I'm building a chatroom application, and I want to keep track of which users are currently in the chatroom. However, I can't just store this array of users (or maybe a list would be better) in a field in one of my records in the Chatroom table.
Obviously one of the SQL data types is not an array, which leads me to this issue: what is the best way to fake/mock array functionality in a SQL database?
It seems there are 3 options:
1: Store the list/array of users as a string separated by commas, and just do some parsing when I want to get it back to an array
2: Since the max amount of users is allowed to be 10, just have 10 extra fields on each Chatroom record representing the users who are currently there
3: Have a new table Userchats, which has two fields, a reference to the chatroom, and a user name
I dunno, which is the best? I'm also open to other options. I'm also using Rails, which seems irrelevant here, but may be of interest.
Option 3 is the best. This is how you do it, in a relational schema. It is also the most flexible and future-proof option.
It can grow easier in width (extra columns say, a date joined, a channel status, a timestamp last talked) and length (extra rows when you decide there now can be 15 users in a room instead of 10).
The proper way to do this is to add an extra table representing an instance of a user being in a chatroom. In most cases, this is probably what you will want to do, since it gives you more flexibility in the types of queries you can do (for instance: list all chatrooms a particular user is in, find the average number of people in each chatroom, etc.) You would just need to add a new table - something like chat_room_users, with a chat_room_id, and a user_id.
If you're deadset on not adding an extra table, then Rails (or more specifically ActiveRecord), does have some functionality to store data structures like arrays in a SQL column. Just set up your column as a string or text type in a Rails migration, and add:
serialize :users
You can then use this column as a normal Ruby array / object, and ActiveRecord will automatically serialize / deserialize this object as you work with it. Keep in mind that's there are a lot of tradeoffs with this approach - you will never be able to query what users are in a particular room using SQL and will instead need to pull all data down to Ruby before working with it.
Related
I have run into a little roadblock in regards to joining mantle entities. I would like to have a single depicting fields from two mantle entities, but am unsuccessful in joining them. Specifically, I have linked a list of party relationships (as contacts) to a single partyId (vendor), with the goal to make a vendor contacts page. However I am unable to link that form-list with the PartyContactMech and ContactMech entities (in order to display email and phone number in the same form-list). More generally, my question is how can one map lists to each other the same way one can map a list to a single object (using entity-find-one and value-field does not work when tried with entity-find)?
There is no need to make a view-entity (join entities) to do that. Simply do a query on the PartyRelationship entity in the main 'actions' part of your screen specifying the toParty (vendor). Then in your Form-List, use 'row-actions' to query the PartyContactMech and so on for each fromPartyId (contact) entry that the previous query returned. Also have a look at the PartyViewEntities file in Mantle USL. There are some helpful view-enties already defined for you there such as PartyToAndRelationship, PartyFromAndRelationship etc. Also note that entity-find-one returns a single "map" (value-field) as it queries on the PK. Whereas entity-find returns a list of maps (list). They are separate query types. If I understand your question correctly.
I want make the program more simple, so I use table's field name as name in input html,
And then I can save some time for mapping input name to database field name
But, are there security risks if user know my field name?
(Suppose SQL injection have handled in the server program)
Update 1:
I am not going to around the field name validation
I just don't want to do something like this
$uid=$_POST['user_id'];
$ufname=$_POST['user_first_name'];
$ulname=$_POST['user_last_name'];
If I do this
$user_id=$_POST['user_id'];
$user_first_name=$_POST['user_first_name'];
$user_first_name=$_POST['user_last_name'];
I can save coding time, and don't need to think two names for one data, and reduce bug.
and I can also do something like this to save more time as I just type the name once.
$validField=array("user_id","user_first_name","user_last_name");
foreach ($validField as $field) {
$orm[$field]=$field;
}
This can also valid the field name
so I think that hacks are no way to get my unpublished fields
I can save some time for mapping input name to database field name.
If you save time mapping input names to database field names, you would need to spend a roughly equivalent time validating that the field names are, in fact, among the fields that the users can access in your database. There is no way around this validation, because otherwise your DB is exposed to hacks that try and get your unpublished fields, such as IDs and hashes. This is pretty bad, so you would need to build that validation layer.
On the other hand, if you do a mapping from meaningless IDs to meaningful, then you do not need validation, because it is your program that produced the meaningful IDs. Essentially, the validation step is built into the process.
it might be possible I'm searching for the wrong keywords, but so far I couldn't find anything useful.
