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JPA EntityManager: Why use persist() over merge()?
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I noticed that when I used em.merge, I got a SELECT statement for every INSERT, even when there was no field that JPA was generating for me--the primary key field was a UUID that I set myself. I switched to em.persist(myEntityObject) and got just INSERT statements then...
PostgreSQL wildcard LIKE for any of a list of words
... can use Postgres' SIMILAR TO operator which supports alternations, i.e.
select * from table where lower(value) similar to '%(foo|bar|baz)%';
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Why does PostgreSQL perform sequential scan on indexed column?
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If the SELECT returns more than approximately 5-10% of all rows in the table, a sequential scan is much faster than an index scan.
This is because an index scan requires several IO operations for each row (look up the row in the ...
How to disable HTML button using JavaScript?
...erence to the element collected through whatever means you like (e.g. querySelector)
– Quentin
Jun 27 '16 at 21:04
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How to become an OpenCart guru? [closed]
...n the theme folder. Should any template not be available for the currently selected theme, the default folder's template is used instead as a fallback. This means themes can be created with very few files and still function fully. It also reduces code duplication and issues as upgrades are made
U...
Given a URL to a text file, what is the simplest way to read the contents of the text file?
... = urllib2.urlopen("http://www.google.com").read(20000) # read only 20 000 chars
data = data.split("\n") # then split it into lines
for line in data:
print line
* Second example in Python 3:
import urllib.request # the lib that handles the url stuff
for line in urllib.request.urlopen(t...
Grabbing the href attribute of an A element
...matches <a at the begining of the string, followed by any number of any char (non greedy) .*? then href= followed by the link surrounded by either " or '
$str = '<a title="this" href="that">what?</a>';
preg_match('/^<a.*?href=(["\'])(.*?)\1.*$/', $str, $m);
var_dump($m);
Output:...
Delete empty lines using sed
...\s*$ will match all "empty" lines, empty here means, the line contains no chars, or the line contains only empty strings (E.g. spaces). All matched lines will be removed by sed, with the d command.
– Kent
Feb 26 '17 at 19:41
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HTML5 Canvas vs. SVG vs. div
...ample, let's say I want to create a rectangle, circle and polygon and then select those objects and move them around.
8 Ans...
Jump to function definition in vim
... mentioned you have to use ctags.
You could also consider using plugins to select appropriate one or to preview the definition of the function under cursor.
Without plugins you will have a headache trying to select one of the hundreds overloaded 'doAction' methods as built in ctags support doesn't ...