Question

我在ANSI C代码中使用mongoc库。我是mongoc API的新手，我在创建查询时遇到了问题。下面的代码抛出断言src / bson / bcon.c：807：bcon_append_ctx_va：断言`ctx-＆gt; n！= 0'失败。有人可以帮忙吗？

bool is_point_near_road(LOCATION_ITEM* item)
  {
  bson_error_t error;
  const bson_t *doc;
  char *str;
  query = BCON_NEW ("road_segment:", "{",
                  "$near:", "{",
                    "$geometry:", "{",
                      "type:", "Point", "coordinates:", "[",BCON_DOUBLE(27.9478454), ",", BCON_DOUBLE(65.6503487), "]",
                      "}", "$maxDistance:", BCON_INT32(500),
                    "}",
                  "}",
                 );
  cursor = mongoc_collection_find(collection_query, MONGOC_QUERY_NONE, 0, 0, 0, query, NULL, NULL);
  if (cursor == NULL)
    {
    printf ("Cursor is NULL");
    }
while (mongoc_cursor_more (cursor) && mongoc_cursor_next (cursor, &doc)) {
  str = bson_as_json (doc, NULL);
  printf ("STR: %s\n", str);
  bson_free (str);
}
if (mongoc_cursor_error (cursor, &error)) {
  fprintf (stderr, "An error occurred: %s\n", error.message);
}
mongoc_cursor_destroy (cursor);
bson_destroy (query);
return true;
}

Answer 1

我不明白你的错误，但我注意到你的查询至少有一个问题，就是“：”。

我猜你是从一个使用mongo客户端的例子开始的（我们在附近写了$ :)。对于BCON_NEW，不需要“：”。

我刚写了一个类似于你的查询，但它确实有用。尝试从查询中删除：

另外，不要在坐标上添加“，”，只需将它们添加到数组中即可。

最后，我使用mongoc_collection_find_with_opts

===========

query = BCON_NEW ("road_segment", "{",
    "$near", "{",
        "$geometry", "{",
            "type", "Point", 
            "coordinates", "[",
                BCON_DOUBLE(27.9478454), 
                BCON_DOUBLE(65.6503487), 
            "]",
        "}",
        "$maxDistance", BCON_INT32(500),
    "}",
"}");

在mongoc库中断言失败

1 个答案: