static int fts3EvalStart(Fts3Cursor *pCsr){
  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
  int rc = SQLITE_OK;
  int nToken = 0;
  int nOr = 0;

  /* Allocate a MultiSegReader for each token in the expression. */
  fts3EvalAllocateReaders(pCsr, pCsr->pExpr, &nToken, &nOr, &rc);

  /* Determine which, if any, tokens in the expression should be deferred. */
#ifndef SQLITE_DISABLE_FTS4_DEFERRED
  if( rc==SQLITE_OK && nToken>1 && pTab->bFts4 ){
    Fts3TokenAndCost *aTC;
    Fts3Expr **apOr;
    aTC = (Fts3TokenAndCost *)sqlite3_malloc(
        sizeof(Fts3TokenAndCost) * nToken
      + sizeof(Fts3Expr *) * nOr * 2
    );
    apOr = (Fts3Expr **)&aTC[nToken];

    if( !aTC ){
      rc = SQLITE_NOMEM;
    }else{
      int ii;
      Fts3TokenAndCost *pTC = aTC;
      Fts3Expr **ppOr = apOr;

      fts3EvalTokenCosts(pCsr, 0, pCsr->pExpr, &pTC, &ppOr, &rc);
      nToken = (int)(pTC-aTC);
      nOr = (int)(ppOr-apOr);

      if( rc==SQLITE_OK ){
        rc = fts3EvalSelectDeferred(pCsr, 0, aTC, nToken);
        for(ii=0; rc==SQLITE_OK && ii<nOr; ii++){
          rc = fts3EvalSelectDeferred(pCsr, apOr[ii], aTC, nToken);
        }
      }

      sqlite3_free(aTC);
    }
  }
#endif

  fts3EvalStartReaders(pCsr, pCsr->pExpr, &rc);
  return rc;
}
Unknown