My problem is quite simple: At the moment I get a list of individual Ids through a report parameter, I pass them to a procedure and show the results.
The new request is like this: Instead of showing the list for all individuals at once, there should be a list for each individual id.
Since I'm quite a beginner in srss, I thought the easiest approach would be the best: Create a subreport, copy the shown list, and create a subreport per individual id.
The amount of this IDs is dynamic, so I have to create a dynamic amount of subreports.
Funny enought, this doesnt seem to be possible. This http://forums.asp.net/t/1397645.aspx url doesnt show exactly the problem, but it shows the limit of the subreports.
I even ran trough the whole msdn pages starting http://technet.microsoft.com/en-us/library/dd220581.aspx but I couldnt find anything there.
So is there a possibility, to create a loop like:
For each Individual ID in Individual IDs, create a subreport and pass ONE ID to this?
Or is there another approach I should use to make this work?
I tried to create a 'Fake'-Dataset with no sql query but just for iterating the id list, but it seems the dataset needs a data-source...
As usual, thanks so far for all answers!
Matthias Müller
Or is there another approach I should use to make this work?
You didn't provide much detail about what sort of information needs to be included in the subreport, but assuming it's a small amount of data (say, showing a personnel record), and not a huge amount (such as a persons sales for the last year), a List might be the way to go.
I tried to create a 'Fake'-Dataset with no sql query but just for iterating the id list, but it seems the dataset needs a data-source...
All datasets require a data source, though if you're merely hard-coding some fake return data, any data source will do, even a local SQL instance with nothing in it.
I would like to join the user object and project permission object to see how many users have been assigned to a project, for audit purpose. I don't see a common field with common values (email address or first name/last name) between these objects. I used Excel plugin to retrieve two separate data sheet and unable to map them. Any thoughts on this on how to do this?
You're probably seeing something similar to the following when you query on ProjectPermissions:
In this situation, the default User object selected from the "Columns" picker in the query dialog, gives you the User's DisplayName, which doesn't unambiguously map to a Rally UserID.
Note, however, that you can add dot-notation sub-fields of Objects manually by typing them into the Columns field. In the following example, I've included User.Username and User.LastLoginDate as additional fields I want to show on the Permissions report:
Of course, you could also just include User.Username, and run a second query on the User object with all fields selected, and do a join in Excel.
One note of caution - if you have many users (say 1,000), and a lot of projects, (say 1,000, which is not uncommon in large Rally subscriptions), querying directly against the ProjectPermissions endpoint can rapidly result in total results that number on the order of 10^6. This will probably time out in an Excel query.
The Rally User Management: User Permissions Summary script works around this by querying Permissions in a loop on a user-by-user basis. It's slow, but it returns results without timeouts. Certainly not as convenient as Excel either - you need to install Ruby 1.9.2+ and the rally_api gem to get it working.
I have been experimenting with Redis, and I really like the scalability that it brings to the table. However, I'm wondering how to handle changes to data structures for a system that's already in production.
For example, let me say that I am collecting information about a user, and I use the user_id as a key, and dumping the other data about the user as comma separated values.
user_id: name, email, etc.
Now, say after about 100,000 records, I realise that I needed to query by email - how would I now take a snapshot of the existing data and create a new index for it?
Using csv is not a great idea if you want to support changes. You need to use a serializer that handles missing/new values if everything is in one key, or you can use a redis hash, which gives you named subkeys. Either way you can add/remove fields with the only requirement being that your code knows what to do if it reads a record without the new value.
To allow lookup by email you need to add an index - basically a key (or list) for each email with the user id as the value. You will need to populate this index by getting all keys once, then making sure you update it when emails change.
You could iterate over all keys and store them with a different id, but that is probably more trouble than it is worth.
From my understanding of Redis, this would require something which Redis is not designed to do. You would have to loop though all your records (using keys *) and then change the order of the data and make a new key. I, personally, would recommend using a list instead of a comma separated string. In a list, you can reorder it from inside redis. A Redis List looks like the following:
"Colum" => [0] c.mcgaley#gmail.com
[1] password
[2] Something
I am building an app in which I encountered the same problem. I solved it by having a list for all the user's info, and then have a key with the user's email with a value of the user's id. So my database would something like this:
"Colum" => [0] c.mcgaley#gmail.com
[1] password
[2] Something
"c.mcgaley#gmail.com" => "Colum"
So I could query the ID or the Email and still get the information I needed.
Sorry that I was not able to directly answer your question. Just hope this helped.