Hello,
after hours of documentations/boards/mailinglists and no progress I may ask you: How do I 'encode' my data to use it for binary transport using libpq's PQexecParams(.)
?
Simple variables are just in big endian order:
PGconn *conn;
PGresult *res;
char *paramValues[1];
int paramLengths[1];
int paramFormats[1];
conn = PQconnectdb(CONNINFO);
// -- (1) -- send a float value
float val_f = 0.12345678901234567890; // float precision: ~7 decimal digits
// alloc some memory & write float (in big endian) into
paramValues[0] = (char *) malloc(sizeof(val_f));
*((uint32_t*) paramValues[0]) = htobe32(*((uint32_t*) &val_f)); // host to big endian
paramLengths[0] = sizeof(val_f);
paramFormats[0] = 1; // binary
res = PQexecParams(conn, "SELECT $1::real ;", //
1, // number parameters
NULL, // let the backend deduce param type
paramValues, //
paramLengths, //
paramFormats, //
0); // return text
printf("sent float: %s \n", PQgetvalue(res, 0, 0));
// --> sent float: 0.123457
and like this also double, int, etc ...
But how about ARRAYs?
float vals_f[] = {1.23, 9.87};
// alloc some memory
paramValues[0] = (char *) malloc(sizeof(float) * 2);
// ???? paramValues[0] = ??????
paramLengths[0] = sizeof(float) * 2;
paramFormats[0] = 1; // binary
res = PQexecParams(conn, "SELECT $1::real[] ;", //
1, // number parameters
NULL, // let the backend deduce param type
paramValues, //
paramLengths, //
paramFormats, //
0); // return text
printf("sent float array: %s \n", PQgetvalue(res, 0, 0));
Is there any working example of transfering ARRAY data in PostgreSQL's binary format?
The code in backend/utils/adt/
doesn't help me much (except I now know there is a ARRAYTYPE, but not how to use them) :-(
I just need a function char* to_PQbin(float [] input, int length)
for passing to paramValues[.]
...
Thanks a lot, Tebas
PS: What is the suggested way of converting simple variables (rather than my htobe32(.)
)?