SQLite

#define Deephemeralize(P) \
   if( ((P)->flags&MEM_Ephem)!=0 \
       && sqlite3VdbeMemMakeWriteable(P) ){ goto no_mem;}

/* Return true if the cursor was opened using the OP_OpenSorter opcode. */
#define isSorter(x) ((x)->pSorter!=0)













/*
** Allocate VdbeCursor number iCur.  Return a pointer to it.  Return NULL
** if we run out of memory.
*/
static VdbeCursor *allocateCursor(
  Vdbe *p,              /* The virtual machine */
  int iCur,             /* Index of the new VdbeCursor */

    assert( pc>=0 && pc<p->nOp );
    if( db->mallocFailed ) goto no_mem;
#ifdef VDBE_PROFILE
    start = sqlite3Hwtime();
#endif
    nVmStep++;
    pOp = &aOp[pc];
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
    if( p->pFrame==0 ) p->anExec[pc]++;
#endif

    /* Only allow tracing if SQLITE_DEBUG is defined.
    */
#ifdef SQLITE_DEBUG
    if( db->flags & SQLITE_VdbeTrace ){
      sqlite3VdbePrintOp(stdout, pc, pOp);
    }

  assert( pC->isOrdered );
  assert( pC->pCursor!=0 );
  oc = pOp->opcode;
  pC->nullRow = 0;
#ifdef SQLITE_DEBUG
  pC->seekOp = pOp->opcode;
#endif

  if( pC->isTable ){
    /* The input value in P3 might be of any type: integer, real, string,
    ** blob, or NULL.  But it needs to be an integer before we can do
    ** the seek, so convert it. */
    pIn3 = &aMem[pOp->p3];
    if( (pIn3->flags & (MEM_Int|MEM_Real|MEM_Str))==MEM_Str ){
      applyNumericAffinity(pIn3, 0);

      res = sqlite3BtreeEof(pC->pCursor);
    }
  }
  assert( pOp->p2>0 );
  VdbeBranchTaken(res!=0,2);
  if( res ){
    pc = pOp->p2 - 1;


  }
  break;
}

/* Opcode: Seek P1 P2 * * *
** Synopsis:  intkey=r[P2]
**

  assert( pC->isTable );
  assert( pC->pseudoTableReg==0 );
  pCrsr = pC->pCursor;
  assert( pCrsr!=0 );
  res = 0;
  iKey = pIn3->u.i;
  rc = sqlite3BtreeMovetoUnpacked(pCrsr, 0, iKey, 0, &res);

  pC->movetoTarget = iKey;  /* Used by OP_Delete */
  pC->nullRow = 0;
  pC->cacheStatus = CACHE_STALE;
  pC->deferredMoveto = 0;
  VdbeBranchTaken(res!=0,2);
  if( res!=0 ){
    pc = pOp->p2 - 1;


  }
  pC->seekResult = res;
  break;
}

/* Opcode: Sequence P1 P2 * * *
** Synopsis: r[P2]=cursor[P1].ctr++

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  pCrsr = pC->pCursor;
  res = 0;
  assert( pCrsr!=0 );
  rc = sqlite3BtreeLast(pCrsr, &res);


  pC->nullRow = (u8)res;
  pC->deferredMoveto = 0;
  pC->cacheStatus = CACHE_STALE;
#ifdef SQLITE_DEBUG
  pC->seekOp = OP_Last;
#endif
  if( pOp->p2>0 ){

  }else{
    pCrsr = pC->pCursor;
    assert( pCrsr );
    rc = sqlite3BtreeFirst(pCrsr, &res);
    pC->deferredMoveto = 0;
    pC->cacheStatus = CACHE_STALE;
  }

  pC->nullRow = (u8)res;
  assert( pOp->p2>0 && pOp->p2<p->nOp );
  VdbeBranchTaken(res!=0,2);
  if( res ){
    pc = pOp->p2 - 1;


