Question

I’m using this:

COPY( select field1, field2, field3 from table ) TO ‘C://Program
Files/PostgreSql//8.4//data//output.dat’ WITH BINARY

To export some fields to a file, one of them is a ByteA field. Now, I need to read the file with a custom made program.

How can I parse this file?

Answer 1

The general format of a file generated by COPY...BINARY is explained in the documentation, and it’s non-trivial.

bytea contents are the most easy to deal with, since they’re not encoded.

Each other datatype has its own encoding rules, which are not described in the documentation but in the source code. From the doc:

To determine the appropriate binary format for the actual tuple data
you should consult the PostgreSQL source, in particular the *send and
*recv functions for each column’s data type (typically these functions are found in the src/backend/utils/adt/ directory of the source
distribution).