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String's Maximum length in Java - calling length() method
..., which is 2^31 - 1 (or approximately 2 billion.)
In terms of lengths and indexing of arrays, (such as char[], which is probably the way the internal data representation is implemented for Strings), Chapter 10: Arrays of The Java Language Specification, Java SE 7 Edition says the following:
The...
schema builder laravel migrations unique on two columns
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The second param is to manually set the name of the unique index. Use an array as the first param to create a unique key across multiple columns.
$table->unique(array('mytext', 'user_id'));
or (a little neater)
$table->unique(['mytext', 'user_id']);
...
Git file permissions on Windows
...ing command adds user execute permission to an arbitrary file:
git update-index --chmod=+x <file>
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How to represent empty char in Java Character class
... main(String[] args) throws Exception {
String s = "abcdefg";
int index = s.indexOf('d');
// delete a char from a char[]
char[] array = s.toCharArray();
char[] tmp = new char[array.length-1];
System.arraycopy(array, 0, tmp, 0, index);
System.arraycopy(array, index+1, tm...
Pandas DataFrame Groupby two columns and get counts
...e your second question:
In [56]: df.groupby(['col5','col2']).size().reset_index().groupby('col2')[[0]].max()
Out[56]:
0
col2
A 3
B 2
C 1
D 3
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Find size of an array in Perl
...dard way to get an array's size.
The second way actually returns the last index of the array, which is not (usually) the same as the array size.
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How to convert SQL Query result to PANDAS Data Structure?
... way to do it, as you don't need to manually use .keys() to get the column index. Probably Daniel's answer was written before this method existed. You can also use pandas.io.sql.read_frame()
– RobinL
Oct 13 '13 at 13:54
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How do I modify fields inside the new PostgreSQL JSON datatype?
... create_missing boolean default true)
path can contain JSON array indexes too & negative integers that appear there count from the end of JSON arrays. However, a non-existing, but positive JSON array index will append the element to the end of the array:
SELECT jsonb_set('{"a":[null,{"b...
How to find and return a duplicate value in array
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Simply find the first instance where the index of the object (counting from the left) does not equal the index of the object (counting from the right).
arr.detect {|e| arr.rindex(e) != arr.index(e) }
If there are no duplicates, the return value will be nil.
I be...
MySQL order by before group by
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For scaling, the compound INDEX(post_author, post_date) is important.
– Rick James
Mar 1 '15 at 16:08
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