Soon a small black box will enter our living rooms, and that will
change the way we spend time in front of TVs forever. It will
happen on Nov. 4, 2010, and the name of this phenomenon is Kinect.
In my student days I was an avid gamer and has played virtually all
“big” games that came out for PC, luckily for me those days it
wasn’t such a flood as now. And I remember well the events that
changed the game industry as we knew it. Those milestones were:
- Doom - the first popular first-person shooter, 1993;
- 3dfx Voodoo - the first 3D accelerator, 1996;
- Nvidia GeForce 256 - the first 3D accelerator with integrated
geometry GPU, 1999.
After that, I stopped actively playing games did not follow the gaming
news. And returning sporadically into the game world I was discovering
that nothing actually has changed. Well, the resolution was higher,
graphics better and explosions more colourful. But the gameplay still
remained the same - defined by Doom at the beginning of 90s. Of the
remarkable events only the release of Nintendo Wii in 2006 comes to
mind, which changed our perception of computer games. They were no
longer something available only to nerds. Now the whole family could
play and, more importantly, while moving rather than sitting
still. Perhaps it was then, when Microsoft saw that and decided
to take the idea to a new level.
Kinect is a small box connected to the Xbox 360. It has 2 cameras that
watch the player, detect the position of his body and movement, and
thereby enable you to control events on the screen. Motion Control in
a pure form – simple and brilliant. No controllers, no wires. According
to Microsoft’s statements, one Kinect can completely digitise
movements of two players and track the positions of four more. The players
may be standing or sitting. In addition, Kinect has multi-array
microphone through which it can recognise the voice of his “master”
and obey his orders.
Microsoft presented Kinect a year ago at E3 exhibition, then it carried
the working title “Project Natal”. And immediately it was clear that
it would be a revolution, if only Microsoft would be able to deliver on
promises. Now, when Kinect is very close to the release, Microsoft has
distributed sample devices to leading gaming magazines. And now we can
say firmly - Microsoft succeeded. According to the lucky ones who
played with Kinect, watching first time the character on the screen
waiving its hands in coordination with you movements is fascinating.
Motion Control is not perfect, but still very good.
This is what a gameplay with Kinect looks like:
I predict that Kinect will be a huge hit. It along with the new Xbox
360 will take the market by storm. Potential customers will have to
stand in a queue for hours to buy it. And for some time after launch
it will not be possible just to walk into a store and buy one, as it is
now impossible to buy an iPhone 4. Neither Sony, nor Nintendo has
So, we are on the eve of the revolution. Now it is the turn of gaming
companies to help us fully explore this bright new world.
As I have already shown you, implicit type conversion is one of the most dangerous features of Oracle SQL and PL/SQL. It is dangerous because it happens automatically without your knowledge and may lead to unpredictable results. These problems are most common when dealing with DATE conversions, but not limited to them.
For example, let’s have a look at this Stackoverflow.com
question by James
James had a problem, the following query was slow:
FROM people a1
WHERE a1.ID LIKE '119%'
AND ROWNUM < 5
A1.ID was indexed, the index wasn’t used and
the explain plan looked like this:
SELECT STATEMENT ALL_ROWS
Cost: 67 Bytes: 2,592 Cardinality: 4 2 COUNT STOPKEY 1 TABLE ACCESS FULL TABLE people
Cost: 67 Bytes: 3,240 Cardinality: 5
James was wondering why.
Well, the key to the issue lies, as it often happens with Oracle, in
an implicit data type conversion. Because Oracle is capable to perform
automatic data conversions in certain cases, it sometimes does that
without you knowing. And as a result, performance may suffer or code
may behave not exactly like you expect.
In our case that happened because
ID column was
LIKE pattern-matching condition expects to see character
types as both left-hand and right-hand operands. When it encounters a
NUMBER, it implicitly converts it to
VARCHAR2. Hence, that query was basically silently rewritten to this:
FROM people a1
WHERE To_Char(a1.ID) LIKE '119%'
AND ROWNUM < 5
That was bad for 2 reasons:
- The conversion was executed for every row, which was slow;
- Because of a function (though implicit) in a
predicate, Oracle was unable to use the index on
If you came across a problem like that, there is a number of
ways to resolve it. Some of the possible options are:
- Create a function-based index on
CREATE INDEX people_idx5 ON people (To_char(ID));
- If you need to match records on first 3 characters of
column, create another column of type
NUMBER containing just these 3
characters and use a plain = operator on it.
- Create a separate column
ID_CHAR of type
VARCHAR2 and fill it with
TO_CHAR(id). Then index it and use instead of
ID in your
- Or, as David Aldridge
pointed out: “It might also be possible to rewrite
the predicate as
ID BETWEEN 1190000 and 1199999, if the values are
all of the same order of magnitude. Or if they’re not then
ID = 119 OR ID BETWEEN 1190 AND 1199, etc.”
Of course if you choose to create an additional column
based on existing ID column, you need to keep those 2 synchronized.
You can do that in batch as a single
UPDATE, or in an
or add that column to the appropriate
UPDATE statements in
James choose to create a function-based index and it worked like a charm.
SYSDATE is one of the most commonly used Oracle functions. Indeed,
whenever you need the current date or time, you just type
you’re done. However, sometimes it’s not all that simple. There are a
few confusions associated with
SYSDATE that are pretty common and, if
not understood, can cause a lot of damage.
First of all,
SYSDATE returns not just current date, but date and time
combined. More precisely, the current date and time down to a second.
If just a date is needed,
TRUNC function has to be applied, that is,
TRUNC(SYSDATE). For a sake of a good database design, date should not be
confused with date/time. For example, if a column in a table is called
transaction_date, it would be natural for it to contain a date,
but not date/time. That may lead to a major confusion. Let’s imagine
there is a table
BANK_TRANSACTIONS containing the following fields:
The last field is of the most interest to us. Apparently its data type
DATE, but is it a date or date/time? We can’t tell by just looking
at the table definition. Nonetheless, it is a very important thing to
know. A common case for using DATE columns is including them in date
range queries. Forexample, if we wanted to get all the bank transactions
from 1 January 2009 to 31 July 2009 we could write this:
WHERE txn_date BETWEEN To_date('01-JAN-2009','DD-MON-YYYY')
And that would be fine if
TXN_DATE were a date column. But if it is
a date/time, we would just have missed a whole day worth of data. And it
is because, as I said,
DATE data type can hold date/time down to a
second. That means that for 31 July 2009 it could hold values ranging
from 0:00am to 11:59pm. But because
TO_DATE('31-JUL-2009', 'DD-MON-YYYY') is basically an equivalent to
TO_DATE('31-JUL-2009 00:00:00', 'DD-MON-YYYY HH24:MI:SS'), all the transactions happened
after 0:00am on 31 July 2009 would be missed out.
That kind of mistake is pretty common. Sometimes it’s hard to tell by
just looking at the data whether a particular
DATE column can have date
portion. Even if all the values in there are rounded to 0:00 hours, that
doesn’t mean that a different time value can’t appear there in the
future. The data dictionary can’t help us here either –
DATE type is
always the same whether it contains time or not. (By the way, Oracle
TIMESTAMP type for new
projects, but that is a whole different story.)
If you are working with an existing table and you are not sure, you can
use a fool-proof method like this:
WHERE txn_date BETWEEN To_date('01-JAN-2009','DD-MON-YYYY')
AND To_date('31-JUL-2009','DD-MON-YYYY') + 1 – 1/24/3600
+1 – 1/24/3600 here means “Plus 1 day minus 1 second”. That is because
DATE type means “1 day”, “1/24” - 1 hour, and there are 3600
seconds in an hour.
The above expression will retrieve all the transactions from “01 January
2009 0:00am” to “31 July 2009 0:00am plus 1 day minus 1 second”, i.e. to
“31 July 2009 23:59pm”.
If you are charged with designing an application and need to create a
table with a
DATE column, it is worth to keep yourself and others from
future confusions by a simple trick: name columns that only contain date
DATE and add
TIME to the name of the columns that
you know will contain time components. In our case it would be prudent
to call the
The second issue I’d like to discuss is much more subtle, but can do
even more damage.
Imagine that you are charged with developing a report that returns all
the transaction for the previous month. It looks like a job for SYSDATE!
You fetch your trusty keyboard and after a few minutes of typing you
come up with something like this:
WHERE txn_date BETWEEN Last_day(Add_months(Trunc(SYSDATE),-2)) + 1
You create a few lines in
BANK_TRANSACTIONS table, run a few unit tests
to make sure your code works and check it into the source control. Job
done! You congratulate yourself on the productive work and spend the
rest of the day reading your friends’ blogs and dreaming about your next
vacation. And the next day you move on to another task and get as busy
After some time, which may be a few days or months, depending on the
pace of the project, the code you wrote gets migrated into the UAT
environment. And a task force of a few testers and end users is assigned
to test the report you wrote. And as it often happens in UAT, they are
going to test in on real data they extracted from the production
system – that is, the last year’s data.
