Re: libpq and mysterious "invalid byte sequence for encoding UTF8".

=?UTF-8?B?SmnFmcOtIFBhdmxvdnNrw70=?= <jiri(at)pavlovsky(dot)eu> writes:
>     Jan 26 08:40:57 ip-172-16-10-94 postgres[11334]: [113-1] 2021-01-26
> 09:40:57.505 CET [11334] jira(at)project-syndicate LOG:  execute <unnamed>:
>    
>         UPDATE contacts SET Pos = $1::varchar, Title = $2::varchar,
> PaperID = $3::int, FirstName = $4::varchar, LastName = $5::varchar, Func
> = $6::varchar, Tel1 = $7::text, Fax1 = $8::text, Email1 = $9::varchar,
> Tel2 = $10::text, Fax2 = $11::text, Email2 = $12::varchar, MainContact =
> $13::boolean, PublDataContact = $14::boolean, InvContact = $15::boolean
> WHERE ContactID = $16::int
>         Jan 26 08:40:57 ip-172-16-10-94 postgres[11334]: [113-2]
> 2021-01-26 09:40:57.505 CET [11334] jira(at)project-syndicate DETAIL: 
> parameters: $1 = NULL, $2 = NULL, $3 = '1702', $4 = NULL, $5 = NULL, $6
> = NULL, $7 = NULL, $8 = NULL, $9 = NULL, $10 = NULL, $11 = NULL, $12 =
> NULL, $13 = NULL, $14 =  NULL, $15 = NULL, $16 = '14340'
>         Jan 26 08:40:57 ip-172-16-10-94 postgres[11334]: [114-1]
> 2021-01-26 09:40:57.544 CET [11334] jira(at)project-syndicate ERROR: 
> invalid byte sequence for encoding "UTF8": 0x80

This log entry shows that your query text and parameters all made it to
the backend just fine. So I don't think your issue is on the client side.
I'm wondering if the error could be from (say) triggers doing fancy data
manipulations. Noting your use of ON UPDATE CASCADE, it'd be worth
checking indirectly-affected tables as well.

regards, tom lane