README - How to use

Important notes:

Please consider the recommendations for c functions in postgres sql: http://www.postgresql.org/docs/8.2/static/xfunc-c.html

Recomendations:

1 - When including C codes always wrap the code with extern "C".

2 - Return variables always have to be dynamically allocated with palloc() (not malloc()) previous to the end of execution of the function, otherwise these values are gonna be lost.

3 - When making your own dynamic library (.so or .dll) It is easier to set the enviroment using an IDE. I personally find making a Makefile by hand hard, since you have to include dynamic libraries path, e.g. OpenCV. An example of including dynamic libraries can be seen in: https://www.youtube.com/watch?v=UFsJ4P5QYKQ

Makefile example:

g++ -shared -c -g -I/usr/local/include/opencv2 -I/usr/include/postgresql/9.4/server -fPIC -MMD -MP -MF "build/Debug/GNU-Linux-x86/cplusplus_functions.o.d" -o build/Debug/GNU-Linux-x86/cplusplus_functions.o cplusplus_functions.cpp mkdir -p build/Debug/GNU-Linux-x86 rm -f "build/Debug/GNU-Linux-x86/my_postgres_functions.o.d" g++ -shared -c -g -I/usr/local/include/opencv2 -I/usr/include/postgresql/9.4/server -fPIC -MMD -MP -MF "build/Debug/GNU-Linux-x86/my_postgres_functions.o.d" -o build/Debug/GNU-Linux-x86/my_postgres_functions.o my_postgres_functions.cpp mkdir -p build/Debug/GNU-Linux-x86 rm -f "build/Debug/GNU-Linux-x86/util_converters.o.d" g++ -shared -c -g -I/usr/local/include/opencv2 -I/usr/include/postgresql/9.4/server -fPIC -MMD -MP -MF "build/Debug/GNU-Linux-x86/util_converters.o.d" -o build/Debug/GNU-Linux-x86/util_converters.o util_converters.cpp mkdir -p dist/Debug/GNU-Linux-x86 g++ -shared -o dist/Debug/GNU-Linux-x86/libexampleso.so build/Debug/GNU-Linux-x86/cplusplus_functions.o build/Debug/GNU-Linux-x86/my_postgres_functions.o build/Debug/GNU-Linux-x86/util_converters.o -lopencv_calib3d -lopencv_core -lopencv_features2d -lopencv_flann -lopencv_hal -lopencv_highgui -lopencv_imgcodecs -lopencv_imgproc -lopencv_ml -lopencv_objdetect -lopencv_photo -lopencv_shape -lopencv_stitching -lopencv_superres -lopencv_ts -lopencv_video -lopencv_videoio -lopencv_videostab -shared -fPIC

Postgres Examples:

CREATE OR REPLACE FUNCTION get_imgsize(bytea) RETURNS bytea AS '/home/jonathan/NetBeansProjects/exampleso/dist/Debug/GNU-Linux-x86/libexampleso.so', 'get_imgsize' LANGUAGE c IMMUTABLE STRICT COST 1; ALTER FUNCTION get_imgsize(bytea) OWNER TO postgres;

SELECT get_imgsize((SELECT imagem FROM imagem WHERE id = '1'))

CREATE OR REPLACE FUNCTION canny_detector(bytea) RETURNS bytea AS '/home/jonathan/NetBeansProjects/exampleso/dist/Debug/GNU-Linux-x86/libexampleso.so', 'canny_detector' LANGUAGE c IMMUTABLE STRICT COST 1; ALTER FUNCTION canny_detector(bytea) OWNER TO postgres;

SELECT canny_detector(imagem) FROM imagem WHERE id = '2'