Got it? Last year’s.
The final stages of testing, such as UAT, have to prove that the system
does what it is expected to do in conditions that resemble the
production as closely as possible. And the best way to do that is to
test it on the retrospective production data – the data that is proven.
That makes it possible to compare the outcome to the actual production
system, and thus, prove or disprove that the new system works.
That sounds reasonable. But one of the implications for you is that
BANK_TRANSACTIONS table is not going to contain previous month’s
transactions. Hence, your report will be blank. You can’t rewind back
time because you hard-coded
SYSDATE, which has only one meaning – “right
now”. Test failed.
If you have known that when you wrote it, you wouldn’t have used the
SYSDATE. You would use a parameter, something like
you could set to whatever date you wanted. And that would do. Well, now
You only need a single look at Sydney Opera House to recognise that it
is a work of art. Any masterpiece is like that – you don’t need to do a
throughout examination of Mona Lisa’s smile to realise its beauty – you
see it instantly. Perfection needs no explanation, it works on
The same applies to the software engineering too. Great code always
looks good. It is always carefully formatted, indented and commented. By
just looking at it you can tell that it is a work of art. Such code will
always work, do what it is supposed to do and have a very few bugs.
Because whoever wrote that code cared a lot about it. And you can safely
assume that if anyone has put a lot of effort into making the code
looking good, he has put at least as much effort into designing and
What is even more important, carefully carved code is easier to
maintain. In modern software projects any single procedure gets tweaked
and rewritten tens of times. If you are a programmer, good chances that
even in a project that you work on right now you inherited some code
that was written years ago, maybe from people who long left the company.
And when you finish with it, it will not be the end of the story – the
code will be passed to QA and finally to the production support. And
then the cycle will start again. Hence, whatever you program, it’s not
just about you. You don’t know how many people will be looking into your
code trying to make sense of it. And you can help them immensely by
making it is easy to read and understand now. Whether you will be
remembered as a good programmer or cursed depends on it.
So, you made an effort to write the code that works. Now make an extra
step – make it beautiful.
Those who know me know that I’ve been searching for a perfect ebook
reader device for years. I’ve used mobile phones, Palm PDAs, pocket PCs,
laptops… About 7 years ago I got excited about prospects of
promising to deliver just what I needed. Unfortunately, E-Ink has turned
out to be utter disappointment, so far delivering little but bold
promises. It took years and years for the first E-Ink devices to turn up
on the market.
A few years ago I finally got my hands onto Sony
E-Ink reader. Got disappointed with it after a week and sold it. A year
ago I bought another E-Ink reader - that time
BeBook. I still have it,
but now my wife uses it. And I’ve got myself something better. That is
Don’t get me wrong. I still like E-Ink readers. But even after all those
years E-Ink remains to be a promising technology. Guys, it’s about time
to deliver on promises. Maybe one day… But now, E-Ink has more cons
than pros: devices are expensive, screens are slow, the screen contrast
is poor. And versatility is even poorer - every E-Ink reader is
practically useless for anything but reading, making you carry yet
another device in your bag. And if all those weren’t enough, many
manufacturers lock the devices to just a few supported DRM-enabled book
formats (this is for you, Amazon).
In few short years, iPhone delivered what E-Ink failed in decade. The
truth is, the iPhone’s screen is brilliant. I don’t know how they did
it, but it’s bright, highly contast and it (almost) doesn’t fade in
sunlight. Yes, it’s resolution is not as high as of some VGA PDAs and
laptops, but it still looks better than any other LCD screen I’ve seen.
Reading from that screen is a pleasure. Honestly, if I am provided a
choice to read from either E-Ink (in its current state) and iPhone’s
LCD, I’d probably choose iPhone.
And unlike the dedicated readers, iPhone is immensely versatile. I don’t
know the statistics, but it’s got to be the most popular mobile software
platform out there. Thousands and thousands of software titles are
available. And there is no problems with ebook types either - Software
like Stanza and
Calibre make reading almost
any kind of book a simple task.
All in all, for all of you who has been waiting for a perfect reader -
the wait is almost over. iPhone has delivered yet another revolution.
Now is the time for a major publishing houses to wake up.