[mythtv-users] duplicates in dtv_multiplex

[Ross Boylan]

My dtv_multiplex table has a few cases where the same frequency
appears in several mplexes:

select mplexid, sourceid, transportid, networkid, frequency/1e6 as
MHz, visible, hierarchy, serviceversion, updatetimestamp from
dtv_multiplex order by frequency, updatetimestamp;
MariaDB [mythconverg]>
+---------+----------+-------------+-----------+------+---------+-----------+----------------+---------------------+
| mplexid | sourceid | transportid | networkid | MHz  | visible |
hierarchy | serviceversion | updatetimestamp     |
+---------+----------+-------------+-----------+------+---------+-----------+----------------+---------------------+
|      16 |        1 |         259 |      NULL |   79 |       0 | a
     |             33 | 2022-09-21 13:28:35 |
|       3 |        1 |         381 |      NULL |  207 |       0 | a
     |             33 | 2022-09-19 21:03:42 |
|       2 |        1 |         377 |      NULL |  207 |       0 | a
     |             33 | 2023-09-10 13:53:37 |
|       4 |        1 |         397 |      NULL |  213 |       0 | a
     |             33 | 2022-09-19 21:03:42 |
|       6 |        1 |         401 |      NULL |  213 |       0 | a
     |             33 | 2023-02-25 11:44:37 |
|       5 |        1 |        9739 |      NULL |  473 |       0 | a
     |             33 | 2022-09-19 21:03:42 |
|       7 |        1 |         385 |      NULL |  473 |       0 | a
     |             33 | 2023-02-25 11:44:37 |
|       8 |        1 |        4069 |      NULL |  515 |       0 | a
     |             33 | 2022-09-19 21:03:42 |
For example, mplexid's 3 and 2 refer to the same frequency.
Is this likely to cause any trouble?
If I take all the entries in the channel table that refer to mplexid 2
and change them to mplexid 3, and then delete the row
for mplexid 2 from the dtv_multiplex table, is that likely to cause
any trouble (assuming I don't do it when when of the affected channels
is recording)?

Any direct change to these tables will put dtv_multiplex out of sync
with the scan information in channelscan_dtv_multiplex.

This situation arose because a program I wrote to handle channel
packing and rearranging operates by rewriting the frequency of an
existing plex; mplexid 2 was presumably using a different frequency.

I realized my update procedure wasn't quite right, and noticed this
problem while reviewing the code.  My thought is the code should be
moving the channels between existing plexes, or creating a new plex if
one doesn't exist.
In particular some atsc_major channels are split across different
plexes; a recent change split channels 4.1-4.5 across 3 different
frequencies.

Thanks.
Ross