  }
  break;
}

/* Opcode: Next P1 P2 P3 P4 P5
**
** Advance cursor P1 so that it points to the next key/data pair in its

       || pC->seekOp==OP_Last );

  rc = pOp->p4.xAdvance(pC->pCursor, &res);
next_tail:
  pC->cacheStatus = CACHE_STALE;
  VdbeBranchTaken(res==0,2);
  if( res==0 ){

    pC->nullRow = 0;
    pc = pOp->p2 - 1;
    p->aCounter[pOp->p5]++;
#ifdef SQLITE_TEST
    sqlite3_search_count++;
#endif
  }else{

    sqlite3VtabImportErrmsg(p, pVtab);
    if( rc==SQLITE_OK ){
      res = pModule->xEof(pVtabCursor);
    }
    VdbeBranchTaken(res!=0,2);
    if( res ){
      pc = pOp->p2 - 1;


    }

  }
  pCur->nullRow = 0;

  break;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

  if( rc==SQLITE_OK ){
    res = pModule->xEof(pCur->pVtabCursor);
  }
  VdbeBranchTaken(!res,2);
  if( !res ){
    /* If there is data, jump to P2 */
    pc = pOp->p2 - 1;

  }
  goto check_for_interrupt;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Opcode: VRename P1 * * P4 *

    sqlite3DebugPrintf("SQL-trace: %s\n", zTrace);
  }
#endif /* SQLITE_DEBUG */
#endif /* SQLITE_OMIT_TRACE */
  break;
}















/* Opcode: Noop * * * * *
**
** Do nothing.  This instruction is often useful as a jump
** destination.
*/
/*

/*
** A single VDBE is an opaque structure named "Vdbe".  Only routines
** in the source file sqliteVdbe.c are allowed to see the insides
** of this structure.
*/
typedef struct Vdbe Vdbe;


/*
** The names of the following types declared in vdbeInt.h are required
** for the VdbeOp definition.
*/
typedef struct Mem Mem;
typedef struct SubProgram SubProgram;

    FuncDef *pFunc;        /* Used when p4type is P4_FUNCDEF */
    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 *);
  } p4;
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
  char *zComment;          /* Comment to improve readability */
#endif
#ifdef VDBE_PROFILE
  u32 cnt;                 /* Number of times this instruction was executed */

struct VdbeOpList {
  u8 opcode;          /* What operation to perform */
  signed char p1;     /* First operand */
  signed char p2;     /* Second parameter (often the jump destination) */
  signed char p3;     /* Third parameter */
};
typedef struct VdbeOpList VdbeOpList;














/*
** Allowed values of VdbeOp.p4type
*/
#define P4_NOTUSED    0   /* The P4 parameter is not used */
#define P4_DYNAMIC  (-1)  /* Pointer to a string obtained from sqliteMalloc() */
#define P4_STATIC   (-2)  /* Pointer to a static string */
#define P4_COLLSEQ  (-4)  /* P4 is a pointer to a CollSeq structure */
#define P4_FUNCDEF  (-5)  /* P4 is a pointer to a FuncDef structure */
#define P4_KEYINFO  (-6)  /* P4 is a pointer to a KeyInfo structure */
#define P4_MEM      (-8)  /* P4 is a pointer to a Mem*    structure */
#define P4_TRANSIENT  0   /* P4 is a pointer to a transient string */
#define P4_VTAB     (-10) /* P4 is a pointer to an sqlite3_vtab structure */
#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() */


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

#else
# define VdbeCoverage(v)
# define VdbeCoverageIf(v,x)
# define VdbeCoverageAlwaysTaken(v)
# define VdbeCoverageNeverTaken(v)
# define VDBE_OFFSET_LINENO(x) 0
#endif

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
void sqlite3VdbeScanCounter(Vdbe*, int, int, int, i64, const char*);
#else
# define sqlite3VdbeScanCounter(a,b,c,d,e)
#endif

#endif

  Bool isTable:1;       /* True if a table requiring integer keys */
  Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
  Pgno pgnoRoot;        /* Root page of the open btree cursor */
  sqlite3_vtab_cursor *pVtabCursor;  /* The cursor for a virtual table */
  i64 seqCount;         /* Sequence counter */
  i64 movetoTarget;     /* Argument to the deferred sqlite3BtreeMoveto() */
  VdbeSorter *pSorter;  /* Sorter object for OP_SorterOpen cursors */


