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Why is SSE scalar sqrt(x) slower than rsqrt(x) * x?
... there are some info, especially about rsqrt (cpu is using internal lookup table with huge approximation, which makes it much simpler to get the result). It may seem, that rsqrt is so much faster than sqrt, that 1 additional mul operation (which isn't to costly) might not change the situation here. ...
Foreign keys in mongo?
...tions/referenced/1-n.html
In a NoSQL database like MongoDB there are not 'tables' but collections. Documents are grouped inside Collections. You can have any kind of document – with any kind of data – in a single collection. Basically, in a NoSQL database it is up to you to decide how to organi...
How to write DataFrame to postgres table?
...te_engine('postgresql://scott:tiger@localhost:5432/mydatabase')
df.to_sql('table_name', engine)
You are correct that in pandas up to version 0.13.1 postgresql was not supported. If you need to use an older version of pandas, here is a patched version of pandas.io.sql: https://gist.github.com/jor...
PostgreSQL naming conventions
Where can I find a detailed manual about PostgreSQL naming conventions? (table names vs. camel case, sequences, primary keys, constraints, indexes, etc...)
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Is an index needed for a primary key in SQLite?
When an integer column is marked as a primary key in an SQLite table, should an index be explicitly created for it as well? SQLite does not appear to automatically create an index for a primary key column, but perhaps it indexes it anyway, given its purpose? (I will be searching on that column all t...
PHP PDO: charset, set names?
...llation by clicking your database and choose operations. If you try create tables with another collation than your database, your tables will end up with the database collation anyways.
So make sure the collation for your database is right before creating tables. Hope this saves someone a few hours...
UITableView load more when scrolling to bottom like Facebook application
...eloping an application that uses SQLite. I want to show a list of users (UITableView) using a paginating mechanism. Could any one please tell me how to load more data in my list when the user scrolls to the end of the list (like on home page on Facebook application)?
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Linear Regression and group by in R
...factor are your variables. Please keep in mind that Your.df must be a data.table class
– FraNut
Nov 17 '15 at 9:33
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What are the options for storing hierarchical data in a relational database? [closed]
...useful for managing hierarchical data:
the HierarchyId data type.
common table expressions, using the with keyword.
Have a look at "Model Your Data Hierarchies With SQL Server 2008" by Kent Tegels on MSDN for starts. See also my own question: Recursive same-table query in SQL Server 2008
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Disable migrations when running unit tests in Django 1.7
...been run, the "migrate" command treats
an app as unmigrated, and creates tables directly from the models just
like syncdb did in 1.6. I defined a new settings module just for unit
tests called "settings_test.py", which imports * from the main
settings module and adds this line:
MIGRATIO...