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What is the purpose of setting a key in data.table?
... "cold" by
require(data.table)
DT <- data.table(x=rep(1:5, each=2), y=1:10)
DT[, mean(y), by=x] # no key is set, order of groups preserved in result
However, prior to v1.9.6, joins of the form x[i] required key to be set on x. With the new on= argument from v1.9.6+, this is not true anymore, an...
When to use Comparable and Comparator
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answered Feb 15 '10 at 15:18
YishaiYishai
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Limiting the number of records from mysqldump?
...s skaffman says, use the --where option:
mysqldump --opt --where="1 limit 1000000" database
Of course, that would give you the first million rows from every table.
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How can I count the occurrences of a list item?
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answered Apr 8 '10 at 13:31
ŁukaszŁukasz
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Is git-svn dcommit after merging in git dangerous?
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answered Nov 21 '10 at 15:05
Sebastien VarretteSebastien Varrette
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What does LINQ return when the results are empty
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leppieleppie
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How to cache data in a MVC application
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answered Dec 5 '08 at 14:10
terjetylterjetyl
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What's quicker and better to determine if an array key exists in PHP?
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GraphViz - How to connect subgraphs?
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answered Jan 6 '10 at 10:03
High Performance MarkHigh Performance Mark
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Git - deleted some files locally, how do I get them from a remote repository
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answered Nov 20 '10 at 23:20
CascabelCascabel
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