Question

如何在Monger中使用find-maps时设置ReadPreference？ Monger文档仅指定monger.query的with-collection用法，如下所示

typedef struct {
  enum {
    TA,
    TB
  } _;
  union {
    struct {
      int a;
    };
    struct {
      float b;
    };
  };
} C;

C c = { ._ = TA, .a = 1 };

Answer 1

这样做的一种方法是在连接Mongo时设置读取首选项：

(mg/connect
  (mg/server-address "127.0.0.1" 27017)
  (mg/mongo-options {:read-preference (com.mongodb.ReadPreference/secondaryPreferred)}))

如果您正在考虑在Java API中使用此方法：https://mongodb.github.io/mongo-java-driver/3.4/javadoc/com/mongodb/DBCollection.html#setReadPreference-com.mongodb.ReadPreference-我找不到通过monger使用此方法的方法。但是，您可以使用自己的函数来利用此API：

(defn find-with-read-preference [db coll]
  (.find (doto
           (.getCollection db (name coll))
           (.setReadPreference (ReadPreference/secondaryPreferred)))))

(defn find-maps-with-read-preference
  ([^DB db ^String coll]
   (with-open [result (find-with-read-preference db coll)]
     (map (fn [x] (monger.conversion/from-db-object x true)) result))))

在Clojure MongoDb Driver Monger中设置ReadPreference

1 个答案: