Re: Operation on bit strings with different length

Arif,

For future notice, the NOVICE list is the appropriate place for this
type of question.

> Do you know how to operate (AND, OR, etc.) on bit strings with
> dynamically different length? It is dynamic, means the length won't
> be
> determined until run time.
> Is there any function to extend the length of a bit string to a
> certain
> length?

PostgreSQL is currently (as far as I know) lacking a good set of bitwise
data types and operators.  If you really need to use them, I suggest
that you construct them -- Postgres allows you to build your own data
types, and operators for those data types.  It's a somewhat
labor-intensive process.

Most of us don't have much use for bitwise operations in the database,
because the essential intent of a bitwise number is to store several
different pieces of data in the same number.  This goes against
relational principles, which say that each field should be "atomic";
that is, containing one and only one piece of information.

If, however, you are interacting with the MS API, I can see why you
would need bitwise logic.  So my suggestions are:

1. Create your own data types and operators per paragraph 1;
2. Just store the integer in Postgres, and do your bitwise logic in your
interface/middleware language.

-Josh Berkus

-Josh Berkus


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