ODI Hidden Gems – Temporary Indexes


Hi all!

Today’s gem is indeed a very hidden one. ODI is known (unfortunately) to be “not intuitive” most of the times and I think that’s because we have many options that are scared across too many objects in the UI, which leads you to keep clicking on objects until you find what you need. To make things a little bit harder, you have the logical and physical tabs and each one of them has its own representation of the objects, so some of the options will be in the logical tab, some others in the physical tab. Lets talk today about the “Temporary Indexes” option that exists in some objects in the Physical tab of a mapping.

Very often you will load data from places that may not have an “index” concept, like files for example. You may create a mapping that will load any number of big files, put them in a staging area and filter/join them together to do some ETL. You may reach situations where those joins are not performing well since you don’t have an “index” on the files. Here is where ODI may help you with some Temporary Indexes creation. Let’s see this example (it’s very basic, but you will get the idea):

1

You join both files and load to a target table. When we execute this mapping, this is what we get:

2

Basically, you are loading both files to C$ tables and then you are joining those C$ tables when loading to the target.

7

If you think that this join would benefit from an index creation, you may configure ODI to create temporary indexes on that join. To do that, you will need to go to physical tab, click the “join” object and go to “Properties” as below. After you know where the option is, it seems pretty easy and obvious, however if you are not familiar with ODI, you will need some practice to actually figure out that you need to go to physical tab and then click on the specific object to get some unique properties of that object:

3

Change Index Type to one of the possible values (Bitmap, Non-Unique, Unique) and run the mapping again. You will see the index creation after it loads the data to C$:

4

This technique also works for filters objects. If we add a filter in any of the file columns and if you think that it would be beneficial to have an index on it, the steps to create it  would be the same as before:

5When executing, we can see all the indexes creation there:

6

If you go to Oracle documentation, there is a note there regarding using the Temporary Index creation:

  • The creation of temporary indexes may be a time-consuming operation in the overall flow. Oracle recommends reviewing execution statistics and comparing the execution time saved by the indexes to the time spent creating them.

It’s a very valid point. Most of the time we don’t need to create any temporary index, but if you end up in one of those cases that you need to create them, now you know where to find this option.

Thanks!

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: