I want to create a database of images, the table is like this:
I created a GUI application that displays an image from a webcam,Code:+--------------+ | user_image | +--------------+ | id (integer) | | img (oid) | +--------------+
so when I push the button the display will freeze and the app will
insert the image data to the database and the id will be
incremented automatically (id starts at 0).
how can I insert the data?
You should just set id to the PostgreSQL equivalent of INTEGER PRIMARY KEY AUTOINCREMENT -- and id will start at 1 not 0.Originally Posted by cph
You could write the image to a file and put the filepath into the db rather than the image itself.
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
3 (different) GNU debugger tutorials: #1 -- #2 -- #3
cpwiki -- our wiki on sourceforge
Just use bigserial as the column type for your primary key. bigserial types are incremented automatically, so you don't need to adjust them. Just do:
INSERT INTO user_image (img) VALUES (img_value);
The id will be inserted for you.
I've tried to write something like this
it compiles fine, but when I try to execute it, an error occurred.Code:#include <libpq-fe.h> #include <libpq/libpq-fs.h> #include <stdio.h> int main (void) { Oid lobjId; PGconn *conn = PQsetdb(NULL, NULL, NULL, NULL, "cpns"); if (conn != NULL) { PGresult *result = PQexec(conn, "begin"); PQclear(result); lobjId = lo_creat(conn, INV_WRITE | INV_READ); if (lobjId == 0) { printf("Unable to create large object\n"); } else { printf("Large object successfully created\n"); } PQexec(conn, "end"); PQfinish(conn); } return(0); }
what's wrong with it?
Please be a little more specific. What error?it compiles fine, but when I try to execute it, an error occurred.
I'm sorry, actually it crashes immediately.
What did it hit?I'm sorry, actually it crashes immediately.
So by "crash" you mean seg fault, or making a sudden loud noise?
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
3 (different) GNU debugger tutorials: #1 -- #2 -- #3
cpwiki -- our wiki on sourceforge
a seg fault
>> actually it crashes immediately
I've never used this API before, but one thing I noticed is that you aren't checking to see if 'result' is NULL.
Code:#include <cmath> #include <complex> bool euler_flip(bool value) { return std::pow ( std::complex<float>(std::exp(1.0)), std::complex<float>(0, 1) * std::complex<float>(std::atan(1.0) *(1 << (value + 2))) ).real() < 0; }
One more thing, it looks like the proper way to check the return value of PQsetdb is:
Code:if (PQstatus(conn) != CONNECTION_BAD)
Code:#include <cmath> #include <complex> bool euler_flip(bool value) { return std::pow ( std::complex<float>(std::exp(1.0)), std::complex<float>(0, 1) * std::complex<float>(std::atan(1.0) *(1 << (value + 2))) ).real() < 0; }
I've modified the source code to check the return value, but it's still not working
well, I guess I can't insert the actual image data
