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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...
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Disabling of EditText in Android

... the temporary highlight when touching this view. This also prevents the "select all" popup from appearing. – CzarMatt Jul 6 at 3:33 add a comment  |  ...
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Manually put files to Android emulator SD card

... Card through the Android Perspective (it is called DDMS in Eclipse). Just select the Emulator in the left part of the screen and then choose the File Explorer tab. Above the list with your files should be two symbols, one with an arrow pointing at a phone, clicking this will allow you to choose a f...
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Failed to build gem native extension (installing Compass)

...l the Xcode Command Line Tools this is the key to install Compass. xcode-select --install Installing the Xcode Command Line Tools are the key to getting Compass working on OS X 3. Install Compass sudo gem install compass ...
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Peak detection in a 2D array

...\n" Output without overlapping squares. It seems that the same areas are selected as in your example. Some comments The tricky part is to calculate sums of all 2x2 squares. I assumed you need all of them, so there might be some overlapping. I used slices to cut the first/last columns and rows fr...
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“Unable to find manifest signing certificate in the certificate store” - even when add new key

...t click on your project click on properties usually on the left-hand side, select the "Signing" tab check off the Sign the ClickOnce manifests Make sure you save! share | improve this answer ...
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How to comment out a block of code in Python [duplicate]

... vim with nerdcommenter. Select the block you want and ,c<space> – dev_nut Oct 10 '14 at 22:37 add a comment ...
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How to perform .Max() on a property of all objects in a collection and return the object with maximu

...c T MaxObject<T,U>(this IEnumerable<T> source, Func<T,U> selector) where U : IComparable<U> { if (source == null) throw new ArgumentNullException("source"); bool first = true; T maxObj = default(T); U maxKey = default(U); foreach (var ...
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How to change checkbox's border style in CSS?

... outline is very good, and it works for all input and select boxes, making this useful for ".error" classes. – SztupY Oct 3 '11 at 14:42 2 ...
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Delete all the queues from RabbitMQ?

...oto Policies tab(on the right side) Add Policy Fill Fields Virtual Host: Select Name: Expire All Policies(Delete Later) Pattern: .* Apply to: Queues Definition: expires with value 1 (change type from String to Number) Save Checkout Queues tab again All Queues must be deleted And don't forget remo...