我正在尝试按照文档中的建议使用 PostgreSQL CopyManager copyIn功能，COPY FROM STDIN以非常快速地将 InputStream 复制到数据库表中。我正在考虑使用它来连续流式传输要写入表的行，以及当我接收/处理一个表时。然而，下面的快速而肮脏的示例代码似乎被卡住copyIn并且没有写入表格。
任何人都知道我在这里缺少什么或者我的理解是错误的吗？
import java.sql.*;
import java.util.concurrent.Callable;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import org.postgresql.core.BaseConnection;
import org.postgresql.copy.CopyManager;
public class PGConnectTest {
public static void main(String[] args) {
try {
try (Connection connection = DriverManager.getConnection("jdbc:postgresql://XX.XX.XX.XX:9432/somedb", "someadmin", "somepassword");
BaseConnection pgcon = (BaseConnection)connection;
PipedInputStream is = new PipedInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
PipedOutputStream os = new PipedOutputStream(is);
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));) {
ExecutorService executorService = Executors.newSingleThreadExecutor();
Callable callable = () -> {
Thread.sleep(3000);
String frmtStr = "%s\t{\"id\":%s, \"somefield\":\"%s\"}\n";
String row = null;
for(int i=1; i<10; i++) {
row = String.format(frmtStr, i, i, ("row"+i));
System.out.print(row);
bw.write(row);
}
bw.write("\n");
bw.flush();
System.out.println("WRITTEN!");
return true;
};
executorService.submit(callable);
System.out.println(connection);
CopyManager copyManager = new CopyManager(pgcon);
String copySql = "COPY dcm.testtbl FROM STDIN";
executorService.submit(() -> copyManager.copyIn(copySql, br));
Thread.sleep(10000);
System.out.println("QUITTING");
} catch (Exception e) {
throw e;
}
} catch(Exception ex) {
System.out.println(ex);
}
}
}
该表的架构testtbl如下，
create table testtbl (
id integer primary key,
jsnclm jsonb
)
控制台输出是（它不会返回，需要使用 CTRL+C 来杀死它），
C:\Users\ml410408\Documents\Useful Lookups\POSTGRESQL>java -cp ".;postgresql-42.2.18.jar" PGConnectTest
org.postgresql.jdbc.PgConnection@41975e01
1 {"id":1, "somefield":"row1"}
2 {"id":2, "somefield":"row2"}
3 {"id":3, "somefield":"row3"}
4 {"id":4, "somefield":"row4"}
5 {"id":5, "somefield":"row5"}
6 {"id":6, "somefield":"row6"}
7 {"id":7, "somefield":"row7"}
8 {"id":8, "somefield":"row8"}
9 {"id":9, "somefield":"row9"}
WRITTEN!
QUITTING
更新：
一旦我将COPYsql 命令的格式从默认的 TEXT 更改为 CSV 并传入 csv 记录，它就不再卡住但什么也不做（意味着表中没有记录），即使它返回的结果与以前不同。
import java.sql.*;
import java.util.concurrent.Callable;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import org.postgresql.core.BaseConnection;
import org.postgresql.copy.CopyManager;
public class PGConnectTest {
public static void main(String[] args) {
try {
try (Connection connection = DriverManager.getConnection("jdbc:postgresql://XX.XX.XX.XX:9432/somedb", "someadmin", "somepassword");
BaseConnection pgcon = (BaseConnection)connection;
PipedInputStream is = new PipedInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
PipedOutputStream os = new PipedOutputStream(is);
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));) {
ExecutorService executorService = Executors.newSingleThreadExecutor();
Callable callable = () -> {
Thread.sleep(3000);
String frmtStr = "%s,'{\"id\":%s,\"somefield\":\"%s\"}'\n";
String row = null;
for(int i=1; i<10; i++) {
row = String.format(frmtStr, i, i, ("row"+i));
System.out.print(row);
bw.write(row);
}
bw.write("\n");
bw.write("'\\.'\n");
System.out.println("'\\.'\n");
bw.flush();
os.flush();
System.out.println("WRITTEN!");
return true;
};
executorService.submit(callable);
System.out.println(connection);
CopyManager copyManager = new CopyManager(pgcon);
String copySql = "COPY dcm.testtbl FROM STDIN FORMAT CSV DELIMITER ','";
executorService.submit(() -> copyManager.copyIn(copySql, br));
Thread.sleep(5000);
System.out.println(br.ready());
while (br.ready()) {
System.out.println("LINE : " + br.readLine());
}
executorService.shutdown();
System.out.println("QUITTING");
} catch (Exception e) {
throw e;
}
System.out.println("QUITTING FINALLY");
} catch(Exception ex) {
System.out.println(ex);
}
}
}
谢谢