I just found this old posting on google. Now my question is how can I read an
integer value from the PGresult using the binary format? Can someone plz
gimme a code example? (please mail to me, because I have not subscribed to
the list)
Easy peasy:
/* (in C++, actually would give simpler code in C) */
// To submit the query
bool PgConn::SendPrepared(const string& name, const vector<const char*>& values, const vector<int>& lengths, const vector<int>& isBinary) {
if (values.size() != lengths.size() || values.size() != isBinary.size())
return Error("PgConn::SendPrepared: All parameter arrays must have same size");
// for (int i = 0; i != values.size(); i++)
// printf ("Query parameter %d, length %d, binary %d: '%s'\n", i, lengths[i], (int)isBinary[i], values[i]);
if (! PQsendQueryPrepared(m_Conn, name.c_str(), values.size(), &values.front(), &lengths.front(), &isBinary.front(), 1 /* want binary result */))
return Error();
return Success(); }
/* ... then after reading the PGresult */
static int NetworkIntFromBuffer(const char* buff) {
// Make a network-byte-ordered integer from the fetched data
const int *network = reinterpret_cast<const int*>(buff);
// Convert to host (local) byte order and return
int host = ntohl(*network);
return host;
}
int PgColumn::GetInt(int row) {
if (IsNull(row) || row > Rows() || GetLength(row) != 4)
return 0;return NetworkIntFromBuffer(PQgetvalue(m_Res, row, m_Col)); }
Thanks a bunch! Now here's the old posting:
On Monday 27 October 2003 09:15, Tomasz Myrta wrote:Dnia 2003-10-27 00:08, UÅytkownik creid napisaÅ:Problem: Assigning a COUNT(*) result into an integer variable in my C
program consistently fails except when I assign the same result to a char
variable. I can only assume that the internal data type the COUNT
function uses is integer.
Can anyone help put me in the proper mindset so I may deal with this, seemingly simple issue, to resolution.
I need the integer result to to help me satisfy a dynamic memory
requirement... COUNT(*) result will tell me how many rows of data I need
to malloc and I cannot perform a math operation on a char variable.
All libpq results are strings. some_int_value=atoi(PQgetvalue(...))
Not true anymore with protocol v3, which added the binary format. Text format
is still the default.
Anyway why do you need count(*) ? When you retrieve your rows, you can
always check how many are them using PQntuples(...) and then malloc your
memory tables.
Regards, Tomasz Myrta
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