Method FindJoinFilter

storage/connect/filter.cpp:537–726

/ Check that this filter is a good join filter. */ If so the opj block will be set accordingly. */ opj points to the join block, fprec to the filter block to which */ the rest of the chain must be linked in case of success. */ teq, tek and tk2 indicates the severity of the tests: */ tk2 == TRUE means both columns must be primary k

/*  thx == TRUE means at least one column must be a leading index key. */
/***********************************************************************/
bool FILTER::FindJoinFilter(POPJOIN opj, PFIL fprec, bool teq, bool tek,
                            bool tk2, bool tc2, bool tix, bool thx)
  {
  if (trace(1))
    htrc("FindJoinFilter: opj=%p fprec=%p tests=(%d,%d,%d,%d)\n",
                          opj, fprec, teq, tek, tk2, tc2);

  // Firstly check that this filter is an independent filter
  // meaning that it is the only one in its own group.
  if (Next && Next->Opc != OP_SEP)
    return (Opc < 0);

  // Keep only equi-joins and specific joins (Outer and Distinct)
  // Normally specific join operators come first because they have
  // been placed first by SortJoin.
  if (teq && Opc > OP_EQ)
    return FALSE;

  // We have a candidate for join filter, now check that it
  // fulfil the requirement about its operands, to point to
  // columns of respectively the two TDB's of that join.
  int    col1 = 0, col2 = 0;
  bool   key = tk2;
  bool   idx = FALSE, ihx = FALSE;
  PIXDEF pdx;

  for (int i = 0; i < 2; i++)
    if (GetArgType(i) == TYPE_COLBLK) {
      PCOL colp = (PCOL)Arg(i);

      if (tk2)
        key &= (colp->IsKey());
      else
        key |= (colp->IsKey());

      pdx = ((PTDBASE)colp->GetTo_Tdb())->GetColIndex(colp);
      idx |= (pdx && pdx->GetNparts() == 1);
      ihx |= (pdx != NULL);

      if      (colp->VerifyColumn(opj->GetTbx1()))
        col1 = i + 1;
      else if (colp->VerifyColumn(opj->GetTbx2()))
        col2 = i + 1;

    } else if (!tc2 && GetArgType(i) != TYPE_CONST) {
      PXOB xp = Arg(i);

      if      (xp->VerifyColumn(opj->GetTbx1()))
        col1 = i + 1;
      else if (xp->VerifyColumn(opj->GetTbx2()))
        col2 = i + 1;

    } else
      return (Opc < 0);

  if (col1 == 0 || col2 == 0)
    return (Opc < 0);