->aOp==0;
}

/*
** Return values of columns for the row at which the bytecodevtab_cursor
** is currently pointing.
*/
static int bytecodevtabColumn(
  sqlite3_vtab_cursor *cur,   /* The cursor */
  sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
  int i                       /* Which column to return */
){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  bytecodevtab *pVTab;
  Op *pOp = pCur->aOp + pCur->iAddr;
  switch( i ){
    case 0:
      sqlite3_result_int(ctx, pCur->iAddr);
      break;
    case 1:
      sqlite3_result_text(ctx, (char*)sqlite3OpcodeName(pOp->opcode),
                          -1, SQLITE_STATIC);
      break;
    case 2:
      sqlite3_result_int(ctx, pOp->p1);
      break;
    case 3:
      sqlite3_result_int(ctx, pOp->p2);
      break;
    case 4:
      sqlite3_result_int(ctx, pOp->p3);
      break;
    case 5:
    case 7:
      pVTab = (bytecodevtab*)cur->pVtab;
      if( pCur->zP4==0 ){
        pCur->zP4 = sqlite3VdbeDisplayP4(pVTab->db, pOp);
      }
      if( i==5 ){
        sqlite3_result_text(ctx, pCur->zP4, -1, SQLITE_STATIC);
      }else{
        char *zCom = sqlite3VdbeDisplayComment(pVTab->db, pOp, pCur->zP4);
        sqlite3_result_text(ctx, zCom, -1, sqlite3_free);
      }
      break;
    case 6:
      sqlite3_result_int(ctx, pOp->p5);
      break;
  }
  return SQLITE_OK;
}

/*
** Return the rowid for the current row.  In this implementation, the
** rowid is the same as the output value.
*/
static int bytecodevtabRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor*)cur;
  *pRowid = pCur->iRowid;
  return SQLITE_OK;
}

/*







** Initialize a cursor to use a new


** to the first row of output.  This method is always called at least
** once prior to any call to bytecodevtabColumn() or bytecodevtabRowid() or 
** bytecodevtabEof().
*/
static int bytecodevtabFilter(
  sqlite3_vtab_cursor *pVtabCursor, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  bytecodevtab_cursor *pCur = (bytecodevtab_cursor *)pVtabCursor;
  bytecodevtab *pVTab = (bytecodevtab *)pVtabCursor->pVtab;
  int rc = SQLITE_OK;

  bytecodevtabCursorClear(pCur);
  pCur->iRowid = 0;
  pCur->iAddr = 0;
  assert( argc==1 );
  if( sqlite3_value_type(argv[0])==SQLITE_TEXT ){
    const char *zSql = (const char*)sqlite3_value_text(argv[0]);
    if( zSql==0 ){
      rc = SQLITE_NOMEM;
    }else{
      rc = sqlite3_prepare_v2(pVTab->db, zSql, -1, &pCur->pStmt, 0);
      pCur->needFinalize = 1;
    }
  }else{
    pCur->pStmt = (sqlite3_stmt*)sqlite3_value_pointer(argv[0],"stmt-pointer");
  }
  if( pCur->pStmt==0 ){
    pVTab->base.zErrMsg = sqlite3_mprintf(
       "argument to bytecode() is not a valid SQL statement"
    );
    rc = SQLITE_ERROR;
  }else{
    bytecodevtabNext(pVtabCursor);
  }
  return rc;
}

/*



** We must have a single stmt=? constraint that will be passed through
** into the xFilter method.  If there is no valid stmt=? constraint,
** then return an SQLITE_CONSTRAINT error.
*/
static int bytecodevtabBestIndex(
  sqlite3_vtab *tab,
  sqlite3_index_info *pIdxInfo
){
  int i;
  int rc = SQLITE_CONSTRAINT;
  pIdxInfo->estimatedCost = (double)100;
  pIdxInfo->estimatedRows = 100;
  for(i=0; i<pIdxInfo->nConstraint; i++){
    if( pIdxInfo->aConstraint[i].usable==0 ) continue;
    if( pIdxInfo->aConstraint[i].op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
    if( pIdxInfo->aConstraint[i].iColumn!=9 ) continue;
    rc = SQLITE_OK;
    pIdxInfo->aConstraintUsage[i].omit = 1;
    pIdxInfo->aConstraintUsage[i].argvIndex = 1;
    break;
  }
  return rc;
}

/*
** This following structure defines all the methods for the 
** virtual table.
*/
static sqlite3_module bytecodevtabModule = {
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  /* xRollbackTo */ 0,
  /* xShadowName */ 0
};


int sqlite3VdbeBytecodeVtabInit(sqlite3 *db){
  int rc;
  rc = sqlite3_create_module(db, "bytecodevtab", &bytecodevtabModule, 0);
  return rc;
}
#endif /* SQLITE_ENABLE_BYTECODE_VTAB */







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  /* xRollbackTo */ 0,
  /* xShadowName */ 0
};


int sqlite3VdbeBytecodeVtabInit(sqlite3 *db){
  int rc;
  rc = sqlite3_create_module(db, "bytecode", &bytecodevtabModule, 0);
  return rc;
}
#endif /* SQLITE_ENABLE_BYTECODE_VTAB */