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How do you delete an ActiveRecord object?
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It's destroy and destroy_all methods, like
user.destroy
User.find(15).destroy
User.destroy(15)
User.where(age: 20).destroy_all
User.destroy_all(age: 20)
Alternatively you can use delete and delete_all which won't enforce :before_destroy and :after...
Update MongoDB field using value of another field
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The best way to do this is in version 4.2+ which allows using of aggregation pipeline in the update document and the updateOne, updateMany or update collection method. Note that the latter has been deprecated in most if not all languages drivers.
MongoDB 4.2+
Version 4.2 ...
Removing Data From ElasticSearch
...lasticSearch. I have deleted my indexes. However, that doesn't seem to actually remove the data itself. The other stuff I've seen points to the Delete by Query feature. However, I'm not even sure what to query on. I know my indexes. Essentially, I'd like to figure out how to do a
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Any implementation of Ordered Set in Java?
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Take a look at LinkedHashSet class
From Java doc:
Hash table and linked list implementation of the Set interface, with predictable iteration order. This implementation differs from HashSet in that it maintains a doubly-linked list running through all of its entries. This linked l...
libpthread.so.0: error adding symbols: DSO missing from command line
...nd line after the object files being compiled:
gcc -Wstrict-prototypes -Wall -Wno-sign-compare -Wpointer-arith -Wdeclaration-after-statement -Wformat-security -Wswitch-enum -Wunused-parameter -Wstrict-aliasing -Wbad-function-cast -Wcast-align -Wstrict-prototypes -Wold-style-definition -Wmissing-pr...
How to make an OpenGL rendering context with transparent background?
Rendering contexts usually have a solid color on the background (black or whatever, see the image below):
9 Answers
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How can I use threading in Python?
...ticle/blog post that you should definitely check out (no affiliation) - Parallelism in one line: A Better Model for Day to Day Threading Tasks. I'll summarize below - it ends up being just a few lines of code:
from multiprocessing.dummy import Pool as ThreadPool
pool = ThreadPool(4)
results = pool.m...
Python ElementTree module: How to ignore the namespace of XML files to locate matching element when
I want to use the method of "findall" to locate some elements of the source xml file in the ElementTree module.
10 Answers
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Node.js / Express.js - How does app.router work?
...use is app.use() . When the middleware is being executed, it will either call the next middleware by using next() or make it so no more middleware get called. That means that the order in which I place my middleware calls is important, because some middleware depends on other middleware, and some...
MySQL - Get row number on select
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Swamibebop's solution works, but by taking advantage of table.* syntax, we can avoid repeating the column names of the inner select and get a simpler/shorter result:
SELECT @r := @r+1 ,
z.*
FROM(/* your original select statement goes in here */)z,
(SELECT @r:=0)y;
So ...