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Index on multiple columns in Ruby on Rails
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The order does matter in indexing.
Put the most selective field first, i.e. the field that narrows down the number of rows fastest.
The index will only be used insofar as you use its columns in sequence starting at the beginning. i.e. if you index on [:user_id, :article_id...
reformat in vim for a nice column layout
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Great tip! Just adding, it works for visual selection too with :'<,'>!column -t
– freitass
Aug 23 '12 at 13:16
2
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How to assign multiple classes to an HTML container? [closed]
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Using the Underscore module with Node.js
I've been learning about node.js and modules, and can't seem to get the Underscore library to work properly... it seems that the first time I use a function from Underscore, it overwrites the _ object with the result of my function call. Anyone know what's going on? For example, here is a session ...
Mockito: InvalidUseOfMatchersException
...othing().when(cmd).dnsCheck(HOST, any(InetAddressFactory.class))
uses one raw value and one matcher, when it's required to use either all raw values or all matchers. A correct version might read
doNothing().when(cmd).dnsCheck(eq(HOST), any(InetAddressFactory.class))
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Is SQL syntax case sensitive?
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The SQL Keywords are case-insensitive (SELECT, FROM, WHERE, etc), but are often written in all caps. However in some setups table and column names are case-sensitive. MySQL has a configuration option to enable/disable it. Usually case-sensitive table and column na...
How to make a great R reproducible example
... X73 Class
1 A 266 960 Yes
2 A 373 315 No Notice the selection split
3 A 573 208 No (which can be turned off)
4 A 907 850 Yes
5 B 202 46 Yes
6 B 895 969 Yes <~~~ 70 % of selection is from the top rows
7 B 940 928 No
98 Y 37...
How to split a long regular expression into multiple lines in JavaScript?
...(() => {
const createRegExp = (str, opts) =>
new RegExp(str.raw[0].replace(/\s/gm, ""), opts || "");
const yourRE = createRegExp`
^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|
(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|
(([a-...
Is git's semi-secret empty tree object reliable, and why is there not a symbolic name for it?
...c642cb6eb9a060e54bf8d69288fbee4904, the empty tree SHA1.
git log --pretty=raw
commit 9ed4ff9ac204f20f826ddacc3f85ef7186d6cc14
tree 4b825dc642cb6eb9a060e54bf8d69288fbee4904 <====
author VonC <vonc@laposte.net> 1381232247 +0200
committer VonC <vonc@laposte.net> 1381232247 +0200
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jQuery attr vs prop?
...ns (<1.6), we just had attr. To get to DOM properties such as nodeName, selectedIndex, or defaultValue you had to do something like:
var elem = $("#foo")[0];
if ( elem ) {
index = elem.selectedIndex;
}
That sucked, so prop was added:
index = $("#foo").prop("selectedIndex");
This was great, bu...