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Does a UNIQUE constraint automatically create an INDEX on the field(s)?
...email, user_id) is enough, you don't need a separate index on email only - MySQL can use leftmost parts of a composite index. There may be some border cases where the size of an index can slow down your queries, but you should not worry about them until you actually run into them.
As for testing in...
Does Foreign Key improve query performance?
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foreign keys do improve performance, at least in MySQL. Moreover, you're right, the creation of a FK does not create an index; the creation of a FK requires an index
– Félix Gagnon-Grenier
Aug 26 '14 at 17:31
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Can you configure log4net in code instead of using a config file?
...e;
roller.ActivateOptions();
hierarchy.Root.AddAppender(roller);
MemoryAppender memory = new MemoryAppender();
memory.ActivateOptions();
hierarchy.Root.AddAppender(memory);
hierarchy.Root.Level = Level.Info;
...
IntelliJ does not show 'Class' when we right click and select 'New'
...
The directory or one of the parent directories must be marked as Source Root (In this case, it appears in blue).
If this is not the case, right click your root source directory -> Mark As -> Source Root.
share
...
How to ignore xargs commands if stdin input is empty?
...t;#args>, -i, and -I <string>:
ls /empty_dir/ | xargs -n10 chown root # chown executed every 10 args or fewer
ls /empty_dir/ | xargs -L10 chown root # chown executed every 10 lines or fewer
ls /empty_dir/ | xargs -i cp {} {}.bak # every {} is replaced with the args from one input line
ls /...
How do I get an apk file from an Android device?
...missions to access the directory your file is in. If not, you will need to root the device first.
If you find that many of the APKs are named "base.apk" you can also use this one line command to pull all the APKs off a phone you can access while renaming any "base.apk" names to the package name. ...
How to pass arguments to a Button command in Tkinter?
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Example GUI:
Let's say I have the GUI:
import tkinter as tk
root = tk.Tk()
btn = tk.Button(root, text="Press")
btn.pack()
root.mainloop()
What Happens When a Button Is Pressed
See that when btn is pressed it calls its own function which is very similar to button_press_handle in t...
Very simple log4j2 XML configuration file using Console and File appender
... </File>
</Appenders>
<Loggers>
<Root level="debug">
<AppenderRef ref="Console" />
<AppenderRef ref="MyFile"/>
</Root>
</Loggers>
</Configuration>
Notes:
Put the following content in yo...
Database Structure for Tree Data Structure
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Have a look at Managing Hierarchical Data in MySQL. It discusses two approaches for storing and managing hierarchical (tree-like) data in a relational database.
The first approach is the adjacency list model, which is what you essentially describe: having a foreign key...
Why all the Active Record hate? [closed]
...database itself, tables, relations, even some logic if the DBMS allows it (MySQL is also grown-up now)
A2) very often, there is more than a data store: file system (blobs in database are not always a good decision...), legacy systems (imagine yourself "how" they will be accessed, many varieties pos...