executeBatch(...) hangs indefinitely with no exception

[MartinHaeusler]

Please read https://stackoverflow.com/help/minimal-reproducible-example

Describe the issue
My application inserts rows via PreparedStatement.executeBatch(...). In some cases, this call never returns and blocks indefinitely.

Driver Version?
42.7.3

Java Version?
17.0.10

OS Version?
Alpine 3.19

PostgreSQL Version?
15.6

To Reproduce

// MyTable has a combined primary key consisting of (column2, column4, column5, column6)
// column1 is a timestamp, the rest are varchar(255)
private static final String SQL_INSERT = """
  INSERT 
      INTO MyTable(column1, column2, column3, column4, column5, column6) 
      VALUES (?, ?, ?, ?, ?, ?)
  ON CONFLICT(column2, column4, column5, column6) DO UPDATE
      SET column1 = EXCLUDED.column1,
          column2 = EXCLUDED.column2,
          column3 = EXCLUDED.column3,
          column4 = EXCLUDED.column4,
          column5 = EXCLUDED.column5,
          column6 = EXCLUDED.column6
  ;
""";

public void performInserts(Connection c, Iterable<SomeDataClass> elementsToInsert){
  try(var pStmt = c.prepareStatement(SQL_INSERT)){
      for(element in elementsToInsert){
          pStmt.setLong(1, elementToInsert.getLongValue());
          pStmt.setString(2, elementToInsert.getStringValue1());
          pStmt.setString(3, elementToInsert.getStringValue2());
          pStmt.setString(4, elementToInsert.getStringValue3());
          pStmt.setString(5, elementToInsert.getStringValue4());
          pStmt.setString(6, elementToInsert.getStringValue5());
          pStmt.addBatch();
      }
      pStmt.executeBatch();
  }
}

Expected behaviour
I would expect the insert to be executed and the method to return successfully.

Logs

This is the thread stack we're seeing:

"pool-5-thread-1" 
   java.lang.Thread.State: RUNNABLE
        at java.base@17.0.10/sun.nio.ch.Net.poll(Native Method)
        at java.base@17.0.10/sun.nio.ch.NioSocketImpl.park(NioSocketImpl.java:186)
        at java.base@17.0.10/sun.nio.ch.NioSocketImpl.park(NioSocketImpl.java:195)
        at java.base@17.0.10/sun.nio.ch.NioSocketImpl.implRead(NioSocketImpl.java:319)
        at java.base@17.0.10/sun.nio.ch.NioSocketImpl.read(NioSocketImpl.java:355)
        at java.base@17.0.10/sun.nio.ch.NioSocketImpl$1.read(NioSocketImpl.java:808)
        at java.base@17.0.10/java.net.Socket$SocketInputStream.read(Socket.java:966)
        at org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:161)
        at org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:128)
        at org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:113)
        at org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:73)
        at org.postgresql.core.PGStream.receiveChar(PGStream.java:465)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2154)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2133)
        at org.postgresql.core.v3.QueryExecutorImpl.flushIfDeadlockRisk(QueryExecutorImpl.java:1490)
        at org.postgresql.core.v3.QueryExecutorImpl.sendQuery(QueryExecutorImpl.java:1515)
        at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:559)
        at org.postgresql.jdbc.PgStatement.internalExecuteBatch(PgStatement.java:896)
        at org.postgresql.jdbc.PgStatement.executeBatch(PgStatement.java:919)
        at org.postgresql.jdbc.PgPreparedStatement.executeBatch(PgPreparedStatement.java:1677)
        at com.mycompany.MyService.performInserts(MyService.java)

This stack trace will remain the same for extended periods of time (minutes). I do not know exactly how many elements are in the batch, but I suspect no more than 1000 at most.

[davecramer]

see #194