Insert Binary Large Object (BLOB) in PostgreSQL using libpq from remote machine

There are 2 types of blobs in PostgreSQL — BYTEA and Large Objects. I'd recommend against using large objects as you can not join them to tables.

For BYTEA you'd use something like this in libpq:

PGresult* put_data_to_tablename(  PGconn* conn,  int32_t id,  int data_size,  const char* const data) {  PGresult* result;  const uint32_t id_big_endian = htonl((uint32_t)id);  const char* const paramValues[] = { &id_big_endian, data };  const int nParams = sizeof(paramValues) / sizeof(paramValues[0]);  const int paramLenghts[] = { sizeof(id_big_endian), data_size };  const int paramFormats[] = { 1, 1 }; /* binary */  const int resultFormat = 0; /* text */  result = PQexecParams(    conn,    "insert into tablename (id, data) values ($1::integer, $2::bytea)",    nParams,    NULL, /* Types of parameters, unused as casts will define types */    paramValues,    paramLenghts,    paramFormats,    resultFormat  );  return result;}

Using libpqxx is the C++ way to do it, while libpq is the C API.

Here is a full example of how to do it using pqxx: How to insert binary data into a PostgreSQL BYTEA column using the C++ libpqxx API?

In short, the relevant C++ lines using libpqxx look like this:

void * bin_data = ...; // obviously do what you need to get the binary data...size_t bin_size = ...; // ...and the size of the binary datapqxx::binarystring bin( bin_data, bin_size );pqxx::result r = work.prepared( "test" )( bin ).exec();work.commit();