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MongoDB/NoSQL: Keeping Document Change History
... changes to one or more specific entities in a database. I've heard this called row versioning, a log table or a history table (I'm sure there are other names for it). There are a number of ways to approach it in an RDBMS--you can write all changes from all source tables to a single table (more of...
Update multiple rows in same query using PostgreSQL
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This is wrong... You will update all rows, even if it is not '123' nor '345'. You should use WHERE column_b IN ('123','456')...
– MatheusOl
Sep 14 '13 at 3:54
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How do I access command line arguments in Python?
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Python tutorial explains it:
import sys
print(sys.argv)
More specifically, if you run python example.py one two three:
>>> import sys
>>> print(sys.argv)
['example.py', 'one', 'two', 'three']
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Loop through properties in JavaScript object with Lodash
.../lodash.com/docs#forOwn
Note that forOwn checks hasOwnProperty, as you usually need to do when looping over an object's properties. forIn does not do this check.
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How to get object length [duplicate]
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This is actually worse than using a simple loop and counter because of the added overhead of the callback function.
– nullability
Feb 19 '13 at 17:35
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Coding Practices which enable the compiler/optimizer to make a faster program
...act.
Expect to be disappointed and to have to work very hard indeed for small performance improvements. Modern compilers for mature languages such as Fortran and C are very, very good. If you read an account of a 'trick' to get better performance out of code, bear in mind that the compiler writer...
mongo group query how to keep fields
...are accumulated/funneled/reduced) doesn't make so much sense even theoretically. However, sorting before hand is actually inefficient compared to sorting each group within themselves since sorting algorithms are more complex than O(n). I wish there would be better ways in MongoDB.
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Saving a Numpy array as an image
... Remember to scale the values to the right range for PNG, usually 0..255. The value ranges in neural networks are frequently 0..1 or -1..1.
– Tomáš Gavenčiak
Mar 31 '18 at 18:49
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MongoDB Many-to-Many Association
... user document:
{name:"Joe"
,roles:["Admin","User","Engineer"]
}
To get all the Engineers, use:
db.things.find( { roles : "Engineer" } );
If you want to maintain the roles in separate documents then you can include the document's _id in the roles array instead of the name:
{name:"Joe"
,roles:...
Getting Java version at runtime
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Wow, that kind of blew my mind. Though in my case, all I wanted was the first two parts of the version so: Runtime.class.getPackage().getSpecificationVersion()
– Wesley Hartford
Dec 10 '14 at 21:44
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