perf: read in_hot_standby GUC on connection

pgjdbc/src/main/java/org/postgresql/core/v3/ConnectionFactoryImpl.java

@@ -76,6 +76,8 @@ public class ConnectionFactoryImpl extends ConnectionFactory {
   private static final int AUTH_REQ_SASL_CONTINUE = 11;
   private static final int AUTH_REQ_SASL_FINAL = 12;
 
+  private static final String IN_HOT_STANDBY = "in_hot_standby";
+
   private ISSPIClient createSSPI(PGStream pgStream,
       @Nullable String spnServiceClass,
       boolean enableNegotiate) {
@@ -864,9 +866,15 @@ private void runInitialQueries(QueryExecutor queryExecutor, Properties info)
   }
 
   private boolean isPrimary(QueryExecutor queryExecutor) throws SQLException, IOException {
+    String inHotStandby = queryExecutor.getParameterStatus(IN_HOT_STANDBY);
+    if (inHotStandby != null && inHotStandby.equalsIgnoreCase("on")) {
+      return false;
+    }
+    // Host may not be in recovery but still have 'transaction_read_only=on' set,
+    // hence explicit check
     Tuple results = SetupQueryRunner.run(queryExecutor, "show transaction_read_only", true);
     Tuple nonNullResults = castNonNull(results);
-    String value = queryExecutor.getEncoding().decode(castNonNull(nonNullResults.get(0)));
-    return value.equalsIgnoreCase("off");
+    String queriedTransactionReadonly = queryExecutor.getEncoding().decode(castNonNull(nonNullResults.get(0)));
+    return queriedTransactionReadonly.equalsIgnoreCase("off");
   }
 }

pgjdbc/src/test/java/org/postgresql/test/hostchooser/MultiHostsConnectionTest.java

@@ -27,6 +27,7 @@
 import org.postgresql.test.TestUtil;
 import org.postgresql.util.HostSpec;
 import org.postgresql.util.PSQLException;
+import org.postgresql.util.PSQLState;
 
 import org.junit.Before;
 import org.junit.BeforeClass;
@@ -236,6 +237,29 @@ public void testConnectToMaster() throws SQLException {
     assertGlobalState(secondary1, "Secondary"); // was unknown, so tried to connect in order
   }
 
+  @Test
+  public void testConnectToPrimaryWithReadonlyTransactionMode() throws SQLException {
+    con = TestUtil.openPrivilegedDB();
+    con.createStatement().execute("ALTER DATABASE " + TestUtil.getDatabase() + " SET default_transaction_read_only=on;");
+    try {
+      getConnection(primary, true, fake1, primary1, secondary1);
+    } catch (PSQLException e) {
+      assertEquals(PSQLState.CONNECTION_UNABLE_TO_CONNECT.getState(), e.getSQLState());
+      assertGlobalState(fake1, "ConnectFail");
+      assertGlobalState(primary1, "Secondary");
+      assertGlobalState(secondary1, "Secondary");
+    } finally {
+      con = TestUtil.openPrivilegedDB();
+      con.createStatement().execute(
+          "BEGIN;"
+          + "SET TRANSACTION READ WRITE;"
+          + "ALTER DATABASE " + TestUtil.getDatabase() + " SET default_transaction_read_only=off;"
+          + "COMMIT;"
+      );
+      TestUtil.closeDB(con);
+    }
+  }
+
   @Test
   public void testConnectToSecondary() throws SQLException {
     getConnection(secondary, true, fake1, secondary1, primary1);
@@ -347,7 +371,7 @@ public void testLoadBalancing_secondary() throws SQLException {
         break;
       }
     }
-    assertEquals("Did not attempt to connect to all salve hosts", new HashSet<String>(asList(secondaryIP, secondaryIP2)),
+    assertEquals("Did not attempt to connect to all secondary hosts", new HashSet<String>(asList(secondaryIP, secondaryIP2)),
         connectedHosts);
     assertEquals("Did not attempt to connect to primary and fake node", 4, tryConnectedHosts.size());