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OTN Appreciation Day : APEX

Dimitri Gielis Blog - Tue, 10/11/2016 - 20:41
If you're following some Oracle blogs or Twitter, you'll see many blog posts starting with "OTN Appreciation Day : " today. You can read the story behind this initiative on Tim Hall's blog. "The blog post content should be short, focusing more on why you like the feature, rather than technical content."
In my life Oracle played (and is still playing) an important role... and it all started because I love working with data - which lead me to the Oracle database, the *best* database in the world.

So I just have to write about a feature of the Oracle Database; but which one to pick? The way Oracle implemented SQL, or the programming language inside the database PL/SQL or the tools and options that make the database awesome?... I thought some time about it and for me personally next to the database itself, it was really APEX that changed my life, so I just have to write about it.

In this post I want to share why I love Oracle Application Express (APEX) and why I consider this the best feature of the Oracle Database *ever*.

The goal, I believe, of a database is to capture data and do something with it; either to get insight in your data or share it again in different formats with others... and Oracle Application Express is just the easiest way to do this! In no time you create a web application with some forms that capture data directly in your database. And in even less time you share and get insight in your data through beautiful reports and charts. You just need a browser... it's secure, fast, scalable and you can use the full power and features of the database - APEX is the window to your data!


Oracle 12c: Indexing JSON in the Database Part II (Find A Little Wood)

Richard Foote's Blog - Fri, 08/05/2016 - 07:00
In Part I, we looked at how you can now store JSON documents within the Oracle 12c Database. For efficient accesses to JSON documents stored in the Oracle database, we can either create a function-based index based on the JSON_VALUE function or on JSON .dot notation. These indexes are useful for indexing specific JSON attributes, […]

Installing SQLcl on OEL/RHEL

Dimitri Gielis Blog - Thu, 08/04/2016 - 21:56
In my previous post I talked about how SQLcl came in handy to work with JavaScript against the database.

The installation of SQLcl is easy... you just download the zip, unpack and run the executable.

But to be fair, before I got SQLcl running (especially the script part) I encountered a number of issues, so hopefully this post helps you be able to run SQLcl with all features in minutes as it's meant to be :)

Those were the error messages I received when running sql (script):

javax.script.ScriptException: sun.org.mozilla.javascript.EvaluatorException: Java class "java.util.ArrayList" has no public instance field or method named "0".
javax.script.ScriptException: sun.org.mozilla.javascript.EcmaError: ReferenceError: "Java" is not defined. (#1) in at line number 1
The solution for me was to upgrade my Java version to Java 8.

Here're the steps on my OEL/RHEL system to upgrade Java:

$ cd /opt
$ wget --no-cookies --no-check-certificate --header "Cookie: gpw_e24=http%3A%2F%2Fwww.oracle.com%2F; oraclelicense=accept-securebackup-cookie" "http://download.oracle.com/otn-pub/java/jdk/8u102-b14/jdk-8u102-linux-x64.tar.gz"
$ tar xzf jdk-8u102-linux-x64.tar.gz 
$ cd jdk1.8.0_102/
$ alternatives --install /usr/bin/java java /opt/jdk1.8.0_102/bin/java 2$ alternatives --config java
There are 5 programs which provide 'java'.
  Selection    Command-----------------------------------------------   1           /usr/lib/jvm/jre-1.7.0-openjdk.x86_64/bin/java   2           /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java   3           /usr/lib/jvm/jre-1.5.0-gcj/bin/java*+ 4           /usr/java/jre1.8.0_101/bin/java   5           /opt/jdk1.8.0_102/bin/java
Enter to keep the current selection[+], or type selection number: 5
$ alternatives --install /usr/bin/jar jar /opt/jdk1.8.0_102/bin/jar 2$ alternatives --install /usr/bin/javac javac /opt/jdk1.8.0_102/bin/javac 2$ alternatives --set jar /opt/jdk1.8.0_102/bin/jar$ alternatives --set javac /opt/jdk1.8.0_102/bin/javac$ java -versionjava version "1.8.0_102"Java(TM) SE Runtime Environment (build 1.8.0_102-b14)Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)