  /* Cached information about the header for the data record that the
  ** cursor is currently pointing to.  Only valid if cacheStatus matches
  ** Vdbe.cacheCtr.  Vdbe.cacheCtr will never take on the value of
  ** CACHE_STALE and so setting cacheStatus=CACHE_STALE guarantees that
  ** the cache is out of date.
  **

  Vdbe *pVdbe;       /* Attach the explanation to this Vdbe */
  StrAccum str;      /* The string being accumulated */
  int nIndent;       /* Number of elements in aIndent */
  u16 aIndent[100];  /* Levels of indentation */
  char zBase[100];   /* Initial space */
};


/* A bitfield type for use inside of structures.  Always follow with :N where
** N is the number of bits.
*/
typedef unsigned bft;  /* Bit Field Type */

typedef struct ScanCounter ScanCounter;
struct ScanCounter {
  int addrExplain;                /* OP_Explain for loop */
  int addrLoop;                   /* Address of "loops" counter */
  int addrVisit;                  /* Address of "rows visited" counter */
  i64 nEst;                       /* Estimated rows per loop */
  char *zName;                    /* Name of table or index */
};

/*
** An instance of the virtual machine.  This structure contains the complete
** state of the virtual machine.
**
** The "sqlite3_stmt" structure pointer that is returned by sqlite3_prepare()
** is really a pointer to an instance of this structure.

  VdbeFrame *pDelFrame;   /* List of frame objects to free on VM reset */
  int nFrame;             /* Number of frames in pFrame list */
  u32 expmask;            /* Binding to these vars invalidates VM */
  SubProgram *pProgram;   /* Linked list of all sub-programs used by VM */
  int nOnceFlag;          /* Size of array aOnceFlag[] */
  u8 *aOnceFlag;          /* Flags for OP_Once */
  AuxData *pAuxData;      /* Linked list of auxdata allocations */
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  i64 *anExec;            /* Number of times each op has been executed */
  int nScan;              /* Entries in aScan[] */
  ScanCounter *aScan;     /* Scan definitions for sqlite3_stmt_scanstatus() */
#endif
};

/*
** The following are allowed values for Vdbe.magic
*/
#define VDBE_MAGIC_INIT     0x26bceaa5    /* Building a VDBE program */
#define VDBE_MAGIC_RUN      0xbdf20da3    /* VDBE is ready to execute */

  }
#endif
  v = pVdbe->aCounter[op];
  if( resetFlag ) pVdbe->aCounter[op] = 0;
  return (int)v;
}

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
/*
** Return status data for a single loop within query pStmt.
*/
int sqlite3_stmt_scanstatus(
  sqlite3_stmt *pStmt,
  int idx,                        /* Index of loop to report on */
  sqlite3_int64 *pnLoop,          /* OUT: Number of times loop was run */
  sqlite3_int64 *pnVisit,         /* OUT: Number of rows visited (all loops) */
  sqlite3_int64 *pnEst,           /* OUT: Number of rows estimated (per loop) */
  const char **pzName,            /* OUT: Object name (table or index) */
  const char **pzExplain          /* OUT: EQP string */
){
  Vdbe *p = (Vdbe*)pStmt;
  ScanCounter *pScan;
  if( idx<0 || idx>=p->nScan ) return 1;
  pScan = &p->aScan[idx];
  if( pnLoop ) *pnLoop = p->anExec[pScan->addrLoop];
  if( pnVisit ) *pnVisit = p->anExec[pScan->addrVisit];
  if( pnEst ) *pnEst = pScan->nEst;
  if( *pzName ) *pzName = pScan->zName;
  if( *pzExplain ){
    if( pScan->addrExplain ){
      *pzExplain = p->aOp[ pScan->addrExplain ].p4.z;
    }else{
      *pzExplain = 0;
    }
  }
  return 0;
}

/*
** Zero all counters associated with the sqlite3_stmt_scanstatus() data.
*/
void sqlite3_stmt_scanstatus_reset(sqlite3_stmt *pStmt){
  Vdbe *p = (Vdbe*)pStmt;

  memset(p->anExec, 0, p->nOp * sizeof(i64));


}

#endif /* SQLITE_ENABLE_STMT_SCANSTATUS */

      }
#endif
    }
    p->nOp += nOp;
  }
  return addr;
}

#if defined(SQLITE_ENABLE_STMT_SCANSTATUS)
/*
** Add an entry to the array of counters managed by sqlite3_stmt_scanstatus().
*/
void sqlite3VdbeScanCounter(
  Vdbe *p,                        /* VM to add scanstatus() to */
  int addrExplain,                /* Address of OP_Explain (or 0) */
  int addrLoop,                   /* Address of loop counter */ 
  int addrVisit,                  /* Address of rows visited counter */
  i64 nEst,                       /* Estimated number of rows */
  const char *zName               /* Name of table or index being scanned */
){
  int nByte = (p->nScan+1) * sizeof(ScanCounter);
  ScanCounter *aNew;
  aNew = (ScanCounter*)sqlite3DbRealloc(p->db, p->aScan, nByte);
  if( aNew ){
    ScanCounter *pNew = &aNew[p->nScan++];
    pNew->addrExplain = addrExplain;
    pNew->addrLoop = addrLoop;
    pNew->addrVisit = addrVisit;
    pNew->nEst = nEst;
    pNew->zName = sqlite3DbStrDup(p->db, zName);
    p->aScan = aNew;
  }
}
#endif


/*
** Change the value of the P1 operand for a specific instruction.
** This routine is useful when a large program is loaded from a
** static array using sqlite3VdbeAddOpList but we want to make a
** few minor changes to the program.
*/

/*
** Delete a P4 value if necessary.
*/
static void freeP4(sqlite3 *db, int p4type, void *p4){
  if( p4 ){
    assert( db );
    switch( p4type ){

      case P4_REAL:
      case P4_INT64:
      case P4_DYNAMIC:
      case P4_INTARRAY: {
        sqlite3DbFree(db, p4);
        break;
      }

    pOp->p4.p = (void*)zP4;
    pOp->p4type = P4_KEYINFO;
  }else if( n==P4_VTAB ){
    pOp->p4.p = (void*)zP4;
    pOp->p4type = P4_VTAB;
    sqlite3VtabLock((VTable *)zP4);
    assert( ((VTable *)zP4)->db==p->db );







  }else if( n<0 ){
    pOp->p4.p = (void*)zP4;
    pOp->p4type = (signed char)n;
  }else{
    if( n==0 ) n = sqlite3Strlen30(zP4);
    pOp->p4.z = sqlite3DbStrNDup(p->db, zP4, n);
    pOp->p4type = P4_DYNAMIC;

      sqlite3_snprintf(nTemp, zTemp, "program");
      break;
    }
    case P4_ADVANCE: {
      zTemp[0] = 0;
      break;
    }




    default: {
      zP4 = pOp->p4.z;
      if( zP4==0 ){
        zP4 = zTemp;
        zTemp[0] = 0;
      }
    }

    p->aOnceFlag = allocSpace(p->aOnceFlag, nOnce, &zCsr, zEnd, &nByte);
    if( nByte ){
      p->pFree = sqlite3DbMallocZero(db, nByte);
    }
    zCsr = p->pFree;
    zEnd = &zCsr[nByte];
  }while( nByte && !db->mallocFailed );

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
    p->anExec = (i64*)sqlite3DbMallocZero(db, p->nOp*sizeof(i64));
#endif

  p->nCursor = nCursor;
  p->nOnceFlag = nOnce;
  if( p->aVar ){
    p->nVar = (ynVar)nVar;
    for(n=0; n<nVar; n++){
      p->aVar[n].flags = MEM_Null;

    sqlite3DbFree(db, pSub);
  }
  for(i=p->nzVar-1; i>=0; i--) sqlite3DbFree(db, p->azVar[i]);
  vdbeFreeOpArray(db, p->aOp, p->nOp);
  sqlite3DbFree(db, p->aColName);
  sqlite3DbFree(db, p->zSql);
  sqlite3DbFree(db, p->pFree);
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  sqlite3DbFree(db, p->anExec);
  for(i=0; i<p->nScan; i++){
    sqlite3DbFree(db, p->aScan[i].zName);
  }
  sqlite3DbFree(db, p->aScan);
#endif
}

/*
** Delete an entire VDBE.
*/
void sqlite3VdbeDelete(Vdbe *p){
  sqlite3 *db;

      }
    }
  }
  *pzAff = zAff;
  return regBase;
}

#ifndef SQLITE_OMIT_EXPLAIN
/*
** This routine is a helper for explainIndexRange() below
**
** pStr holds the text of an expression that we are building up one term
** at a time.  This routine adds a new term to the end of the expression.
** Terms are separated by AND so add the "AND" text for second and subsequent
** terms only.

/*
** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
** command. If the query being compiled is an EXPLAIN QUERY PLAN, a single
** record is added to the output to describe the table scan strategy in 
** pLevel.
*/
static int explainOneScan(
  Parse *pParse,                  /* Parse context */
  SrcList *pTabList,              /* Table list this loop refers to */
  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
  int iLevel,                     /* Value for "level" column of output */
  int iFrom,                      /* Value for "from" column of output */
  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
){
  int ret = 0;
#ifndef SQLITE_DEBUG
  if( pParse->explain==2 )
#endif
  {

    struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
    Vdbe *v = pParse->pVdbe;      /* VM being constructed */
    sqlite3 *db = pParse->db;     /* Database handle */

    int iId = pParse->iSelectId;  /* Select id (left-most output column) */



    int isSearch;                 /* True for a SEARCH. False for SCAN. */
    WhereLoop *pLoop;             /* The controlling WhereLoop object */
    u32 flags;                    /* Flags that describe this loop */
    char *zMsg;                   /* Text to add to EQP output */
    StrAccum str;                 /* EQP output string */
    char zBuf[100];               /* Initial space for EQP output string */




    pLoop = pLevel->pWLoop;
    flags = pLoop->wsFlags;
    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) 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, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
    str.db = db;
    sqlite3StrAccumAppendAll(&str, isSearch ? "SEARCH" : "SCAN");
    if( pItem->pSelect ){



      sqlite3XPrintf(&str, 0, " SUBQUERY %d", pItem->iSelectId);

    }else{
      sqlite3XPrintf(&str, 0, " TABLE %s", pItem->zName);
    }

    if( pItem->zAlias ){
      sqlite3XPrintf(&str, 0, " AS %s", pItem->zAlias);
    }

    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
      sqlite3XPrintf(&str, 0, " VIRTUAL TABLE INDEX %d:%s",
                  pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
    }
#endif

#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
    if( pLoop->nOut>=10 ){
      sqlite3XPrintf(&str, 0, " (~%llu rows)", sqlite3LogEstToInt(pLoop->nOut));
    }else{
      sqlite3StrAccumAppend(&str, " (~1 row)", 9);
    }
#endif
    zMsg = sqlite3StrAccumFinish(&str);
    ret = sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg,P4_DYNAMIC);
  }
  return ret;





}
#else
# define explainOneScan(u,v,w,x,y,z) 0
#endif /* SQLITE_OMIT_EXPLAIN */


#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
static void addScanStatus(
  Vdbe *v, 
  SrcList *pSrclist,
  WhereLevel *pLvl,
  int addrExplain
){
  const char *zObj = 0;
  i64 nEst = 1;
  WhereLoop *pLoop = pLvl->pWLoop;
  if( (pLoop->wsFlags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
    zObj = pLoop->u.btree.pIndex->zName;
  }else{
    zObj = pSrclist->a[pLvl->iFrom].zName;
  }
  if( pLoop->nOut>=10 ){
    nEst = sqlite3LogEstToInt(pLoop->nOut);
  }
  sqlite3VdbeScanCounter(
      v, addrExplain, pLvl->addrBody, pLvl->addrVisit, nEst, zObj
  );
}
#else
# define addScanStatus(a, b, c, d)
#endif



