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Building community via the speaker community

I recently participated in the Oracle Developer Community Yatra tour throughout India. It is a hectic event with 7 cities covered in a mere 9 days, so you can imagine how frantic the pace was. A typical day would be:

  • 7am – breakfast
  • 8am – check out of hotel and leave for the venue
  • 9am – speak all day, host Q&A
  • 6pm – leave straight from venue to the airport
  • 8pm – dinner at airport, and fly to next city
  • 1am – get to next hotel, grab some sleep before doing it all again in 6 hours time

Yet as a speaker in this event, it never felt that the logistics of the event were out of control.  This is mainly due to the incredible work of the people in the AIOUG (All India Oracle User Group) coordinated by Sai Penumuru. The smoothness of the organization prompted me to blog about how user groups could follow the AIOUG lead in terms of running successful events.

Humble pie made with NULL strings

I was helping out a client a while back with an issue where a panicked email came into my inbox along the lines of “SELECT IS BROKEN IN ORACLE!!!”, which seemed perhaps a little extreme Smile. So I pursued it further asking for some concrete details, and I must concede it had me a little bamboozled for a while. I’ve simplified the example to keep it easy to digest, but the premise is the same.

My colleague had a table with a couple of VARCHAR2 columns:

image

Hyper-partitioned index avoidance thingamajig

As you can tell, I have no idea on a name for what I am about to describe. So let me start from the beginning, and set the scene for an idea I have to utilize a cool new 18c feature.

Often in a transactional-style system the busiest table (let us call it SALES for the sake of this discussion) is also

  • the biggest table, after all, it has all of our sales in it,
  • the most demanded for table, in that, almost every query in our application wants to access it in some way shape or form.

This is in effect the database version of the Pareto Principle. Everyone wants a slice of that SALES “pie”, and the piece of that pie that is in most demand is typically the most recent data. Your application may have pages that will be showing:

18.3 As easy as 1…2…3

Well, finally it’s here! 18c for on-premise installation so the world can all get stuck into the cool new features of the latest release on their own laptops Smile  At least that is what I’ll be doing!

Naturally as soon as I heard the news, I downloaded the software and got ready to set aside the day for installation and creation of an 18c database. But I didn’t need that long – I didn’t need that long at all. Just a few clicks and a few commands and there it was – my 18c database up and running.

Check out how easy it is with my three videos.

Software Installation

Searching in Oracle Database documentation

Just a quick heads up with something I see from time to time in Chrome (but not in Firefox or any other browser).

Occasionally when doing a search, the results are not limited as per my criteria.  For example, if I am searching for information about Spatial in the Licensing Guide:

image

then when I click the Search button, the results might come back with a far broader search range:

Complex materialized views and fast refresh

Just a quick discovery that came across the AskTOM “desk” recently. We have an outstanding bug in some instances of fast refresh materialized views when the definition of the materialized view references a standard view.

Here’s a simple demo of the issue – I’ll use a simplified version of the EMP and DEPT tables, linked by a foreign key in the usual way:

Standard Edition–different optimizer but still cool

One cool technique that the optimizer can employ is the BITMAP CONVERSION TO ROWIDS method to take advantage of B-tree indexes in a means that we would normally associate with a bitmap index. This can be particularly useful with multiple predicates on individually indexed columns because it lets us establish the rows of interest before having to visit the heap blocks.  Here’s an example of that in action, even when the indexes in question are Text indexes.

Enterprise Edition plan

UTL_FILE_DIR and 18c

I wrote a blog post called The Death of UTL_FILE which attracted a comment from a reader:

“There is NO chance to stay at UTL_FILE as it is DESUPPORTED starting with database Version 18c”

This is not the case, but since I wanted to clarify what has changed in 18c, it warrants this small but separate blog post. When UTL_FILE first into existence in Oracle 7, the concept of directory object did not apply to UTL_FILE. Clearly we could not just let UTL_FILE to write to any destination, otherwise a malicious person could write a little PL/SQL block like this:

More triggers are better

Yes, you heard me correctly. If you have got one trigger on a table, then you might be surprised to find that perhaps having a second one will be a better option. Then again, I also love the sweet scent of a clickbaity, inflammatory blog post title to draw the readers in Smile so you’ll just have to read on to see which is true.

DDL for constraints – subtle things

The DBMS_METADATA package is very cool. I remember the days of either hand-crafting DDL statements based on queries to the data dictionary, or many a DBA will be familiar with running “imp show=y” or “imp indexfile=…” in order to then laboriously extract the DDL required from the import log file.  DBMS_METADATA removed all of those annoyances to give us a simple API to get the true and complete DDL for a database object.

But when extracting DDL from the database using the DBMS_METADATA package, you need to be aware of some subtleties especially if you plan on executing that DDL in the database.