$ export JAVA_HOME=/opt/jdk1.8.0_102$ export JRE_HOME=/opt/jdk1.8.0_102/jre$ export PATH=$PATH:/opt/jdk1.8.0_102/bin:/opt/jdk1.8.0_102/jre/bin
Now when running SQLcl everything worked like a charm. Hurray :)

SQLcl to the rescue when the Database and APEX fail (with JSON limitations)

Dimitri Gielis Blog - Thu, 08/04/2016 - 21:36
In the last two years I've been using JSON in almost every project I was involved in.
For example with APEX Office Print our plugin is sending JSON to the backend. This JSON you can actually see yourself in the Remote Debug screen in your AOP Dashboard.
Another example is the wearables project (IoT) I showed at KScope 16; the wearable is sending data to a smartphone or tablet, which in his turn is doing a call to our backend (in ORDS) and sending JSON across.

At the end of the day we want the data in the Oracle Database, so our APEX apps can work with that data.

Since Oracle DB 12c, JSON is supported straight from the database. I wrote a number of blog posts how to read JSON from SQL within the database. Here's a quick demo of JSON in the database:

SQL> create table tbl_with_json (  2    json_clob  clob,   3    constraint json_clob_chk check (json_clob is json)  4  );
Table TBL_WITH_JSON created.
SQL> SQL> insert into tbl_with_json (json_clob) values ('{  2      "items": [{  3          "client_id": -1,  4          "registration_date": "2016-07-29T07:46:09.941Z",  5          "question": "My Question",  6          "description": "My huge clob"  7      }]  8  }');
1 row inserted.
SQL> SQL> select a.json_clob.items.question as question, a.json_clob.items.description as description   2    from tbl_with_json a;
QUESTION----------------------------------------------------------------------------------------------------------------------------------------------------------------------DESCRIPTION----------------------------------------------------------------------------------------------------------------------------------------------------------------------My Question                                                                                                                                                           My huge clob                                                                                                                                                          

Now the reason of this blog posts: what if your JSON contains some very big text (>32K) in a single node e.g. in the description field? 
If you want to follow along in your own test case, open the description record in SQL Developer for example and past a large text (>32K) in the description node (so replace "My huge clob" with some other big text). Tip: For my test cases I typically use a Lorem Ipsum generator where I can specify the number of characters for example 33000 characters.

How can we parse this JSON and store for example the content of that in a CLOB field?
As I'm on 12c, should be simple right? The database is supporting reading JSON from SQL, so I first tried with JSON_TABLE, but there you can only define VARCHAR2 or NUMBER as data type, no CLOB, so went with VARCHAR2.
Here's the result:
SQL> select jt.question, jt.description  2    from tbl_with_json,   3         json_table(json_clob, '$.items[*]'  4           columns (  5             question     varchar2 path '$.question',  6             description  varchar2 path '$.description'  7           )  8*        ) as jt;
QUESTION----------------------------------------------------------------------------------------------------------------------------------------------------------------------DESCRIPTION----------------------------------------------------------------------------------------------------------------------------------------------------------------------My Question                                                                                                                                                                                                                                                                                                                                 

Oracle just returns null (nothing - blank) for the description!
But it's definitely not blank:

Next I tried the query like in my initial example, but the result was the same:
SQL> select a.json_clob.items.question as question, a.json_clob.items.description as description   2    from tbl_with_json a;
QUESTION----------------------------------------------------------------------------------------------------------------------------------------------------------------------DESCRIPTION----------------------------------------------------------------------------------------------------------------------------------------------------------------------My Question                                                                                                                                                                                                                                                                                                                                 

