Re: Need example of usage DerelictPQ
On Wednesday, 24 December 2014 at 11:56:40 UTC, Suliman wrote:
Could anybody provide any simple examples of usage DerelictPQ.
I do not have experience of C, and I can't understand how to
use this driver.
I need just basics like connect, select and insert.
http://code.dlang.org/packages/derelict-pq
thanks!
A bit late, but maybe useful for others, and googling 'dlang
derelict postgres example' brings you here..
The default ubuntu (16.04) postgres version caused runtime errors
for me (DerelictPQ.load()), what worked was installation from
here:
https://www.postgresql.org/download/linux/ubuntu/
the example expects a postgres user/role 'sammy' with password
'sammypw' and a database 'sammy' with a table as shown in
comments and set up as here:
https://www.digitalocean.com/community/tutorials/how-to-install-and-use-postgresql-on-ubuntu-16-04
if you don't specify a host at PQconnectdb() then you might get
an error
'Peer authentication failed for user "sammy"'
when you run the binary as a OS user different from 'sammy', or
you would have to run the program as the postgres user like
sudo -iu sammy /path/to/prog
dub.json
{
"name": "prog",
"targetType": "executable",
"sourceFiles": [ "prog.d" ],
"dependencies": {
"derelict-pq": "~>2.2.0"
}
}
prog.d
import core.stdc.stdlib;
import std.stdio;
import std.conv;
import derelict.pq.pq;
/*
CREATE TABLE playground (
equip_id serial PRIMARY KEY,
type varchar (50) NOT NULL,
color varchar (25) NOT NULL,
location varchar(25) check (location in ('north', 'south',
'west', 'east', 'northeast', 'southeast', 'southwest',
'northwest')),
install_date date
);
INSERT INTO playground (type, color, location, install_date)
VALUES ('slide', 'blue', 'south', '2014-04-28');
INSERT INTO playground (type, color, location, install_date)
VALUES ('swing', 'yellow', 'northwest', '2010-08-16');
*/
int main(string[] args)
{
int retval = EXIT_SUCCESS;
DerelictPQ.load();
PGconn* conn = PQconnectdb("user = 'sammy' password = 'sammypw'
dbname = 'sammy' host = '127.0.0.1'");
if (PQstatus(conn) != CONNECTION_OK)
{
writefln("ERROR (connection): %s",
to!string(PQerrorMessage(conn)));
retval = EXIT_FAILURE;
}
else
{
writeln("OK (connection)");
PGresult* result = PQexec(conn, "select * from playground");
if (PQresultStatus(result) != PGRES_TUPLES_OK)
{
writefln("ERROR (result): %s",
to!string(PQerrorMessage(conn)));
retval = EXIT_FAILURE;
}
else
{
writeln("OK (result)");
int nbFields = PQnfields(result);
writeln("nbFields: ", nbFields);
int nbRows = PQntuples(result);
writeln("nbRows: ", nbRows);
for (int f; f < nbFields; f++)
{
writef("%16s", to!string(PQfname(result, f)));
}
writeln("");
for (int r; r < nbRows; r++)
{
for (int f; f < nbFields; f++)
{
ubyte* ub =
cast(ubyte*)(PQgetvalue(result, r, f));
int len = PQgetlength(result, r, f);
char[] c = cast(char[])ub[0..len];
string s = to!string(c);
writef("%16s", s);
}
writeln("");
}
}
PQclear(result);
}
PQfinish(conn);
return retval;
}
If someone has a better way to convert the PQgetvalue() to
string, i'm interested :)
The functions are as follows:
alias da_PQgetvalue = const(ubyte)*
function(const(PGresult)*,int,int);
alias da_PQgetlength = int function(const(PGresult)*,int,int);
have a nice day
Re: Need example of usage DerelictPQ
Adam, I trying to build simple app:
import std.stdio;
import postgres;
import database;
void main() {
auto db = new PostgreSql(dbname = test2);
foreach(line; db.query(SELECT * FROM customer)) {
writeln(line[0], line[customer_id]);
}
}
and getting next error:
D:\123dmd app.d database.d postgres.d
postgres.d(124): Error: struct database.Row member resultSet is
not accessible
postgres.d(139): Error: struct database.Row member row is not
accessible
Also I can't understand why I do not need specify login and pass
when I connection to DB?
Re: Need example of usage DerelictPQ
On Sunday, 28 December 2014 at 08:41:15 UTC, Suliman wrote: import postgres; import database; Those should include the package name: import arsd.postgres; Since it publicly imports the base clas, you don't need to import database yourself. (You do still need to pass all files to dmd though, your command line should remain the same. and getting next error: Those are protection errors because the package name isn't right, fix that and it should work (assuming you haven't modified the other source files) Also I can't understand why I do not need specify login and pass when I connection to DB? Postgresql authenticates based on what operating system user you're logged in as. You can change that in the server settings but normally the default works well.
Re: Need example of usage DerelictPQ
On 12/25/2014 3:03 PM, Suliman wrote: DerelictPQ is only a binding to libpq. The only difference is the DerelictPQ.load method. Just follow the libpq documentation. http://www.postgresql.org/docs/9.1/static/libpq.html Actually, Derelict binds to version 9.3, so the proper link should be http://www.postgresql.org/docs/9.3/static/libpq.html But could you look at my example and say what I am doing wrong? For my regret I do not know C and I have some problems with understanding this doc. I've never used libpq. Any C samples you find should be mostly directly translatable to D, with just a few minor adjustments. Look around for such a sample, or a libpq tutorial if such a thing exists, and try to port it over to D. Then if you have any trouble, I'm sure you can find help here with translating it.
