objectid

问题 I know how the _id column contains a representation of timestamp when the document has been inserted into the collection. here is an online utility to convert it to timestamp: http://steveridout.github.io/mongo-object-time/ What I'm wondering is if the object id string itself is guaranteed maintain the ascending order or not? i.e. does this comparison always return true? "newest object id" > "second newest object id" 回答1: No, there is no guarantee whatsoever. From the official documentation:

问题 I came across this ruby object_id allocation question sometime back and then read this awesome article which talks about VALUE and explains why object_id of true, nil and false the way they are. I have been toying with ruby2.0 object_id when I found the apparent change that has been made regarding object_id of true and nil. forbidden:~$ ruby -v ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-linux] forbidden:~$ forbidden:~$ irb irb(main):001:0> true.object_id => 20 irb(main):002:0> false

问题 I have a very open-ended API that allows the frontend to query the backend with more-or-less arbitrary mongo queries. I'm having problems with _ids being stored as ObjectIds but passed around as hex strings. If the frontend gives me some complicated mongo query, I don't want to have to implement logic to comb through all the crazy mongo query operators to replace string _ids with ObjectIds. Beyond that, objects in the system have user-defined schemas, and so there are cases where the backend

问题 So I'm creating a script where I"m linking a database that is in another server. Using OBJECT_ID I want to check whether a table exists in the external linked database like so: IF OBJECT_ID('[10.0.48.139].[DBNAME].[dbo].tblRating', 'U') IS NOT NULL BEGIN SET @Sql = N' INSERT INTO tblRating ( fldSubDivisionID , fldClientName , fldAddress , fldCountryID , fldComments , fldCreatedDate , fldCreatedBy , fldModifiedDate , fldModifiedBy ) SELECT * FROM ' + @SourceDB + '.tblRating'; EXECUTE sp

问题 I use Parse.com for backend, I've two views : InboxView (where I receive images from friends), and ChatView. When I send images, I send images with recipientIds of user (that can be multiple users) in "Messages" class (parse). I receive images in my InboxView, I can see in cell for row the name of the friend that send images. I would like that when I select a row (username who sends me image) that stores the PFUser objectId of the user who sends me the image, and not all of the recipientIds.

问题 I need to insert a document into a collection, which has an ObjectId and a BinData value. Therefore I don't know how to insert it. With this code I get the error TypeError: Cannot read property 'ObjectId' of undefined . server/fixtures.js var ObjectId = Mongo.ObjectID; var chunk = { "_id" : ObjectId("57a9be3c89c1e4b50c574e3a"), "files_id": ObjectId("5113b0062be53b231f9dbc11"), "n" : 0, "data" : BinData(0, "/9j/4AAQSkZJRgA...and...so...on../2Q==") }; db.mediafiles.chunks.insert(chunk); Update

问题 I would like to be able to get the same ID that is being used in Java heap dumps (created via jmap or JMX, etc). This is to be able to identify the live object at the still running application versus an older memory snapshot (the heap dump) of the same app. I have already tested a little and it is obvioulsy not the hashCode, neither the JDI unique ID (which you can see in your debuggers). From checking the code in the sun.jvm.hotspot.utilities I assume it is the objects address in memory. But

问题 I'm using Meteor and have a question about overriding the default behavior of what type Meteor uses for User ID's. I would like users to be uniquely identified by a _id field of type ObjectId instead of whatever type Meteor defaults to (string?). Is there something like a configuration parameter somewhere I can set in order to have this be the case? 回答1: Short answer: You cannot use Objectd for the _id property of the users collection. Long answer: This has been posted as a bug report at

问题 When I type this into my consol, it works: db.posts.find({"_id": {$lt:ObjectId("55732dccf58c555b6d3f1c5a")}}).limit(5).sort({"_id":-1}) When I use mongotemplate, it doesn't work and returns a blank array: @RequestMapping(value="/next", method=RequestMethod.GET) public List getNextPost(@RequestParam String next) { Query query = new Query(); query.addCriteria(Criteria.where("_id").lt("55732dccf58c555b6d3f1c5a")); List<Posts> posts = template.find(query, Posts.class); return posts; } I tried it

问题 I have data writing to a mongoDB database with issues using integration tests and the Grails scaffolding. When trying to select a domain instance from the 'list' type page, I get the error "[domain name] not found with id null". I am sure it is because of the Grails url [controller]/[action]/[id]. This id is a string and needs to be converted to an ObjectId for Grails queries. Is there a way to do this so that it affects a specified domain or even better yet, all of the domains at once? I