I'm endeavoring to develop an application that uses Oracle as the database back-end. The application will calculate several statistics from the various tables in the database. The front-end will most likely be a web application and this front-end will display various charts and calculated statistics. Now, I imagine that it would be more efficient to perform the calculations in the database rather than in the service layer because said calculations would need to be performed for every web request. That being the case, I'm not sure which mechanism to use. (e.g. stored procedure, function, view) To illustrate what I'm going for, suppose I want to keep statistics of student grades for many students. I would like to have a web interface that lets me view those statistics on student-by-student basis and also an all-inclusive basis. Some of the stats are dependent on aggregates (e.g. average, min, max) of all of the student grades and some stats are dependent only on an individual student. In this situation, every time a record is added or updated, the aggregates would have to be recalculated. So I am speculating that if I had a special table that held all of the calculated values I need and a trigger(s) to recalculate everything when a record is added/updated then all I would need to do from a web request point-of-view is have the service layer pull the desired values from this special table. I'm just not sure if this is the best way to go or not so I am asking the community for any input/advice. Note: Although I'm using Oracle, I'm open to using PostgreSQL or mySQL.
Thanks in advance
The scenario you are describing would be ideal for using materialized views. They can be designed to refresh automatically (and incrementally) every time the source data is updated by your application. The calculations would be built in to the view definition. No triggers required, and likely no stored procedures unless your calculations involve multiple steps. Check here: https://oracle-base.com/articles/misc/materialized-views and here: https://medium.com/oracledevs/lightning-fast-sql-with-real-time-materialized-views-12-things-developers-will-love-about-oracle-54bcc9eac358 for more info.
Related
So I will be embarking on designing a dashboard that will display KPI's and other relevant information for my team. Since I am in the early stages of this project and am not very familiar on the technical process behind designing a dashboard, I need some questions vetted out first before I go and shop for some solutions to avoid reinventing the wheel.
Here are some of my questions:
We want a dashboard that can provide live-time information via our data sources (or as close to live-time as possible). What function allows a dashboard to update itself with concurrent datasources? From a conceptual standpoint, I can understand creating a dashboard out of Microsoft Excel, and having the dashboard dependent on the values you may have set within your pivot table.
How do you make a dashboard request information from multiple datasources on its own? Just like the excel example, a user may have to go into the pivot tables to update values, but I want to know how would a dashboard request this by itself and what is the exact method from a programming standpoint? Does the code execute itself every time you refresh the webpage?
How do you create datasources organically? I know for some solutions such as SharePoint BI Center, there are pre-supported datasources like an excel sheet or SharePoint and it's as easy as uploading your document and letting the design handle the rest. However, there are going to be some datasources that I know that will need to be fetched. Do I need to understand something else like an event recorder in order to navigate this issue?
Introduction
The dashboard (or a report, respectively) is usually the result of a long chain of steps. Very much simplified it could look like this:
src1
|------\
src2 | /---- Dashboards
|------+---[DWH]-[BR]-+
src n | | \---- Reports etc.
|------/ [Big Data]
Keep in mind, this is only a very, very simple structure of a data backend / frontend.
DWH means Data Warehouse, where data might be stored temporarily (you referred to this as fetching). This could be a database, could be a Big Data engine, could be a combination of both...
Afterwards, there are Business Rules (BR). Those might be specific rules in how different departments calculate and relate to data, but also simple things like algebra.
Questions
So, the main question should not be about the technology:
What software should we choose?
How can we create a dashboard?
but on the contrary focused on your business processes (see it like a top-down view):
How does our core process look like? Where would I like to measure data?
How would department a calculate sales in difference to department b? Should all use the same rule?
Where does everyone store the data? Can we access it? Do we need structural data?
And, very easy to forget but also easily sometimes one of the biggest parts: Is the identifier of a business object (say, sales id) everywhere build and formatted in the same way?
Conclusion
When those questions are at least in the back of your head and you keep working in this direction, more or less automatically data will spill out at certain points of that process.
Then it won't matter if you use Excel, a small-to medium app like Tableau, Tibco Spotfire, QlikView, Power BI or you want to go full scale with a big Hadoop backend, databases and JasperReports, Apache Drill, Pentaho, SSIS on top of it... it will come out eventually.
TL;DR
Focus on the processes first. Make sure to understand them. Draft in Excel. Then proceed in getting the data and the tools you need to help your use cases. It will work out much better from a "top-down" approach than trying to solve your requirements with tools only.
So I was thinking... Imagine you have to write a program that would represent a schedule of a whole college.
That schedule has several dimensions (e.g.):
time
location
indivitual(s) attending it
lecturer(s)
subject
You would have to be able to display the schedule from several standpoints:
everything held in one location in certain timeframe
everything attended by individual in certain timeframe
everything lecturered by a certain lecturer in certain timeframe
etc.
How would you save such data, and yet keep the ability to view it from different angles?
Only way I could think of was to save it in every form you might need it:
E.g. you have folder "students" and in it each student has a file and it contains when and why and where he has to be. However, you also have a folder "locations" and each location has a file which contains who and why and when has to be there. The more angles you have, the more size-per-info ratio increases.
But that seems highly inefficinet, spacewise.
Is there any other way?
My knowledge of Javascript is 0, but I wonder if such things would be possible with it, even in this space inefficient form.
If not that, I wonder if it would work in any other standard (C++, C#, Java, etc.) language, primarily in Java...
EDIT: Could this be done by using MySQL database?
Basically, you are trying to first store data and then present it under different views.
SQL databases were made exactly for that: from one side you build a schema and instantiate it in a database to store your data (the language is called Data Definition Language, DDL), then you make requests on it with the query language (SQL), what you call "views". There are even "views" objects in SQL databases to build these views Inside the database (rather than having to the code of the request in the user code).
MySQL can do that for sure, note that it is possible to compile some SQL engine for Javascript (SQLite for example) and use local web store to store the data.
There is another aspect to your question: optimization of the queries. While SQL can do most of the request job for your views. It is sometimes preferred to create actual copies of the requests results in so called "datamarts" (this is called de-normalizing a request), so that the hard work of selecting or computing aggregate/groups functions and so on is done once per period of time (imagine that a specific view changes only on Monday), then requesters just have to read these results. It is important in this case to separate at least semantically what is primary data from what is secondary data (and for performance/user rights reasons, physical separation is often a good idea).
Note that as you cited MySQL, I wrote about SQL but mostly any database technology could do that what you searched to do (hierarchical, object oriented, XML...) as long as the particular implementation that you use is flexible enough for your data and requests.
So in short:
I would use a SQL database to store the data
make appropriate views / requests
if I need huge request performance, make appropriate de-normalized data available
the language is not important there, any will do
Looking for a bit of advice on how to optimise one of our projects. We have a ASP.NET/C# system that retrieves data from a SQL2008 data and presents it on a DevExpress ASPxGridView. The data that's retrieved can come from one of a number of databases - all of which are slightly different and are being added and removed regularly. The user is presented with a list of live "companies", and the data is retrieved from the corresponding database.
At the moment, data is being retrieved using a standard SqlDataSource and a dynamically-created SQL SELECT statement. There are a few JOINs in the statement, as well as optional WHERE constraints, again dynamically-created depending on the database and the user's permission level.
All of this works great (honest!), apart from performance. When it comes to some databases, there are several hundreds of thousands of rows, and retrieving and paging through the data is quite slow (the databases are already properly indexed). I've therefore been looking at ways of speeding the system up, and it seems to boil down to two choices: XPO or LINQ.
LINQ seems to be the popular choice, but I'm not sure how easy it will be to implement with a system that is so dynamic in nature - would I need to create "definitions" for each database that LINQ could access? I'm also a bit unsure about creating the LINQ queries dynamically too, although looking at a few examples that part at least seems doable.
XPO, on the other hand, seems to allow me to create a XPO Data Source on the fly. However, I can't find too much information on how to JOIN to other tables.
Can anyone offer any advice on which method - if any - is the best to try and retro-fit into this project? Or is the dynamic SQL model currently used fundamentally different from LINQ and XPO and best left alone?
Before you go and change the whole way that your app talks to the database, have you had a look at the following:
Run your code through a performance profiler (such as Redgate's performance profiler), the results are often surprising.
If you are constructing the SQL string on the fly, are you using .Net best practices such as String.Concat("str1", "str2") instead of "str1" + "str2". Remember, multiple small gains add up to big gains.
Have you thought about having a summary table or database that is periodically updated (say every 15 mins, you might need to run a service to update this data automatically.) so that you are only hitting one database. New connections to databases are quiet expensive.
Have you looked at the query plans for the SQL that you are running. Today, I moved a dynamically created SQL string to a sproc (only 1 param changed) and shaved 5-10 seconds off the running time (it was being called 100-10000 times depending on some conditions).
Just a warning if you do use LINQ. I have seen some developers who have decided to use LINQ write more inefficient code because they did not know what they are doing (pulling 36,000 records when they needed to check for 1 for example). This things are very easily overlooked.
Just something to get you started on and hopefully there is something there that you haven't thought of.
Cheers,
Stu
As far as I understand you are talking about so called server mode when all data manipulations are done on the DB server instead of them to the web server and processing them there. In this mode grid works very fast with data sources that can contain hundreds thousands records. If you want to use this mode, you should either create the corresponding LINQ classes or XPO classes. If you decide to use LINQ based server mode, the LINQServerModeDataSource provides the Selecting event which can be used to set a custom IQueryable and KeyExpression. I would suggest that you use LINQ in your application. I hope, this information will be helpful to you.
I guess there are two points where performance might be tweaked in this case. I'll assume that you're accessing the database directly rather than through some kind of secondary layer.
First, you don't say how you're displaying the data itself. If you're loading thousands of records into a grid, that will take time no matter how fast everything else is. Obviously the trick here is to show a subset of the data and allow the user to page, etc. If you're not doing this then that might be a good place to start.
Second, you say that the tables are properly indexed. If this is the case, and assuming that you're not loading 1,000 records into the page at once and retreiving only subsets at a time, then you should be OK.
But, if you're only doing an ExecuteQuery() against an SQL connection to get a dataset back I don't see how Linq or anything else will help you. I'd say that the problem is obviously on the DB side.
So to solve the problem with the database you need to profile the different SELECT statements you're running against it, examine the query plan and identify the places where things are slowing down. You might want to start by using the SQL Server Profiler, but if you have a good DBA, sometimes just looking at the query plan (which you can get from Management Studio) is usually enough.
What is the best way in terms of speed of the platform and maintainability to access data (read only) on Dynamics CRM 4? I've done all three, but interested in the opinions of the crowd.
Via the API
Via the webservices directly
Via DB calls to the views
...and why?
My thoughts normally center around DB calls to the views but I know there are purists out there.
Given both requirements I'd say you want to call the views. Properly crafted SQL queries will fly.
Going through the API is required if you plan to modify data, but it isnt the fastest approach around because it doesnt allow deep loading of entities. For instance if you want to look at customers and their orders you'll have to load both up individually and then join them manually. Where as a SQL query will already have the data joined.
Nevermind that the TDS stream is a lot more effecient that the SOAP messages being used by the API & webservices.
UPDATE
I should point out in regard to the views and CRM database in general: CRM does not optimize the indexes on the tables or views for custom entities (how could it?). So if you have a truckload entity that you lookup by destination all the time you'll need to add an index for that property. Depending upon your application it could make a huge difference in performance.
I'll add to jake's comment by saying that querying against the tables directly instead of the views (*base & *extensionbase) will be even faster.
In order of speed it'd be:
direct table query
view query
filterd view query
api call
Direct table updates:
I disagree with Jake that all updates must go through the API. The correct statement is that going through the API is the only supported way to do updates. There are in fact several instances where directly modifying the tables is the most reasonable option:
One time imports of large volumes of data while the system is not in operation.
Modification of specific fields across large volumes of data.
I agree that this sort of direct modification should only be a last resort when the performance of the API is unacceptable. However, if you want to modify a boolean field on thousands of records, doing a direct SQL update to the table is a great option.
Relative Speed
I agree with XVargas as far as relative speed.
Unfiltered Views vs Tables: I have not found the performance advantage to be worth the hassle of manually joining the base and extension tables.
Unfiltered views vs Filtered views: I recently was working with a complicated query which took about 15 minutes to run using the filtered views. After switching to the unfiltered views this query ran in about 10 seconds. Looking at the respective query plans, the raw query had 8 operations while the query against the filtered views had over 80 operations.
Unfiltered Views vs API: I have never compared querying through the API against querying views, but I have compared the cost of writing data through the API vs inserting directly through SQL. Importing millions of records through the API can take several days, while the same operation using insert statements might take several minutes. I assume the difference isn't as great during reads but it is probably still large.
If we put aside the rights and wrongs of putting demo data into a live system for a minute (that's a whole separate discussion!), we are being asked to store some demo data in our live system so that it can be credibly demonstrated without the appearance of smoke + mirrors (we want to use the same login page for example)
Since I'm sure this is a challenge many other people must have - I'd be interested to know what approaches have people have devised to separating this data so that it doesn't get in the way of day to day operations on their systems?
As I alluded to above, I'm aware that this probably isn't best practice. :-)
Can you instead, segregate the data into a new database, and just redirect your connection strings (they're not hard-coded, right? right?) to point to the demo database. This way, live data isn't tainted, and your code looks identical. We actually do a three tier-deployment system this way, where we do local development, deploy to QC environments that have snapshots of the live data every few months, and then deploy to live when testing is complete.
FWIW, we're looking at using Oracle's row level security / virtual private database feature to seperate the demo data from the rest.
I've often seen it on certain types of live systems.
For example, point of sale systems in a supermarket: cashiers are trained on the production point of sale terminals.
The key is to carefully identify the test or training data. I wouldn't say that there's any explicit best practice for how to model this in a database - it's going to be applicaiton specific.
You really have to carefully define the scope of what is covered by the test/training scenarios. For example, you don't want the training/test transactions to appear in production reports (but you may want to be able to create reports with this data for training/test purposes).
Completely disagree with Joe. Oracle has a tool to do this regardless of implementation. Before I read your answer I was going to say VPD... But that could have an impact on Production.
Remember Every table in a query changes from
SELECT * FROM tableA
to
SELECT * FROM (SELECT * FROM tableA WHERE Data_quality = 'PROD' <or however you do it>
Every table with a policy that is...
So assuming your test data has to span EVERY table, every table will have to have a policy and every table will be filtered before a SQL can begin working.
You can even hide that column from the users. You'll need to write the policy with some deftness if you do. You'll have to create that value based on how the data is inserted and expose the column to certain admin accounts for maintenance.