working on dropping old mails

src/main/java/de/srsoftware/widerhall/data/Database.java

@@ -11,6 +11,7 @@ import java.sql.SQLException;
 import java.util.*;
 
 import static de.srsoftware.widerhall.Util.t;
+import static de.srsoftware.widerhall.data.MailingList.HOLD_TIME;
 
 /**
  * @author Stephan Richter, 2022
@@ -280,9 +281,30 @@ public class Database {
         if (!tableExists(MailingList.TABLE_NAME)) MailingList.createTable();
         if (!tableExists(ListMember.TABLE_NAME)) ListMember.createTable();
         if (!tableExists(Post.TABLE_NAME)) Post.createTable();
+        if (!columnExists(MailingList.TABLE_NAME,HOLD_TIME)) MailingList.createHoldTimeColumn();
         return this;
     }
 
+    private boolean columnExists(String tableName, String columnName) throws SQLException {
+        var rs = Database.open().select("pragma_table_info('"+tableName+"')","COUNT(*) AS num").where("name",columnName).compile().exec();
+        try {
+            if (rs.next()) return rs.getInt("num") > 0;
+        } finally {
+            rs.close();
+        }
+        return false;
+    }
+
+    public void createColumn(String tableName, String colName, String...typeArgs) throws SQLException {
+        var sql = new StringBuilder("ALTER TABLE ")
+                .append(tableName)
+                .append(" ADD COLUMN ")
+                .append(colName)
+                .append(" ")
+                .append(String.join(" ",typeArgs));
+        new Request(sql).compile().run();
+    }
+
     /**
      * prepare a deletion statement
      * @param tableName