Is it possible to have dynamic database links in Oracle? I am using Oracle9i database.
Let me illustrate by what I require.
I have several views that are formed using dblinks.
For example:
CREATE VIEW MYVIEW AS SELECT * FROM TABLE#MYDBLINK.WORLD
mydbLINK.WORLD NEEDS TO POINT TO DIFFERENT INSTANCES OF THE DATABASE. SO AT ONE POINT IT MUST POINT TO THE DATABASESERVER1 AND THEN IT MUST SWITCH TO DATABASESERVER2.
Currently we are doing this by dropping the link and recreating it. When we do this, we have to recompile all the objects, refresh all the snapshots. Is it possible to avoid the dropping and recreating? I understand as soon as teh view changes, I will have to recompile the objects and refresh the snapshots regardless.
Has anyone implemented this feature?
Try using SYNONYMS as suggested by "Justin Cave" in this post.
Related
I am making a user form in Delphi for documents tracking application. I am interested in functionalities input new entry (record) and view list by... (date, name of document, ID,...).
My problem is that I don't know how to implement these functionalities for more than one user. Currently, I have 5 users. Each user has a unique input data (record) fields (columns) and view fields (columns) of each user are also unique. There could be more users.
So, how to implement these functionalities for this form? How to assign different data (fields) for each separate user for input and view? That is what I don't understand. Is that distributed functionality of an application? If yes, how to achieve it?
Note that I don't want static assigning of a user in application's code, e.g:
if(username='user1') then {
input();
view();
}
else if (username='user2') then {...}
...
because, than, every time there is a new user, developer must go back to the application's code and hard-code it. That is not efficient and is a bad implementation. Rather, I want that to be dynamic (if that is the right term). How to achieve this?
Note: I am using dbExpress tool with MySQL DBMS with RAD Studio XE7 Architect.
If I'm correctly understanding what you are asking, it seems as if you are unfamiliar with the idea of tables/datasets which operate in a so-called Master-Detail relationship. These are very easy to set up in Delphi.
Once you get familar with M->D relationships, I think you'll realise that what you should have been asking about is how to set one up in your app, rather than the problem of hard-coding of individual users into your form.
In your case, what you are missing at the moment is a table of users' details. Let's call that the Users table. Usually this would contain their name, obviously, and some kind of unique identifier (best is a "Primary key" in the Users database table), but NOT, please, their password to access the db, especially not in plain text.
Once your Users table is created, you can create a display grid (TDBGrid) and input/editing form for it.
Then, if you don't have it already, you could set up a grid and editing form for users' documents (which I'm going to refer to as the Documents table).
Once that's done, the main thing left to do is to set up in your Delphi project a Master-Detail relationship between your Users table (the master) and your Documents table (the detail).
If you prefer you can have a single form with two grids, the Users grid and the Documents grid on it, and as you scroll through the Users grid, you'll see that the Documents grid shows only their document records.
The details of how to set up a Master-Detail vary somewhat according to the type of table/dataset you're using so you'll need to search online for the details of how to do it. Broadly, it's a matter of connecting a TDataSource to your Users table and setting the DataSource (or MasterSource) property of your Documents table to point at the Users TDataSource, and then setting a couple of other, table-type-dependent properties of the Documents table.
Every edition of Delphi since well before D7 has come with a demo app, "MastApp" which illustrates how you use Master-Detail relationship amongst a number of tables. I suggest you take a look at the MastApp for your Delphi version and then look into how to set up M->D relationships for the type of Delphi dataset you are actually using.
I've been using a UIManagedDocument inside of a Singleton class. I create, open and perform with etc and everything was going fine until I needed to have two separate Data stores with an identical Schema. I've made sure everything was done in the same way through the same class (simply storing the second Database in a second static variable and using a BOOL to ensure the correct document gets used.
The problem is that while my original document works fine and the second document gets created fine, I can never seem to get the second document to open when I call 'openWithCompletionHandler' and pass in the block I need it to perform.
So my question is: Are there any special considerations I need to take into account when using multiple UIManagedDocuments in the one project?
Thanks in advance.
