Postgres dllimport like SQL Server

Question

Is there any similar thing like SQL Server's UDF (where a function can be exported in a DLL and imported as a function in SQL Server) in Postgres?

For example the function I want to import has the following signature:

public static extern double* svd(double[] a, int d);

the Dll import looks like this:

[DllImport("D:\\my.dll", EntryPoint = "mydll")]

possible duplicate of Call .NET function in external DLL from postgres — ta.speot.is
– ta.speot.is, Commented Feb 4, 2012 at 0:08
Are you trying to write a UDF in C# and use it in T-SQL code? If so, look at CLR Integration: msdn.microsoft.com/en-us/library/ms254498(v=vs.80).aspx — Sebastian Meine
– Sebastian Meine, Commented Feb 4, 2012 at 0:18
This is not at all what the questioner wants. He wants to import a DLL into Postgres. — codekaizen
– codekaizen, Commented Feb 4, 2012 at 0:22
Yes what happens here is that i have a c code that is in a dll and in c# I am calling the extern functions, and finally I use the c# udf as an stored procedure, but I do not know what would be the approach in Postgres... — edgarmtze
– edgarmtze, Commented Feb 4, 2012 at 0:24

codekaizen · Accepted Answer · 2012-02-04 00:34:46Z

0

You can use the Create Function in Postgres:

CREATE FUNCTION svd(double*, int) RETURNS double*
AS 'c:/path/mydll.dll'
LANGUAGE 'C';

More info: http://www.postgresql.org/docs/current/static/xfunc-c.html

You'll likely need to use composite types since it appears you're manipulating matricies with variable numbers of rows and columns.

edited Feb 4, 2012 at 0:34

answered Feb 4, 2012 at 0:28

codekaizen

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2 Comments

edgarmtze Over a year ago

Yes I am manipulating matrices, about the composite types can you give a little more detail?

Craig Ringer Over a year ago

@cMinor You can represent an n-dimensional matrix using an n-dimensional PostgreSQL array, so you won't have to implement your own data types. Just write a C function that accepts a double[][] array and returns another double[][] then map it into SQL using "CREATE FUNCTION". Read the PostgreSQL sources for examples - look up functions that take and/or return n-dimensional arrays and look at their C implementations. The documentation covers the basics of C functions well.

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