BUG #4079: libpq.dll very slow (unusable)

The following bug has been logged online:

Bug reference: 4079
Logged by: Pavel Golub
Email address: pavel(at)microolap(dot)com
PostgreSQL version: 8.3.1
Operating system: Windows XP SP2
Description: libpq.dll very slow (unusable)
Details:

Comparing 8.3.1 to 8.2.5 release INSERT of >1000 rows is very slow.

CREATE TABLE numbers
(
numberint integer NOT NULL,
numberstr character varying(80),
CONSTRAINT numbers_pkey PRIMARY KEY (numberint)
);

Inserts:
INSERT INTO numbers (numberint, numberstr) VALUES (1, 'One');
INSERT INTO numbers (numberint, numberstr) VALUES (2, 'Two');
INSERT INTO numbers (numberint, numberstr) VALUES (3, 'Three');
...
INSERT INTO numbers (numberint, numberstr) VALUES (1000, 'One thousand');

Program written on Delphi. Using libpq.dll 8.3.1.8075, and libpq 8.2.5.7260.
Both of them give the same results.

procedure Main(Db: TPSQLDatabase; SQL: string);
var
conninfo: string;
Conn: PGConn;
Res: PGResult;
cStart, cStop: cardinal;
begin
with Db do
Conninfo := Format('host = ''%s'' dbname = ''%s'' user = ''%s'' password
= ''%s'' port=''%d''',
[Host, DatabaseName, UserName, UserPassword, Port]);

Conn := PQConnectdb(PChar(ConnInfo));

If PQStatus(Conn) <> CONNECTION_OK then
begin
ShowMessage('CAN''T START connection!');
PQFinish(Conn);
Exit;
end;

cStart:=GetTickCount();

Res := PQExec(conn,PChar(SQL));
if PQResultStatus(res) <> PGRES_COMMAND_OK then
ShowMessage('CAN''T EXECUTE INSERTS');

cStop:=GetTickCount();
InfoMemo.Lines.Add('Execution time: '+IntToStr(cStop-cStart)+'ms');

PQClear(res);
PQFinish(Conn);
end;

Results with 10000 INSERTS:
- 984ms on PostgreSQL 8.2.7
- 25953ms on PostgreSQL 8.3.1

Result with 50000 INSERTS:
- 5063ms on PosgreSQL 8.2.7
- 26 minutes on PosgreSQL 8.3.1 (with 100% CPU usage)

The same behavior for pgAdmin III.

But psql works well when executing the request on both 8.2 and 8.3.

Tests were made under Windows XP only.