func (c *driverConn) Prepare(query string) (driver.Stmt, error) {
// Generate unique statement name.
stmtname := strconv.Itoa(c.stmtNum)
cstmtname := C.CString(stmtname)
c.stmtNum++
defer C.free(unsafe.Pointer(cstmtname))
stmtstr := C.CString(query)
defer C.free(unsafe.Pointer(stmtstr))
res := C.PQprepare(c.db, cstmtname, stmtstr, 0, nil)
err := resultError(res)
if err != nil {
C.PQclear(res)
return nil, err
}
stmtinfo := C.PQdescribePrepared(c.db, cstmtname)
err = resultError(stmtinfo)
if err != nil {
C.PQclear(stmtinfo)
return nil, err
}
defer C.PQclear(stmtinfo)
nparams := int(C.PQnparams(stmtinfo))
statement := &driverStmt{stmtname, c.db, res, nparams}
runtime.SetFinalizer(statement, (*driverStmt).Close)
return statement, nil
}
func (c *libpqConn) Prepare(query string) (driver.Stmt, error) {
// check our connection's query cache to see if we've already prepared this
cached, ok := c.stmtCache[query]
if ok {
return cached, nil
}
// create unique statement name
// NOTE: do NOT free cname here because it is cached in c.stmtCache;
// all cached statement names are freed in c.Close()
cname := C.CString(strconv.Itoa(c.stmtNum))
c.stmtNum++
cquery := C.CString(query)
defer C.free(unsafe.Pointer(cquery))
// initial query preparation
cres := C.PQprepare(c.db, cname, cquery, 0, nil)
defer C.PQclear(cres)
if err := resultError(cres); err != nil {
return nil, err
}
// get number of parameters in this query
cinfo := C.PQdescribePrepared(c.db, cname)
defer C.PQclear(cinfo)
if err := resultError(cinfo); err != nil {
return nil, err
}
nparams := int(C.PQnparams(cinfo))
// save statement in cache
stmt := &libpqStmt{c: c, name: cname, query: query, nparams: nparams}
c.stmtCache[query] = stmt
return stmt, nil
}