static int fts3EvalNearTest(Fts3Expr *pExpr, int *pRc){
  int res = 1;

  /* The following block runs if pExpr is the root of a NEAR query.
  ** For example, the query:
  **
  **         "w" NEAR "x" NEAR "y" NEAR "z"
  **
  ** which is represented in tree form as:
  **
  **                               |
  **                          +--NEAR--+      <-- root of NEAR query
  **                          |        |
  **                     +--NEAR--+   "z"
  **                     |        |
  **                +--NEAR--+   "y"
  **                |        |
  **               "w"      "x"
  **
  ** The right-hand child of a NEAR node is always a phrase. The 
  ** left-hand child may be either a phrase or a NEAR node. There are
  ** no exceptions to this - it's the way the parser in fts3_expr.c works.
  */
  if( *pRc==SQLITE_OK 
   && pExpr->eType==FTSQUERY_NEAR 
   && pExpr->bEof==0
   && (pExpr->pParent==0 || pExpr->pParent->eType!=FTSQUERY_NEAR)
  ){
    Fts3Expr *p; 
    int nTmp = 0;                 /* Bytes of temp space */
    char *aTmp;                   /* Temp space for PoslistNearMerge() */

    /* Allocate temporary working space. */
    for(p=pExpr; p->pLeft; p=p->pLeft){
      nTmp += p->pRight->pPhrase->doclist.nList;
    }
    nTmp += p->pPhrase->doclist.nList;
    if( nTmp==0 ){
      res = 0;
    }else{
      aTmp = sqlite3_malloc(nTmp*2);
      if( !aTmp ){
        *pRc = SQLITE_NOMEM;
        res = 0;
      }else{
        char *aPoslist = p->pPhrase->doclist.pList;
        int nToken = p->pPhrase->nToken;

        for(p=p->pParent;res && p && p->eType==FTSQUERY_NEAR; p=p->pParent){
          Fts3Phrase *pPhrase = p->pRight->pPhrase;
          int nNear = p->nNear;
          res = fts3EvalNearTrim(nNear, aTmp, &aPoslist, &nToken, pPhrase);
        }

        aPoslist = pExpr->pRight->pPhrase->doclist.pList;
        nToken = pExpr->pRight->pPhrase->nToken;
        for(p=pExpr->pLeft; p && res; p=p->pLeft){
          int nNear;
          Fts3Phrase *pPhrase;
          assert( p->pParent && p->pParent->pLeft==p );
          nNear = p->pParent->nNear;
          pPhrase = (
              p->eType==FTSQUERY_NEAR ? p->pRight->pPhrase : p->pPhrase
              );
          res = fts3EvalNearTrim(nNear, aTmp, &aPoslist, &nToken, pPhrase);
        }
      }

      sqlite3_free(aTmp);
    }
  }

  return res;
}
Unknown