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StarEast, InteropITX and GDPR

I’m getting ready to get on a plane between two events today and have been so busy, that there’s been a break in blogging.  That’s right folks, Kellyn has let a few things slide….

Pragma UDF – Some Current Limitations

There are currently some limitations to when pragma UDF will speed up your calls to PL/SQL functions from SQL.

In my post introducing the new pragma UDF feature of Oracle 12c I explained how it can be used to reduce the impact of context switching when you call a PL/SQL function from SQL.

In my example I showed how running a SQL-only SELECT statement that formatted a name for display over 100,000 records took 0.03 seconds went up to 0.33 seconds when the formatting SQL was put in a user defined PL/SQL function. This impact on performance is a shame as it is so beneficial to encapsulate business logic in one single place with PL/SQL. Stating that the PL/SQL function is a user defined one with the pragma UDF option reduced the run time to 0.08 seconds – which is removing most of the context switching overhead. Check out the prior post for full details.

Pragma UDF – Speeding Up your PL/SQL Functions Called From SQL

A new feature for PL/SQL was introduced in V12, pragma UDF. UDF stands for User Defined Functions. It can speed up any SQL you have that uses PL/SQL functions you created yourself.

{please see this second post on some limitations of pragma UDF in respect of IN & RETURN data types and parameter defaults}.

We can create our own functions in PL/SQL and they can be called from both PL/SQL and SQL. This has been possible since V7.3 and is used extensively by some sites to extend the capabilities of the database and encapsulate business logic.

PL/SQL bug with DBMS_RANDOM?

I think I’ve found an (admittedly obscure) bug with DBMS_RANDOM, group functions, PL/SQL and/or SQL.

Have a look and see if you also think this is odd – or have I missed the totally obvious?

(This is all on 12.1.0.2)

{Update – my conclusion is, and thanks to Joel and Sayan for their comments, that this is not a “bug”. Oracle do not promise us how PL/SQL functions are executed due to the way SQL can be re-written by the parser. I think most of us stumbling over something like this would treat it as a bug though. You have to look at the column projection, again see the comments, to see how Oracle is deciding to get the columns derived by a naked call to DBMS_RANDOM.VALUE (by naked I mean no inclusion of parameters passed in and, significantly, no reference to columns). It’s just the way it is}

Computers are Logical. Software is Not

We’ve all heard it before. Computers are totally logical, they do exactly what they are told. After all, Central Processing Units (CPUs) are built out of fundamental units called Logic Gates. With perhaps the exception when a stray cosmic ray gets lucky, the circuits in a computer chip and memory act in a totally logical and predicted manner.

And of course, anything built on top of computers will be utterly logical as well. All those robots that companies are designing & building to clean our houses, do our manual labour and fight our wars are going to be logical, follow the rules given and be sensible.

Exclusion of Unioned SQL in Views?

Question – you have a view definition of the following format:

select 1 as d_type, col_a,col_b,col_c
from TAB_X, TAB_Y, TAB_Z
where {your predicates}
UNION
select 2 as d_type, col_a,col_b,col_c
from TAB_P, TAB_Q, TAB_R
where {your predicates}
UNION
select 3 as d_type, col_a,col_b,col_c
from TAB_X X, TAB_Y, TAB_Z
where {your predicates}

You now select from the view and your code includes a filter predicate such as:

“WHERE D_TYPE = 1″

Friday Philosophy – Lead or Lag (When to Upgrade)?

I was involved in a discussion recently with Debra Lilley which version of Oracle to use. You can see her blog about it here (and she would love any further feedback from others). Oracle now has a policy that it will release the quarterly PSUs for a given point release for 12 months once that point release is superseded. ie once 11.2.0.3 came out, Oracle will only guarantee to provide PSUs for 11.2.0.2 for 12 months. See “My Oracle Support” note ID 742060.1. However, an older Terminal release such as 11.1.0.7 is not superseded and is supported until 2015 – and will get the quarterly PSU updates. This left the customer with an issue. Should they start doing their development on the latest and theoretically greatest version of Oracle and be forced to do a point upgrade “soon” to keep getting the PSUs, or use an older version of Oracle and avoid the need to upgrade?

New Defaults, Old Side Effects

When 11.2 came out I posted about deferred segment creation at http://orawin.info/blog/2010/04/25/new-features-new-defaults-new-side-effects/ and a couple of odd side effects. Oracle published a Note  1050193.1 that makes the quite extraordinary claim that Sequences are not guaranteed to generate all consecutive values starting with the ‘START WITH’ value. It’s absolutely true that sequences don’t guarantee no gaps – but [...]

Skipped Initial Sequence Value on Oracle 11.2

I’m seeing an oddity with newly created sequences skipping the initial value. ie I create the sequence and the first use of it returns the value 2, not 1.

{update, see the post comments and this post by Niall – this is a side effect of delayed segment creation – the first insert silently fails, but gets the sequence, and is repeated behind the scenes once the segment is there. It is fixed in 11.2.0.3, my db is at 11.2.0.1 as I got sick of the download of the latest version failing on my poor broadband connection and got it off a mate – turns out it is not the latest version.
Thanks for the enlightenment Niall.}

This is on Oracle 11.2.0.1 on Windows (XP, Vista and now Windows 7 64 bit). I am sure I did not see this on Oracle 10.1 and 10.2 on linux, Tru64 and windows.