/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
static Bitmask codeOneLoopStart(

        /* Loop through table entries that match term pOrTerm. */
        WHERETRACE(0xffff, ("Subplan for OR-clause:\n"));
        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
                                      wctrlFlags, iCovCur);
        assert( pSubWInfo || pParse->nErr || db->mallocFailed );
        if( pSubWInfo ){
          WhereLoop *pSubLoop;
          int addrExplain = explainOneScan(



              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
          );
          addScanStatus(v, pOrTab, &pSubWInfo->a[0], addrExplain);



          /* This is the sub-WHERE clause body.  First skip over
          ** duplicate rows from prior sub-WHERE clauses, and record the
          ** rowid (or PRIMARY KEY) for the current row so that the same
          ** row will be skipped in subsequent sub-WHERE clauses.
          */
          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){

      pLevel->p1 = iCur;
      pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
      VdbeCoverageIf(v, bRev==0);
      VdbeCoverageIf(v, bRev!=0);
      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
    }
  }

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  pLevel->addrVisit = sqlite3VdbeCurrentAddr(v);
#endif

  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  */
  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    Expr *pE;
    testcase( pTerm->wtFlags & TERM_VIRTUAL );

  /* Generate the code to do the search.  Each iteration of the for
  ** loop below generates code for a single nested loop of the VM
  ** program.
  */
  notReady = ~(Bitmask)0;
  for(ii=0; ii<nTabList; ii++){
    int addrExplain;
    int wsFlags;
    pLevel = &pWInfo->a[ii];
    wsFlags = pLevel->pWLoop->wsFlags;
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
    if( (pLevel->pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 ){
      constructAutomaticIndex(pParse, &pWInfo->sWC,
                &pTabList->a[pLevel->iFrom], notReady, pLevel);
      if( db->mallocFailed ) goto whereBeginError;
    }
#endif
    addrExplain = explainOneScan(
        pParse, pTabList, pLevel, ii, pLevel->iFrom, wctrlFlags
    );
    pLevel->addrBody = sqlite3VdbeCurrentAddr(v);
    notReady = codeOneLoopStart(pWInfo, ii, notReady);
    pWInfo->iContinue = pLevel->addrCont;
    if( (wsFlags&WHERE_MULTI_OR)==0 && (wctrlFlags&WHERE_ONETABLE_ONLY)==0 ){
      addScanStatus(v, pTabList, pLevel, addrExplain);
    }
  }

  /* Done. */
  VdbeModuleComment((v, "Begin WHERE-core"));
  return pWInfo;

  /* Jump here if malloc fails */

        u8 eEndLoopOp;         /* IN Loop terminator. OP_Next or OP_Prev */
      } *aInLoop;           /* Information about each nested IN operator */
    } in;                 /* Used when pWLoop->wsFlags&WHERE_IN_ABLE */
    Index *pCovidx;       /* Possible covering index for WHERE_MULTI_OR */
  } u;
  struct WhereLoop *pWLoop;  /* The selected WhereLoop object */
  Bitmask notReady;          /* FROM entries not usable at this level */
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  int addrVisit;        /* Address at which row is visited */
#endif
};

/*
** Each instance of this object represents an algorithm for evaluating one
** term of a join.  Every term of the FROM clause will have at least
** one corresponding WhereLoop object (unless INDEXED BY constraints
** prevent a query solution - which is an error) and many terms of the

  zExplain {SEARCH TABLE x1 USING COVERING INDEX x1j (j=?)}
}

do_execsql_test 2.4.1 {
  SELECT * FROM x1 WHERE j<'two'
} {4 four 1 one 3 three}
do_scanstatus_test 2.4.2 {
  nLoop 1 nVisit 3 nEst 262144 zName x1j 
  zExplain {SEARCH TABLE x1 USING COVERING INDEX x1j (j<?)}
}

do_execsql_test 2.5.1 {
  SELECT * FROM x1 WHERE j>='two'
} {2 two}
do_scanstatus_test 2.5.2 {