So the database will return a value when there's less than 4K (or possibly 32K depending the setting of your varchar2 size in the database) and it returns null when it's over this limit.
Hopefully Oracle Database 12.2 fixes this issue, but at the moment there's no native way to get to that data by using the Oracle supplied JSON functions. 
Edit 4-AUG: return null is default behaviour of Oracle, but you can specify you want an error instead. See the comments of Alex and Beda.
Ok, what can we try next?...
Since Oracle Application Express 5, APEX comes with a very nice package to work with JSON, APEX_JSON. This package has been heaven for us, especially with AOP.So I thought to try to use the APEX_JSON.PARSE and store it in a temporary JSON so I can read it with the get_clob_output method:
SQL> declare  2    l_data clob;  3    l_json apex_json.t_values;  4    l_return clob;  5  begin  6    select json_clob  7      into l_data  8      from tbl_with_json;  9    apex_json.parse(l_json, l_data) ; 10    apex_json.initialize_clob_output(dbms_lob.call, true, 0) ; 11    apex_json.open_object; 12    apex_json.write(l_json, 'items[1].description') ; 13    apex_json.close_object; 14    l_return := apex_json.get_clob_output; 15    apex_json.free_output; 16  end; 17  /
Error starting at line : 1 in command -declare  l_data clob;  l_json apex_json.t_values;  l_return clob;begin  select json_clob    into l_data    from tbl_with_json;  apex_json.parse(l_json, l_data) ;  apex_json.initialize_clob_output(dbms_lob.call, true, 0) ;  apex_json.open_object;  apex_json.write(l_json, 'items[1].description') ;  apex_json.close_object;  l_return := apex_json.get_clob_output;  apex_json.free_output;end;Error report -ORA-20987: Error at line 6, col 18: value exceeds 32767 bytes, starting at Lorem ipsum dolor sit amet, consectetuer adipiscinORA-06512: at "APEX_050000.WWV_FLOW_JSON", line 928ORA-06512: at "APEX_050000.WWV_FLOW_JSON", line 993ORA-06512: at line 9
But as you can see, there's a limit in there as well. So APEX 5 doesn't return null, but it returns an error. Hopefully a future version of APEX removes this limit ;)

When I work with data, I prefer to do it straight in the database, but now I was stuck. At those moments you have to go for a walk, get some sleep and talk to others to get more ideas... My preferred development languages (in this order) are APEX, SQL, PL/SQL, JavaScript, Node.js, ... (and then all others)
Then I remembered a blog post of Kris Rice that SQLcl has the ability to run JavaScript too because  SQLcl includes Nashorn (A Next-Generation JavaScript Engine for the JVM). So after looking at some SQLcl script examples, I wrote my own little SQLcl script that reads out the clob and puts it in a variable "content":
SQL> script  2     var Types = Java.type("java.sql.Types")  3     var BufferedReader = Java.type("java.io.BufferedReader")  4     var InputStreamReader = Java.type("java.io.InputStreamReader")  5       6     var GET_CLOB = "declare " +   7                    "   l_clob CLOB; " +   8                    " begin " +   9                    "   select json_clob " +  10                    "    into l_clob " +  11                    "    from tbl_with_json; " + 12                    "   ? := l_clob;" +  13                    " end;";  14   15     var cs = conn.prepareCall(GET_CLOB); 16     cs.registerOutParameter(1, Types.CLOB); 17     cs.execute(); 18     var clob = cs.getClob(1); 19     cs.close(); 20   21     var r = new BufferedReader(new InputStreamReader(clob.getAsciiStream(), "UTF-8")) 22     var str = null;  23     var content = ""; 24     while ((str = r.readLine()) != null) { content = content + str; } 25     ctx.write(content); 26  /{ "items": [{ "client_id": -1, "registration_date": "2016-07-29T07:46:09.941Z", "question": "My Question", "description": "Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem. Nulla consequat massa quis enim. Donec pede justo, fring
So the above reads the content of the clob which contains the JSON.As we are in JavaScript I thought we can parse this JSON and navigate to the description field. Once we have it we store it in another table or do whatever we want with it.Cool if it would work, no? And it did! :)
So lets finish this example. First we create a table to store the description field (the very big text).
SQL> create table tbl_with_description (description clob);

