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Fastest way to count exact number of rows in a very large table?
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@zerkmsby: For COUNT(key) I meant COUNT(primarykey) which should be non nullable. I'll clarify
– gbn
May 20 '11 at 8:30
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How to sort an ArrayList?
...t), using the reverse order comparator makes sure that the sort is stable (meaning that the order of elements will not be changed when they are equal according to the comparator, whereas reversing will change the order).
– Marco13
Aug 30 '14 at 23:18
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How can you dynamically create variables via a while loop? [duplicate]
...bles dynamically via a while loop in Python. Does anyone have any creative means of doing this?
8 Answers
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How to avoid reverse engineering of an APK file?
...Charlie four times and John four times. On the server, interpret what they mean and add it up. This prevents a hacker from sending arbitrary values to your server, as they do not know what word corresponds to what value. As an added measure of security, you could have an equation similar to point 3 ...
Reasons for using the set.seed function
...ccusations of doing this it is best to choose a seed that has some obvious meaning, either always the same seed, or the date, or I use char2seed and the last name of the principle investigator on a project.
– Greg Snow
Dec 6 '12 at 22:28
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What is the difference between partitioning and bucketing a table in Hive ?
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SORTED BY is meant to be used with DISTRIBUTED BY. For instance, you may want to distributed by user id and sort by time within the bucket. CLUSTER BY is just a shortcut for when the clause on the SORTED BY and DISTRIBUTED BY are the sam...
Overlaying histograms with ggplot2 in R
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geom_density(alpha=0.3, fill="red") +
geom_vline(aes(xintercept=mean(eval(parse(text=feature)))), color="black", linetype="dashed", size=1) +
labs(x=feature, y = "Density")
print(plt)
}
Multiple histogram:
plot_multi_histogram <- function(df, feature, label_column) {
plt...
Explicit vs implicit SQL joins
...table2 has about 1000 rows.
This is a very simple case; it doesn't by any means prove that the query optimizer wouldn't get confused and generate different plans in a more complicated case.
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Compare object instances for equality by their attributes
...g __eq__ will automatically make instances of your class unhashable, which means they can't be stored in sets and dicts. If you're not modelling an immutable type (i.e. if the attributes foo and bar may change value within the lifetime of your object), then it's recommend to just leave your instance...
SQLite UPSERT / UPDATE OR INSERT
...esides, I created the table with the clause ON DELETE CASCADE, which would mean that it'd delete data silently. Dangerous.
So, I first thought of a IF clause, but SQLite only has CASE. And this CASE can't be used (or at least I did not manage it) to perform one UPDATE query if EXISTS(select id from ...