SQL

Change the size of ORE PNG graphics using in-database R functions

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In a previous blog post I showed you how create and display a ggplot2 R graphic using SQL. Make sure to check it out before reading the rest of this blog post.

In my previous blog post, I showed and mentioned that the PNG graphic returned by the embedded R execution SQL statement was not the same as what was produced if you created the graphic in an R session.

Here is the same ggplot2 graphic. The first one is what is produced in an R session and the section is what is produced by SQL query and the embedded R execution in Oracle.

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As you can see the second image (produced using the embedded R execution) gives a very square image.

The reason for this is that Oracle R Enterprise (ORE) creates the graphic image in PNG format. The default setting from this is 480 x 480. You will find this information when you go digging in the R documentation and not in the Oracle documentation.

So, how can I get my ORE produced graphic to appear like what is produced in R?

What you need to do is to change the height and width of the PNG image produced by ORE. You can do this by passing parameters in the SQL statement used to call the user defined R function, that in turn produces the ggplot2 image.

In my previous post, I gave the SQL statement to call and produce the graphic (shown above). One of the parameters to the rqTableEval function was set to null. This was because we didn’t have any parameters to pass, apart from the data set.

We can replace this null with any parameters we want to pass to the user defined R function (demo_ggpplot). To pass the parameters we need to define them using a SELECT statement.

cursor(select 500 as "ore.png.height", 850 as "ore.png.width" from dual),

The full SELECT statement now becomes

select *
from table(rqTableEval( cursor(select * from claims),
                        cursor(select 500 as "ore.png.height", 850 as "ore.png.width" from dual),
                        'PNG',
                        'demo_ggpplot'));

When you view the graphic in SQL Developer, you will get something that looks a bit more like what you would expect or want to see.

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For each graphic image you want to produce using ORE you will need to figure out that are the best PNG height and width settings to use. Plus it also depends on what tool or application you are going to use to display the images (eg. APEX etc)

Checking out the Oracle Reserved Words using V$RESERVED_WORDS

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When working with SQL or PL/SQL we all know there are some words we cannot use in our code or to label various parts of it. These languages have a number of reserved words that form the language.

Somethings it can be a challenge to know what is or isn’t a reserved word. Yes we can check the Oracle documentation for the SQL reserved words and the PL/SQL reserved words. There are other references and list in the Oracle documentation listing the reserved and key words.

But we also have the concept of Key Words (as opposed to reserved words). In the SQL documentation these are are not listed. In the PL/SQL documentation most are listed.

What is a Key Word in Oracle ?

Oracle SQL keywords are not reserved. BUT Oracle uses them internally in specific ways. If you use these words as names for objects and object parts, then your SQL statements may be more difficult to read and may lead to unpredictable results.

But if we didn’t have access to the documentation (or google) how can we find out what the key words are. You can use the data dictionary view called V$RESERVED_WORDS.

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But this view isn’t available to version. So if you want to get your hands on it you will need the SYS user. Alternatively if you are a DBA you could share this with all your developers.

When we query this view we get 2,175 entries (for 12.1.0.2 Oracle Database).

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Creating ggplot2 graphics using SQL

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Did you read the title of this blog post! Read it again.

Yes, Yes, I know what you are saying, “SQL cannot produce graphics or charts and particularly not ggplot2 graphics”.

You are correct to a certain extent. SQL is rubbish a creating graphics (and I’m being polite).

But with Oracle R Enterprise you can now produce graphics on your data using the embedded R execution feature of Oracle R Enterprise using SQL. In this blog post I will show you how.

1. Pre-requisites

You need to have installed Oracle R Enterprise on your Oracle Database Server. Plus you need to install the ggplot2 R package.

In your R session you will need to setup a ORE connection to your Oracle schema.

2. Write and Test your R code to produce the graphic

It is always a good idea to write and test your R code before you go near using it in a user defined function.

For our (first) example we are going to create a bar chart using the ggplot2 R package. This is a basic example and the aim is to illustrate the steps you need to go through to call and produce this graphic using SQL.

The following code using the CLAIMS data set that is available with/for Oracle Advanced Analytics. The first step is to pull the data from the table in your Oracle schema to your R session. This is because ggplot2 cannot work with data referenced by an ore.frame object.

data.subset <- ore.pull(CLAIMS) 

Next we need to aggregate the data. Here we are counting the number of records for each Make of car.

aggdata2 <- aggregate(data.subset$POLICYNUMBER,
                      by = list(MAKE = data.subset$MAKE),
                      FUN = length)

Now load the ggplot2 R package and use it to build the bar chart.

ggplot(data=aggdata2, aes(x=MAKE, y=x, fill=MAKE)) + 
       geom_bar(color="black", stat="identity") +
       xlab("Make of Car") + 
       ylab("Num of Accidents") + 
       ggtitle("Accidents by Make of Car")

The following is the graphic that our call to ggplot2 produces in R.

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At this point we have written and tested our R code and know that it works.

3. Create a user defined R function and store it in the Oracle Database

Our next step in the process is to create an in-database user defined R function. This is were we store R code in our Oracle Database and make this available as an R function. To create the user defined R function we can use some PL/SQL to define it, and then take our R code (see above) and in it.

BEGIN
   -- sys.rqScriptDrop('demo_ggpplot');
   sys.rqScriptCreate('demo_ggpplot', 
      'function(dat) {
         library(ggplot2)
         
         aggdata2 <- aggregate(dat$POLICYNUMBER,
                      by = list(MAKE = dat$MAKE),
                      FUN = length)

        g <-ggplot(data=aggdata2, aes(x=MAKE, y=x, fill=MAKE)) + geom_bar(color="black", stat="identity") +
                   xlab("Make of Car") + ylab("Num of Accidents") + ggtitle("Accidents by Make of Car")

        plot(g)
   }');
END;

We have to make a small addition to our R code. We need need to include a call to the plot function so that the image can be returned as a BLOB object. If you do not do this then the SQL query in step 4 will return no rows.

4. Write the SQL to call it

To call our defined R function we will need to use one of the ORE SQL API functions. In the following example we are using the rqTableEval function. The first parameter for this function passes in the data to be processed. In our case this is the data from the CLAIMS table. The second parameter is set to null. The third parameter is set to the output format and in our case we want this to be PNG. The fourth parameter is the name of the user defined R function.

select *
from table(rqTableEval( cursor(select * from claims),
                        null,
                        'PNG',
                        'demo_ggpplot'));                        

5. How to view the results

The SQL query in Step 4 above will return one row and this row will contain a column with a BLOB data type.

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The easiest way to view the graphic that is produced is to use SQL Developer. It has an inbuilt feature that allows you to display BLOB objects. All you need to do is to double click on the BLOB cell (under the column labeled IMAGE). A window will open called ‘View Value’. In this window click the ‘View As Image’ check box on the top right hand corner of the window. When you do the R ggplot2 graphic will be displayed.

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Yes the image is not 100% the same as the image produced in our R session. I will have another blog post that deals with this at a later date.

But, now you have written a SQL query, that calls R code to produce an R graphic (using ggplot2) of our data.

6. Now you can enhance the graphics (without changing your SQL)

What if you get bored with the bar chart and you want to change it to a different type of graphic? All you need to do is to change the relevant code in the user defined R function.

For example, if we want to change the graphic to a polar plot. The following is the PL/SQL code that re-defines the user defined R script.

BEGIN
   sys.rqScriptDrop('demo_ggpplot');
   sys.rqScriptCreate('demo_ggpplot', 
      'function(dat) {
         library(ggplot2)
         
         aggdata2 <- aggregate(dat$POLICYNUMBER,
                      by = list(MAKE = dat$MAKE),
                      FUN = length)

         n <- nrow(aggdata2)
         degrees <- 360/n

        aggdata2$MAKE_ID <- 1:nrow(aggdata2)

        g<- ggplot(data=aggdata2, aes(x=MAKE, y=x, fill=MAKE)) + geom_bar(color="black", stat="identity") +
               xlab("Make of Car") + ylab("Num of Accidents") + ggtitle("Accidents by Make of Car") + coord_polar(theta="x") 
        plot(g)
   }');
END;

We can use the exact same SQL query we defined in Step 4 above to call the next graphic.

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All done.

Now that was easy! Right?

I kind of is easy once you have been shown. There are a few challenges when working in-database user defined R functions and writing the SQL to call them. Most of the challenges are around the formatting of R code in the function and the syntax of the SQL statement to call it. With a bit of practice it does get easier.

7. Where/How can you use these graphics ?

Any application or program that can call and process a BLOB data type can display these images. For example, I’ve been able to include these graphics in applications developed in APEX.

PREDICTION_DETAILS function in Oracle

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When building predictive models the data scientist can spend a large amount of time examining the models produced and how they work and perform on their hold out sample data sets. They do this to understand is the model gives a good general representation of the data and can identify/predict many different scenarios. When the “best” model has been selected then this is typically deployed is some sort of reporting environment, where a list is produced. This is typical deployment method but is far from being ideal. A more ideal deployment method is that the predictive models are build into the everyday applications that the company uses. For example, it is build into the call centre application, so that the staff have live and real-time feedback and predictions as they are talking to the customer.

But what kind of live and real-time feedback and predictions are possible. Again if we look at what is traditionally done in these applications they will get a predicted outcome (will they be a good customer or a bad customer) or some indication of their value (maybe lifetime value, possible claim payout value) etc.

But can we get anymore information? Information like what was reason for the prediction. This is sometimes called prediction insight. Can we get some details of what the prediction model used to decide on the predicted value. In more predictive analytics products this is not possible, as all you are told is the final out come.

What would be useful is to know some of the thinking that the predictive model used to make its thinking. The reasons when one customer may be a “bad customer” might be different to that of another customer. Knowing this kind of information can be very useful to the staff who are dealing with the customers. For those who design the workflows etc can then build more advanced workflows to support the staff when dealing with the customers.

Oracle as a unique feature that allows us to see some of the details that the prediction model used to make the prediction. This functions (based on using the Oracle Advanced Analytics option and Oracle Data Mining to build your predictive model) is called PREDICTION_DETAILS.

When you go to use PREDICTION_DETAILS you need to be careful as it will work differently in the 11.2g and 12c versions of the Oracle Database (Enterprise Editions). In Oracle Database 11.2g the PREDICTION_DETAILS function would only work for Decision Tree models. But in 12c (and above) it has been opened to include details for models created using all the classification algorithms, all the regression algorithms and also for anomaly detection.

The following gives an example of using the PREDICTION_DETAILS function.

select cust_id, 
       prediction(clas_svm_1_27 using *) pred_value,
       prediction_probability(clas_svm_1_27 using *) pred_prob,
       prediction_details(clas_svm_1_27 using *) pred_details
from mining_data_apply_v;

The PREDICTION_DETAILS function produces its output in XML, and this consists of the attributes used and their values that determined why a record had the predicted value. The following gives some examples of the XML produced for some of the records.

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I’ve used this particular function in lots of my projects and particularly when building the applications for a particular business unit. Oracle too has build this functionality into many of their applications. The images below are from the HCM application where you can examine the details why an employee may or may not leave/churn. You can when perform real-time what-if analysis by changing some of attribute values to see if the predicted out come changes.

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