PostgreSQL, Second Edition

Client 2—Adding Error Checking

Now let's move on to see how you can detect and respond to errors. When you create an application that works by calling API functions, you can usually tell whether an operation succeeded or failed by examining the return value. In an ecpg application, your program is not calling PostgreSQL functions (at least at the source code level), so you can't just examine a return code.

The sqlca Structure

Instead, the ecpg library uses a special data structure, the sqlca, to communicate failure conditions. Here is the definition of the sqlca structure (from sqlca.h):

 struct sqlca { char sqlcaid[8]; long sqlabc; long sqlcode; struct { int sqlerrml; char sqlerrmc[SQLERRMC_LEN]; } sqlerrm; char sqlerrp[8]; long sqlerrd[6]; ...