我有一个上限集合，它是用 java 代码创建的:

this.collection = db.createCollection("stat", new BasicDBObject("capped", true).append("size", 200000000).append("max", 1000000));

现在在这个集合的统计中我们有:

/* 0 */
{
    "ns" : "myDatabase.stat",
    "count" : 12212,
    "size" : 2146416,
    "avgObjSize" : 175,
    "storageSize" : 200003584,
    "numExtents" : 1,
    "nindexes" : 4,
    "lastExtentSize" : 200003584,
    "paddingFactor" : 1,
    "systemFlags" : 1,
    "userFlags" : 0,
    "totalIndexSize" : 2272928,
    "indexSizes" : {
        "_id_" : 1259104,
        "downloaded_1" : 335216,
        "submitted_1" : 318864,
        "retries_1" : 359744
    },
    "capped" : true,
    "max" : 1000000,
    "ok" : 1
}

如果我尝试使用此代码在集合中插入文档:

BasicDBObject doc = new BasicDBObject().
        append("downloaded", new Date(0)).
        append("sessionId", sessionId).
        append("group", group);
collection.update(new BasicDBObject("_id", request.getUrl()), new BasicDBObject("$set", doc), true, false);

我发现了这个错误:

com.mongodb.WriteConcernException: { "serverUsed" : "/127.0.0.1:27017" , "lastOp" : { "$ts" : 0 , "$inc" : 0} , "connectionId" : 16420 , "err" : "failing update: objects in a capped ns cannot grow" , "code" : 10003 , "n" : 0 , "ok" : 1.0}
        at com.mongodb.CommandResult.getException(CommandResult.java:77)
        at com.mongodb.CommandResult.throwOnError(CommandResult.java:110)
        at com.mongodb.DBTCPConnector._checkWriteError(DBTCPConnector.java:102)
        at com.mongodb.DBTCPConnector.say(DBTCPConnector.java:142)
        at com.mongodb.DBTCPConnector.say(DBTCPConnector.java:115)
        at com.mongodb.DBApiLayer$MyCollection.update(DBApiLayer.java:327)
        at com.mongodb.DBCollection.update(DBCollection.java:178)
        at com.mongodb.DBCollection.update(DBCollection.java:209)
        at com.srg.hydra.monitoring.HydraStatistics.insert(HydraStatistics.java:63)
        at com.srg.hydra.HydraSite.onSubmit(HydraSite.java:91)
        at ru.decipher.site.AbstractSite.submit(AbstractSite.java:198)
        at com.srg.hydra.Eip.start(Eip.java:48)
        at com.srg.hydra.runner.DefaultHydraRunner.doCrawling(DefaultHydraRunner.java:180)
        at com.srg.hydra.runner.DefaultHydraRunner$1.run(DefaultHydraRunner.java:155)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
        at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:744)

我做错了什么？以及如何解决？ (排除 .drop() 这个集合并重新创建) 谢谢解答!

最佳答案

您不能更新上限集合中的文档。(如果您阅读了我的完整回答，可以找到解决方法)。我过去遇到过这个问题。请从下面的 MongoDB 文档中找到此问题的详细信息(和解决方案):

建议和限制

• You can only make in-place updates of documents. If the update operation causes the document to grow beyond their original size, the update operation will fail.

• If you plan to update documents in a capped collection, create an index so that these update operations do not require a table scan.

• If you update a document in a capped collection to a size smaller than its original size, and then a secondary resyncs from the primary, the secondary will replicate and allocate space based on the current smaller document size. If the primary then receives an update which increases the document back to its original size, the primary will accept the update but the secondary will fail with a failing update: objects in a capped ns cannot grow error message.

• To prevent this error, create your secondary from a snapshot of one of the other up-to-date members of the replica set. Follow our tutorial on filesystem snapshots to seed your new secondary.

• Seeding the secondary with a filesystem snapshot is the only way to guarantee the primary and secondary binary files are compatible. MMS Backup snapshots are insufficient in this situation since you need more than the content of the secondary to match the primary.

• You cannot delete documents from a capped collection. To remove all records from a capped collection, use the ‘emptycapped’ command. To remove the collection entirely, use the drop() method.

• You cannot shard a capped collection.

• Capped collections created after 2.2 have an _id field and an index on the _id field by default. Capped collections created before 2.2 do not have an index on the _id field by default. If you are using capped collections with replication prior to 2.2, you should explicitly create an index on the _id field.

关于java - 如果上限集合达到最大大小，为什么 MongoDB 不会删除旧文档？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25803479/