Here's the final script that will store the description node to another table :- the ctx.write calls are there to send debug output- the obj.items[0].description is how we get to the description node and we store that in a bind variable and execute another insert statement to save the description value:
SQL> script  2    3  try {  4     var Types = Java.type("java.sql.Types")  5     var BufferedReader = Java.type("java.io.BufferedReader")  6     var InputStreamReader = Java.type("java.io.InputStreamReader")  7       8     var GET_CLOB = "declare " +   9                    "   l_clob CLOB; " +  10                    " begin " +  11                    "   select json_clob " +  12                    "    into l_clob " +  13                    "    from tbl_with_json; " + 14                    "   ? := l_clob;" +  15                    " end;";  16   17     var cs = conn.prepareCall(GET_CLOB); 18     cs.registerOutParameter(1, Types.CLOB); 19     cs.execute(); 20     var clob = cs.getClob(1); 21     cs.close(); 22   23     var r = new BufferedReader(new InputStreamReader(clob.getAsciiStream(), "UTF-8")) 24     var str = null;  25     var content = ""; 26     while ((str = r.readLine()) != null) { content = content + str; } 27     //ctx.write(content); 28   29     var obj = JSON.parse(content); 30     ctx.write("Question: " + obj.items[0].question + "\n"); 31     ctx.write("Description: " + obj.items[0].description + "\n"); 32   33     var binds =  {}; 34     binds.description = obj.items[0].description; 35   36     var ret = util.execute("insert into tbl_with_description (description) values (:description)", binds); 37   38     if (ret) { 39       ctx.write("Insert done!\n"); 40     } else { 41       ctx.write("Error :(\n"); 42       var err = util.getLastException();       43       ctx.write("\nERROR:" + err + "\n");   44     } 45   46  } catch(e){ 47      ctx.write(e +"\n") 48      e.printStackTrace(); 49  } 50   51  /Question: My QuestionDescription: Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis ... eu,Insert done!

SQL> select count(*) from tbl_with_description;
  COUNT(*)----------         1
SQL> select substr(description,1,50) from tbl_with_description;
SUBSTR(DESCRIPTION,1,50)                                                        --------------------------------------------------------------------------------Lorem ipsum dolor sit amet, consectetuer adipiscin                              
I was blown away by this... and I see a lot of potential be able to run JavaScript against the database.
There's actually a way to load Nashorn in your database too, so you can do JavaScript, Node.JS etc. straight from your database. Nashorn came with Java 8, but it should run in Java 7 too, now the default version of Java in the Oracle Database is 6, so there're some extra steps to do to get it to work. Running JavaScript from the database is something I've on my list to do R&D in and I actually submitted an abstract to KScope17 where I will present my results on this topic (if it gets accepted!) :) 
So to recap this (longer) blog posts:1) JSON is being used a lot these days and having the possibility to work with JSON in the Oracle database is very nice, but as we have seen in the above example, it can't do everything yet. It has a real issue with large nodes.2) Knowing other languages and thinking out-of-the-box might come in handy; I would even say that JavaScript becomes more and more important for an APEX developer.3) SQLcl is a great tool, if you don't use it yet, I would definitely recommend looking into it. 4) Oracle Nashorn opens up an entire new set of possibilities.
In the last paragraph of this blog post I want to thank Kris Rice for his help understanding SQLcl script. Although there are many examples, it took me some time to get going and I did struggle to understand how to get to error messages for example. Although it's mostly JavaScript in the script, having some Java knowledge makes it easier. Time to refresh that a bit, it has been 15 years ago I did some real Java coding.
Hope this blog post will help you work with JSON and JavaScript within an Oracle context.

Edit 4-AUG: read the comments section for a way to get the CLOB out with PL/JSON.

Oracle 12c: Indexing JSON In The Database Part I (Lazarus)

Richard Foote's Blog - Tue, 08/02/2016 - 05:42
One of the very cool new features introduced in Oracle Database 12c Rel 1 is the ability to store JavaScript Object Notation (JSON) documents within the database. Unlike XML which has its own data type, JSON data can be stored as VARCHAR2, CLOB or BLOB data types, but with a JSON check constraint to ensure the […]

Index Advanced Compression: Multi-Column Index Part II (Blow Out)

Richard Foote's Blog - Thu, 09/24/2015 - 08:00
I previously discussed how Index Advanced Compression can automatically determine not only the correct number of columns to compress, but also the correct number of columns to compress within specific leaf blocks of the index. However, this doesn’t mean we can just order the columns within the index without due consideration from a “compression” perspective. As […]

Index Advanced Compression: Multi-Column Index Part I (There There)

Richard Foote's Blog - Thu, 09/17/2015 - 06:57
I’ve discussed Index Advanced Compression here a number of times previously. It’s the really cool additional capability introduced to the Advanced Compression Option with, that not only makes compressing indexes a much easier exercise but also enables indexes to be compressed more effectively than previously possible. Thought I might look at a multi-column index to highlight just […]
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