Writing C Functions and

C User Defined Types on Windows

Using Visual Studio (C++)

By Tim Child

November 2010

Biography

• Tim Child • 35 years experience in software development • Formerly

– VP Oracle Corporation – VP BEA Systems Inc. – VP Informix

• 30 + years experience in 3D, CAD, GIS and DBMS

Learn Teach Learn

Lecture 5%

Read 10%

Audio Visual 20%

Demonstration 30%

Discuss in Groups 50%

Practice By Doing 75%

Teach Others – Use of Learning 90%

Source: National Training Institute

Outline

• Outline • Course Topics • UDF’s, UDT’s & UDA • Programming Environment • Worked Examples • Artifacts • Creating VS2010 Projects • Setting Include Files & Directories • Exporting C Functions • Specifying Pre-Processor Macros • Setting Compiler Command Lines • Setting Linker Command Lines and Libraries • Creating and Loading Functions • Testing C Functions • Debugging C Functions • Building C Functions on the Windows x64 Platform • Useful Resources and Other Tools • Wish list • Q&A

Course Topics

• Topics

– C Programming

– SQL

– PostgreSQL Functions

– Visual Studio

– Windows

– Windows Debugging

PostgreSQL UDF’s, UDT’s & UDA’s

• User Defined Functions

– C Functions executing in server

• User Defined Types

– SQL Base types implemented in C

• User Defined Aggregates

– SQL Aggregate implemented in C

PostgreSQL UDT’s & UDA’s Components

UDT

Comprises

• Input Function

– Convert Text to Binary

• Output Function

– Convert Binary to Text

• Optional Functions

UDA

Comprises

• Accumulation Function

– Processes each tuple

• Output Function

– Delivers result

PostgreSQL Server Coding Paradigms

#include “postgres.h”

PG_FUNCTION_INFO_V1 ( Myfunc );

DLLEXPORT Datum Myfunc (PG_FUNCTION_ARGS) { PG_GETARG_xxx( N ); … mytype = (struct mytype*) palloc(sizeof(struct mytype)); … if ( …) elog(ERROR, “ Message “); … PG_RETURN_xxx( … ) }

Header Files

Function Declaration

Parameter Passing

Storage Allocation

Error Handling

Returning Results

Programming Environment

• Windows 7 Laptop

• VS 2010 Ultimate

– VS2010 Express will work

• PostgreSQL 9.0 RC1 (x32)

• PostgreSQL 9.0 RC1 (x64)

• Windows 7 Platform SDK

Worked Examples

• Basic C Function

• C User Defined Type

• User Defined Aggregate

• Array returning functions

Artifacts

• .h file structs, constants, prototypes, … • .c file C function code • SQL file to “install” the functions & types Tip: use extension pgsql not sql • SQL file to “uninstall” the functions & types • SQL file to test the function

Creating Visual Studio Projects

• Choice of 2 types of Project • Makefile

or

• Win32 DLL – No precompiled headers

– Empty project

VS2010 Project Settings

Setting Include Files and Directories

Exporting C Functions Entry Points

#if defined( _WIN32) #define DLLEXPORT __declspec(dllexport) #else #define DLLEXPORT #endif

3 Ways to Export a DLL Entry Point • declspec(dllexport) • .def file • Linker Command

Specifying Pre-Processor Macros

• Useful #defines that will help speed the compiler

#define WIN32_LEAN_AND_MEAN #define NOCOMM

#define WIN32_LEAN_AND_MEAN #define NOCOMM API header files.

NOapi

Setting Compiler Command Line Options

cl.exe /TC /LD /showIncludes file.c /TC Specifies that the source files are to be compiled a C files /LD Create a DLL. /showIncludes Lists the include files. Very useful for debugging include directories issues.

Setting Linker Libraries

Additional Dependencies

Compiling Messages

1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(86): warning C4005: 'EIDRM' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(103) : see previous definition of 'EIDRM' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(247): warning C4005: 'EMSGSIZE' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(107) : see previous definition of 'EMSGSIZE' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(248): warning C4005: 'EAFNOSUPPORT' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(94) : see previous definition of 'EAFNOSUPPORT' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(249): warning C4005: 'EWOULDBLOCK' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(132) : see previous definition of 'EWOULDBLOCK' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(250): warning C4005: 'ECONNRESET' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(100) : see previous definition of 'ECONNRESET' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(251): warning C4005: 'EINPROGRESS' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(104) : see previous definition of 'EINPROGRESS' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(252): warning C4005: 'ENOBUFS' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(111) : see previous definition of 'ENOBUFS' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(253): warning C4005: 'EPROTONOSUPPORT' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(127) : see previous definition of 'EPROTONOSUPPORT' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(254): warning C4005: 'ECONNREFUSED' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(99) : see previous definition of 'ECONNREFUSED' 1>c:\program files (x86)\postgresql\9.0\include\server\pg_config_os.h(256): warning C4005: 'EOPNOTSUPP' : macro redefinition 1> c:\program files (x86)\microsoft visual studio 10.0\vc\include\errno.h(122) : see previous definition of 'EOPNOTSUPP' 1> Generating Code...

• Safe to Ignore these messages

Creating and Loading Functions

• Windows uses back slashes \ for the delimiter in paths between folders. • To use Windows style paths

• Single backslash (\) replaced with a double (\\)

E’ C:\\Program Files (x86)\\PostgreSQL\\8.4\\lib\testfunc.dll’

• Setting up the $libdir variable, allows PostgreSQL to find the DLL's to load libdir=C:\Program Files (x86)\PostgreSQL\8.4\lib CREATE or replace FUNCTION add_one(integer) RETURNS integer AS '$libdir/testfunc1.dll', 'add_one' LANGUAGE C STRICT;

Testing C Functions

• Testing frameworks like pgunit or pgtap

• Use pgAdmin III to Load and Execute the Function

Debugging C Functions

• Copy DLL & PDB file to Lib Directory • Define the function to PostgreSQL

– Using Create Function

• Find the backend Process Id – Select pg_backend_pid();

• Set Breakpoint in VC++ – Check All Processes and All Users – Check Allow source code to be different

• Attach the debugger to the Process – Need to restart VS as admin

• Execute the function from pgAdmin III

Building C Functions on the

Windows x64 Platform • Set VS Configuration Manager Platform

• Build, Copy Debug, Test as before • Harder to find x64 third party Libraries

Useful Resources and Other Tools

• Use Anywhere PE to display DLL Contents

http://www.ucware.com/apev/index.htm

Information Resources

• Contrib Directories

– Many examples of C Functions

• pGFoundry

– More examples of C Functions

• PostgreSQL Doxygen

– Very useful for reverse engineering

VS Tool Box

Drag and Drop Code Snippets

Wish List

Here is a list of things in no particular priority that would help the development of PostgreSQL C Functions on Windows. • A quicker way to unload DLL’s so they can be copied without re-starting the server.

• Visual Studio Template Project for building C Function DLL’s

• A Visual Studio PostgreSQL syntax checker. Intelli-sense provides great value but

wants to syntax check SQL files against SQL Server syntax.

• A Visual Studio Add-in to execute SQL queries directly from the VS Tool. • Most radically, implement functions in the CLR language.

Q&A

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