  zExplain {SEARCH TABLE x2 USING INDEX x2j (j>? AND j<?)}
}

do_execsql_test 2.8.1 {
  SELECT * FROM x2 WHERE i=1 AND j='two'
}
do_scanstatus_test 2.8.2 {
  nLoop 1 nVisit 0 nEst 8 zName x2ij 
  zExplain {SEARCH TABLE x2 USING INDEX x2ij (i=? AND j=?)}
}

do_execsql_test 2.9.1 {
  SELECT * FROM x2 WHERE i=5 AND j='two'
}
do_scanstatus_test 2.9.2 {
  nLoop 1 nVisit 0 nEst 8 zName x2ij 
  zExplain {SEARCH TABLE x2 USING INDEX x2ij (i=? AND j=?)}
}

do_execsql_test 2.10.1 {
  SELECT * FROM x2 WHERE i=3 AND j='three'
} {3 three {3 three}}
do_scanstatus_test 2.10.2 {
  nLoop 1 nVisit 1 nEst 8 zName x2ij 
  zExplain {SEARCH TABLE x2 USING INDEX x2ij (i=? AND j=?)}
}

#-------------------------------------------------------------------------
# Try with queries that use the OR optimization.
#
do_execsql_test 3.1 {
  CREATE TABLE a1(a, b, c, d);
  CREATE INDEX a1a ON a1(a);
  CREATE INDEX a1bc ON a1(b, c);

  WITH d(x) AS (SELECT 1 UNION ALL SELECT x+1 AS n FROM d WHERE n<=100)
  INSERT INTO a1 SELECT x, x, x, x FROM d;
}

do_execsql_test 3.2.1 {
  SELECT d FROM a1 WHERE (a=4 OR b=13)
} {4 13}
do_scanstatus_test 3.2.2 {
  nLoop 1 nVisit 1 nEst 10 zName a1a 
  zExplain {SEARCH TABLE a1 USING INDEX a1a (a=?)}
  nLoop 1 nVisit 1 nEst 10 zName a1bc 
  zExplain {SEARCH TABLE a1 USING INDEX a1bc (b=?)}
}

do_execsql_test 3.2.1 {
  SELECT count(*) FROM a1 WHERE (a BETWEEN 4 AND 12) OR (b BETWEEN 40 AND 60)
} {30}
do_scanstatus_test 3.2.2 {
  nLoop 1 nVisit 9 nEst 16384 zName a1a 
  zExplain {SEARCH TABLE a1 USING INDEX a1a (a>? AND a<?)}
  nLoop 1 nVisit 21 nEst 16384 zName a1bc
  zExplain {SEARCH TABLE a1 USING INDEX a1bc (b>? AND b<?)}
}

do_execsql_test 3.3.1 {
  SELECT count(*) FROM a1 AS x, a1 AS y 
  WHERE (x.a BETWEEN 4 AND 12) AND (y.b BETWEEN 1 AND 10)
} {90}
do_scanstatus_test 3.2.2 {
  nLoop 1 nVisit 10 nEst 16384 zName a1bc 
  zExplain {SEARCH TABLE a1 AS y USING COVERING INDEX a1bc (b>? AND b<?)}
  nLoop 10 nVisit 90 nEst 16384 zName a1a
  zExplain {SEARCH TABLE a1 AS x USING COVERING INDEX a1a (a>? AND a<?)}
}

do_execsql_test 3.4.1 {
  SELECT count(*) FROM a1 WHERE a IN (1, 5, 10, 15);
} {4}
do_scanstatus_test 3.4.2 {
  nLoop 1 nVisit 4 nEst 40 zName a1a 
  zExplain {SEARCH TABLE a1 USING COVERING INDEX a1a (a=?)}
}

do_execsql_test 3.4.1 {
  SELECT count(*) FROM a1 WHERE rowid IN (1, 5, 10, 15);
} {4}
do_scanstatus_test 3.4.2 {
  nLoop 1 nVisit 4 nEst 4 zName a1
  zExplain {SEARCH TABLE a1 USING INTEGER PRIMARY KEY (rowid=?)}
}

finish_test