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When and why are database joins expensive?
...s back to mitigating the size of the working set. Joins involving properly selected keys with correctly set up indexes are cheap, not expensive, because they allow significant pruning of the result before the rows are materialised.
Materialising the result involves bulk disk reads which are the mo...
How to run a program without an operating system?
...her such weird keys after power-on until you get a boot menu where you can select to boot from the USB.
It is often possible to configure the search order in those menus.
For example, on my T430 I see the following.
After turning on, this is when I have to press Enter to enter the boot menu:
The...
what is Promotional and Feature graphic in Android Market/Play Store?
...s above are now broken but the detailed information can be found here
Selected applications have the ability
to be featured atop their respective
categories. This is not a guaranteed
feature, but uploading promotional
graphics is something that we
recommend.
...
Error: CUICatalog: Invalid asset name supplied: (null), or invalid scale factor : 2.000000
...
In Xcode 6.4, this seems to occur when using "Selected Image" for a tab bar item in the storyboard, even if it's a valid image.
This doesn't actually seem to set the selected state image anyway, so it needs to be defined in User Defined Runtime Attributes, and removed...
gdb fails with “Unable to find Mach task port for process-id” error
...Self Signed Root”, set “Certificate Type” to “Code Signing” and select the “Let me override defaults”. Click “Continue”.
You might want to extend the predefined 365 days period to 3650 days.
Click several times on “Continue” until you get to the “Specify a Location For The Ce...
When to use Preorder, Postorder, and Inorder Binary Search Tree Traversal strategies
... Pre-Order, In-order or Post-Order?
The traversal strategy the programmer selects depends on the specific needs of the algorithm being designed. The goal is speed, so pick the strategy that brings you the nodes you require the fastest.
If you know you need to explore the roots before inspecting ...
Android Studio: how to attach Android SDK sources?
...uild.gradle with the desired API level.
In the Project window on the left, select the External Libraries drop-down.
Right click the menu item and select Open Library Settings.
Click the Sourcepath tab and use the + icon at the bottom left to link to the desired SDK sources (should be in something/s...
Solution to INSTALL_FAILED_INSUFFICIENT_STORAGE error on Android [closed]
...". Locate the "Android Application" node in the tree at the left, and then select your project and go to the "Target" tab on the right side of the window look down for the "Additional Emulator Command Line Options" field (sometimes you'll need to make the window larger) and finally paste "-partition...
Can PostgreSQL index array columns?
... for this test...
SET enable_seqscan TO off;
EXPLAIN ANALYZE
SELECT * FROM "Test" WHERE "Column1" @> ARRAY[20];
Result:
Bitmap Heap Scan on "Test" (cost=4.26..8.27 rows=1 width=32) (actual time=0.014..0.015 rows=2 loops=1)
Recheck Cond: ("Column1" @> '{20}'::integer[])
-&...
How to create a date and time picker in Android? [closed]
.... This Date object contains
// the date and time that the user has selected.
}
@Override
public void onDateTimeCancel()
{
// Overriding onDateTimeCancel() is optional.
}
};
Then you create and show the dialog:
new SlideDateTimePicker.Builder(getSupportFragment...