postgresql JDBC驱动程序使用客户端时区

Question

I am using postgresql-42.2.2.jar jdbc driver and postgresql 9.6 server.

How can I configure the connection to use server timezone instead of client timezone?

Query:

select id, TO_TIMESTAMP(tbl.ended_time / 1000)
FROM tbl
where TO_TIMESTAMP(tbl.ended_time / 1000) >= now()::date + interval '1m'

Running a query with pgadmin I am getting the following result (which is correct)

"2185"  "2018-06-22 00:02:02-05"
"2186"  "2018-06-22 00:03:01-05"
"2187"  "2018-06-22 00:13:02-05"

but running the same query with JDBC driver the result is :

2169 2018-06-22 07:13:01.0
2181 2018-06-22 08:33:02.0
2180 2018-06-22 08:23:01.0
2185 2018-06-22 09:02:02.0
2186 2018-06-22 09:03:01.0
2187 2018-06-22 09:13:02.0

without where the running query with pgadmin the result is:

"2169"  "2018-06-21 22:13:01-05"
"2181"  "2018-06-21 23:33:02-05"
"2180"  "2018-06-21 23:23:01-05"
"2185"  "2018-06-22 00:02:02-05"
"2186"  "2018-06-22 00:03:01-05"
"2187"  "2018-06-22 00:13:02-05"

Here is the code:

static String URL = "jdbc:postgresql://some_ip:7000/db";
static String USERNAME = "test";
static String PASSWORD = "test";
static String JDBC_DRIVER = "org.postgresql.Driver";

public static void main(String[] args) {
    String query = "select id, TO_TIMESTAMP(tbl.ended_time / 1000) FROM tbl where TO_TIMESTAMP(tbl.ended_time / 1000) >= now()::date + interval '1m'";
    Connection conn = null;

    try {
        Class.forName(JDBC_DRIVER);
        conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        Statement st = conn.createStatement();          
        ResultSet rs = st.executeQuery(query);
        while (rs.next()) {             
            System.out.println(rs.getObject(1) + "--" + rs.getObject(2));
        }
        rs.close();
        st.close();
        conn.close();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } 

}

Answer 1

As explained here , the JDBC driver uses your local time zone and not the server time zone.

Unfortunately there is no easy way to change that behaviour or to query the server's time zone.

Also note that retrieving the data using an OffsetDateTime doesn't help much:

rs.getObject(2, OffsetDateTime.class)

because unfortunately, the driver returns all OffsetDateTime s with an offset of 0 , so the timezone information is lost.

So it seems that your best bet is probably to either hardcode the database's timezone and calculate your time limit in Java or to store the timezone separately in your DB and query it.

Answer 2

TL;DR: it has nothing to do with JDBC driver. The SQL is flawed.

What do you expect when comparing timestamp WITH time zone and timestamp withOUT time zone ? Your SQL is just plain wrong, and thus it produces weird results.

What do you expect out of now()::date ? Note: PostgreSQL documentation does NOT state which timezone now() would produce. It specifies just that "timezone will be there", however it could even change from one PG version to another one. So you are basically requesting "a random value".

Please clarify what do you want to achieve, then write an appropriate SQL. For instance, if you want to get records with timestamps "after 00:04:00 of the current day in a Europe/Berlin time zone", then you'd use something like

where TO_TIMESTAMP(tbl.ended_time / 1000) >= ((now() at time zone 'Europe/Berlin')::date + interval '4m')::timestamp at time zone 'Europe/Berlin'

The thing is there's no "start of a day" unless you specify which time zone you mean. pgjdbc populates session with default timezone ( TimeZone.getDefault() ), so it is used in implicit conversions, however I would strongly advice you from comparing with and without timezone kind of datatypes in SQL no matter what you use to execute.