static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
  Vdbe *v = 0;
  int iLimit = 0;
  int iOffset;
  int n;
  Expr *pLimit = p->pLimit;

  if( p->iLimit ) return;

  /* 
  ** "LIMIT -1" always shows all rows.  There is some
  ** controversy about what the correct behavior should be.
  ** The current implementation interprets "LIMIT 0" to mean
  ** no rows.
  */
  sqlite3ExprCacheClear(pParse);
  if( pLimit ){
    assert( pLimit->op==TK_LIMIT );
    assert( pLimit->pLeft!=0 );
    p->iLimit = iLimit = ++pParse->nMem;
    v = sqlite3GetVdbe(pParse);
    assert( v!=0 );
    if( sqlite3ExprIsInteger(pLimit->pLeft, &n) ){
      sqlite3VdbeAddOp2(v, OP_Integer, n, iLimit);
      VdbeComment((v, "LIMIT counter"));
      if( n==0 ){
        sqlite3VdbeGoto(v, iBreak);
      }else if( n>=0 && p->nSelectRow>sqlite3LogEst((u64)n) ){
        p->nSelectRow = sqlite3LogEst((u64)n);
        p->selFlags |= SF_FixedLimit;
      }
    }else{
      sqlite3ExprCode(pParse, pLimit->pLeft, iLimit);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit); VdbeCoverage(v);
      VdbeComment((v, "LIMIT counter"));
      sqlite3VdbeAddOp2(v, OP_IfNot, iLimit, iBreak); VdbeCoverage(v);
    }
    if( pLimit->pRight ){
      p->iOffset = iOffset = ++pParse->nMem;
      pParse->nMem++;   /* Allocate an extra register for limit+offset */
      sqlite3ExprCode(pParse, pLimit->pRight, iOffset);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset); VdbeCoverage(v);
      VdbeComment((v, "OFFSET counter"));
      sqlite3VdbeAddOp3(v, OP_OffsetLimit, iLimit, iOffset+1, iOffset);
      VdbeComment((v, "LIMIT+OFFSET"));
    }
  }
}
Unknown