Need example of usage DerelictPQ
Could anybody provide any simple examples of usage DerelictPQ. I do not have experience of C, and I can't understand how to use this driver. I need just basics like connect, select and insert. http://code.dlang.org/packages/derelict-pq thanks!
Re: Need example of usage DerelictPQ
I have done next:
string connString = psql -h localhost -p 5432 -U postgres -d
testdb;
package PGconn* conn;
@property bool nonBlocking(){ return PQisnonblocking(conn) == 1;
}
this(parseConfig parseconfig)
{
void connect()
{
try
{
DerelictPQ.load(getcwd ~
buildPath(\\libs\\libpq.dll));
conn = PQconnectdb(toStringz(connString));
if( !nonBlocking PQstatus(conn) !=
ConnStatusType.CONNECTION_OK )
throw new Exception(Can't connect to DB);
}
catch ( DerelictException de )
{
writefln(Failed to load libpq.dll: %s,
de.msg);
}
}
connect();
But it runtime I am getting next error:
object.Exception@source\app.d(203): Can't connect to DB
0x00402D31 in
D3app10PostgreSQL6__ctorMFC3app11parseConfigZ7connectMFZv at D:\Pr
oject\2014\seismoDownloader\source\app.d(203)
0x00402C3F in app.PostgreSQL
app.PostgreSQL.__ctor(app.parseConfig) at D:\Projec
t\2014\seismoDownloader\source\app.d(216)
0x0040208B in _Dmain at
D:\Project\2014\seismoDownloader\source\app.d(30)
What I am missing? Where I can to look right format of connection
string for this driver?
Re: Need example of usage DerelictPQ
I haven't used the derelict version but I have used the C library
itself and wrapped it briefly in my postgres.d here:
https://github.com/adamdruppe/arsd/blob/master/postgres.d
(implements an interface from database.d in the same repo)
I used very, very little of the library, but it is enough to get
basic results.
Your connection string can just be dbname=NAME_HERE. Given your
command line, dbname=testdb would be the first one I try.
Here's the docs on those strings:
http://www.postgresql.org/docs/current/static/libpq-connect.html#LIBPQ-PARAMKEYWORDS
Your host and port are the default, so no need to list them. You
might need to set the user, but a better option there might be to
grant your regular user (whatever one you are logged into the
operating system as) permission to access the database, then the
default will work for that too.
The second class in my file shows how to get basic results.
string[] row;
for(int i = 0; i numFields; i++) {
string a;
if(PQgetisnull(res, position, i))
a = null;
else {
a = to!string(PQgetvalue(res, position, i),
PQgetlength(res, position, i));
}
row ~= a;
}
gets it as an array of strings. This simple option loses the type
checking you can get from the database but it works for a lot of
stuff too.
Re: Need example of usage DerelictPQ
On Wednesday, 24 December 2014 at 14:08:53 UTC, Adam D. Ruppe wrote: I haven't used the derelict version but I have used the C library itself and wrapped it briefly in my postgres.d here: https://github.com/adamdruppe/arsd/blob/master/postgres.d Thanks! But few questions: 1. how to build it with dub? 2. I tried to: dmd app.d database.d postgres.d but get message that File Not Found pq.lib 3. Can I build it's simply: dmd app.d ? Would it able to import other 2 file?
Re: Need example of usage DerelictPQ
On Wednesday, 24 December 2014 at 19:26:11 UTC, Suliman wrote: 1. how to build it with dub? I don't know, I don't use dub. 2. I tried to: dmd app.d database.d postgres.d but get message that File Not Found pq.lib Download the lib file from me here: http://arsdnet.net/dcode/pq.lib You'll still need the DLLs, the difference between my lib and the Derelict one is I bind it statically whereas Derelict loads the dll at runtime. Both need the dll, but Derelict skips the lib step. It is the same API though, so you could also just use my source as an example to guide writing your derelict based program. 3. Can I build it's simply: dmd app.d ? Would it able to import other 2 file? Won't work since then the other functions won't be compiled, always need to pass them along to dmd too or build a separate .lib (but that's not really worth the hassle)
Re: Need example of usage DerelictPQ
On 12/24/2014 8:56 PM, Suliman wrote: Could anybody provide any simple examples of usage DerelictPQ. I do not have experience of C, and I can't understand how to use this driver. I need just basics like connect, select and insert. http://code.dlang.org/packages/derelict-pq thanks! DerelictPQ is only a binding to libpq. The only difference is the DerelictPQ.load method. Just follow the libpq documentation. http://www.postgresql.org/docs/9.1/static/libpq.html
Re: Need example of usage DerelictPQ
On 12/25/2014 11:23 AM, Mike Parker wrote: On 12/24/2014 8:56 PM, Suliman wrote: Could anybody provide any simple examples of usage DerelictPQ. I do not have experience of C, and I can't understand how to use this driver. I need just basics like connect, select and insert. http://code.dlang.org/packages/derelict-pq thanks! DerelictPQ is only a binding to libpq. The only difference is the DerelictPQ.load method. Just follow the libpq documentation. http://www.postgresql.org/docs/9.1/static/libpq.html Actually, Derelict binds to version 9.3, so the proper link should be http://www.postgresql.org/docs/9.3/static/libpq.html
Re: Need example of usage DerelictPQ
DerelictPQ is only a binding to libpq. The only difference is the DerelictPQ.load method. Just follow the libpq documentation. http://www.postgresql.org/docs/9.1/static/libpq.html Actually, Derelict binds to version 9.3, so the proper link should be http://www.postgresql.org/docs/9.3/static/libpq.html But could you look at my example and say what I am doing wrong? For my regret I do not know C and I have some problems with understanding this doc.
