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Fast permutation -> number -> permutation mapping algorithms
... brought down to n*log(n), see section 10.1.1
("The Lehmer code (inversion table)", p.232ff) of the fxtbook:
http://www.jjj.de/fxt/#fxtbook
skip to section 10.1.1.1 ("Computation with large arrays" p.235) for the fast method.
The (GPLed, C++) code is on the same web page.
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Reset the database (purge all), then seed a database
Is there a rake command to wipe out the data in the database tables?
6 Answers
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How do I create a unique constraint that also allows nulls?
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This very problem hits ADO.NET DataTables too. So even that I can allow nulls in the backing field using this method, the DataTable won't let me store NULLs in a unique column in the first place. If anyone knows a solution for that, please post it here
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What are some (concrete) use-cases for metaclasses?
... About the ORM case, are you talking about the class-based way of defining tables, or the metaclasses on mapped objects. Because SQLAlchemy can (rightly) map to any class (and I am assuming that it doesn't use a metaclass for that activity).
– Ali Afshar
Dec 24...
How do I remove diacritics (accents) from a string in .NET?
...e limiting yourself to French, you could probably get away with the simple table-based approach in How to remove accents and tilde in a C++ std::string, as recommended by @David Dibben.
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What's the difference between VARCHAR and CHAR?
...: when Anon. says "your content is a fixed size" it means the rows of your table must contain all fixed size fields. You get no performance improvement if you use CHAR against VARCHAR in one field, but the table contains other fields that are VARCHAR.
– Marco Demaio
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NOT IN vs NOT EXISTS
...OT IN sub query were to return no results at all (i.e. the [Order Details] table is empty). In which case it should. In the plan for my sample data this is implemented by adding another anti semi join as below.
The effect of this is shown in the blog post already linked by Buckley. In the example...
How to remove/ignore :hover css style on touch devices
...e the :hover CSS does not make sense, and it can even be disturbing if a tablet triggers it on click/tap because then it might stick until the element loses focus. To be honest, I don't know why touch devices feel the need to trigger :hover in first place - but this is reality, so this problem i...
How to annotate MYSQL autoincrement field with JPA annotations
...he object Operator into MySQL DB.
Prior to save, I try to select from this table and it works, so is connection to db.
10 A...
Declaring a default constraint when creating a table
I am creating a new table in Microsoft SQL server 2000 by writing the code instead of using the GUI, I am trying to learn how to do it "the manual way".
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