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Grouped LIMIT in PostgreSQL: show the first N rows for each group?
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Since v9.3 you can do a lateral join
select distinct t_outer.section_id, t_top.id, t_top.name from t t_outer
join lateral (
select * from t t_inner
where t_inner.section_id = t_outer.section_id
order by t_inner.name
limit 2...
Can git automatically switch between spaces and tabs?
...l'
All systems
You may now check out all the files of your project. You can do that with:
git checkout HEAD -- **
and all the python files will now have tabs instead of spaces.
Edit: changed the forced checkout command. You should commit your work first, of course.
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How update the _id of one MongoDB Document?
...f one document. I know it's not a really good pratice. But with some technical reason, I need update it. If I try to update it I get:
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What exactly is Python's file.flush() doing?
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There's typically two levels of buffering involved:
Internal buffers
Operating system buffers
The internal buffers are buffers created by the runtime/library/language that you're programming against and is meant to speed things up by...
Purpose of ESI & EDI registers?
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There are a few operations you can only do with DI/SI (or their extended counterparts, if you didn't learn ASM in 1985). Among these are
REP STOSB
REP MOVSB
REP SCASB
Which are, respectively, operations for repeated (= mass) storing, loading and scannin...
B-Tree vs Hash Table
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You can only access elements by their primary key in a hashtable.
This is faster than with a tree algorithm (O(1) instead of log(n)), but you cannot select ranges (everything in between x and y).
Tree algorithms support this in L...
Output array to CSV in Ruby
It's easy enough to read a CSV file into an array with Ruby but I can't find any good documentation on how to write an array into a CSV file. Can anyone tell me how to do this?
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Putting text in top left corner of matplotlib plot
How can I put text in the top left (or top right) corner of a matplotlib figure, e.g. where a top left legend would be, or on top of the plot but in the top left corner? E.g. if it's a plt.scatter(), then something that would be within the square of the scatter, put in the top left most corner.
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How to track down log4net problems
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First you have to set this value on the application configuration file:
<configuration>
<appSettings>
<add key="log4net.Internal.Debug" value="true"/>
</appSettings>
</configuration>
Then, to determine the file in which you w...
Chrome: timeouts/interval suspended in background tabs?
...cted) setTimeout is not very accurate but for most appliances not dramatically inaccurate. Now if I run the test in in Chrome and let it run in a background tab (so, switching to another tab and browse on there), returning to the test and inspecting te results (if the test finished) they are drama...