CR

distribution/lib/Standard/Database/0.0.0-dev/src/Connection/Connection.enso

@@ -404,16 +404,22 @@ type Connection
          registry - but that means it was created by Enso as a hidden table.
     generate_dry_run_table_name : Text -> Text
     generate_dry_run_table_name self table_name =
+        max_length = (self.max_table_name_length.if_nothing 60) - 1
         go ix =
             prefix = "enso-dry-run-" + if ix == 0 then "" else ix.to_text + "-"
-            max_length = (self.max_table_name_length.if_nothing 60) - 1
-            name = prefix + table_name.take (max_length - prefix.length)
-            ## The dry run name is ok if it is already registered (that means it
-               may exist in the Database, but it was created by other dry runs
-               and is safe to overwrite) or if it does not exist in the database.
-            name_ok = (self.hidden_table_registry.is_registered name) || (self.table_exists name . not)
-            if name_ok then name else
-                @Tail_Call go (ix + 1)
+            ## This check ensures that if all possible names are taken, the
+               method will not loop forever but report an error. It should never
+               occur in practice - it would mean that the Database contains
+               unimaginable amounts of dry run tables or has impractically small
+               table name length limit.
+            if prefix.length > max_length then Error.throw (Illegal_State.Error "Reached the table name length limit ("+max_length.to_text+") while trying to find a unused table name. It seems that all possible names are already taken. The Database may need to be cleaned up for dry run to work." else
+                name = (prefix + table_name) . take max_length
+                ## The dry run name is ok if it is already registered (that means it
+                   may exist in the Database, but it was created by other dry runs
+                   and is safe to overwrite) or if it does not exist in the database.
+                name_ok = (self.hidden_table_registry.is_registered name) || (self.table_exists name . not)
+                if name_ok then name else
+                    @Tail_Call go (ix + 1)
         go 0
 
     ## PRIVATE