Yes there are. The big one is to make sure they both have unique NSPersistentStoreUbiquitousContentNameKey values set in the document's persistentStoreOptions.
See Rich Warren's well documented example:
Syncing Multiple Core Data Documents Using iCloud
And also my GitHub repo that makes multiple documents easier to set up and maintain in some cases:
APManagedDocument
In my program I have multiple databases. One is fixed and cannot be changed, but there are also some others, the so called user databases.
I thought now I have to start for every database one connection and to connect to each data dictionary. How is it possible to connect to more than one database with one connection by handing over the data dictionary filename? Btw. I am using a local server.
thank you very much,
André
P.S.: Okay I might find the answer to my problem.
The Key word is CreateDDLink. The procedure is connecting to another data dictionary, but before a master dictionary has to be set.
Links may be what you are looking for as you indicated in the question. You can use the API or SQL to create a permanent link alias, or you can dynamically create links on the fly.
I would recomend reviewing this specific help file page: Using Tables from Multiple Data Dictionaries
for a permanent alias (using SQL) look at sp_createlink. You can either create the link to authenticate the current user or set up the link to authenticate as a specific user. Then use the link name in your SQL statements.
select * from linkname.tablename
Or dynamically you can use the following which will authenticate the current user:
select * from "..\dir\otherdd.add".table1
However, links are only available to SQL. If you want to use the table directly (i.e. via a TAdsTable component) you will need to create views. See KB 080519-2034. The KB mentions you can't post updates if the SQL statement for the view results in a static cursor, but you can get around that by creating triggers on the view.
I'm building a web app for bookmark storage with a directory system.
I've already got these collections set up:
Path(s)
---> Directories (embedded documents)
---> Links (embedded documents)
User(s)
So performance wise, should I:
- add the user id to the created path
- embed the whole Paths collection into the specific user
I want to pick option 2, but yeah, I dunno...
EDIT:
I was also thinking about making the whole interface ajaxified. So, that means I'll load the directories and links from a specific path (from the logged in user) through ajax. That way, it's faster and I don't have to touch the user collection. Maybe that changes things?
Like I've said in the comments, 1 huge collection in the whole database seems kinda strange. Right?
Well the main purpose of the mongoDB is to support redundant data.I will recommend second option is better because In your scenario what I feel that if you embed path collection into the specific user then by using only single query you can get all data about user as well as related to path collection as well.
And if you follow first option then you have to fire two separates queries to get all data which will increase your work somewhat.
As mongodb brings data into the RAM so after getting data from one collection you can store it into cursor and from that cursor data you can fetch data from another collection. So if we see performance wise I dont think it will affect a lot.
RE: the edit. If you are going to store everything in a single doc and use embedded docs, then when you make your queries make sure you just select the data you need, otherwise you will load the whole doc including the embedded docs.
I am trying to show/load different editor on different rows of a editorgridpanel. Like a textbox on one row combobox/superboxselect on another and it could be any order, random.
The conditions which dictate which editor will be shown reside in the database.
Please tell me if this is possible and if so, how do i go about it.. I have tried pulling the conditions asynchronously which are pulled on a click event for the respective column, but calling it async causes problems. Please advise
Anything is possible, but what you want to do would take a bit of work. The basic idea would be to configure the needed grid editor(s) dynamically and update the columns with the new editors when needed. Now... what would be required to make that actually work I couldn't say offhand without digging into the Ext source -- it would almost definitely require overriding default behavior in the grid and/or column model.
Pulling your conditions asynchronously would (I imagine) be too slow for the interaction of clicking on a row to edit inline. If it takes a second or more from click to configured editors, that would not be acceptable performance. I would try to find a way to send your conditions down along with the other row data if at all possible (they can be in the store's data model on the client without having to be shown in the grid).
Without knowing more about your business requirements, it might be more appropriate to ditch the editable grid and instead go with a dynamically-configured FormPanel tied to the grid. This way the interaction of clicking and then pausing slightly while the form is configured would appear to be more natural. Also, the functionality of rendering a form with a particular configuration is perfectly standard and would require nothing fancy on your end. See this example as a starting point (your form would be dynamic, but maybe the same type of interaction could work?)