Client reset imposes stricter character limits on table name

[jedelbo]

[Slack Thread|https://mongodb.slack.com/archives/G0121N9LJ14/p1701307619466459] captured from #privategroup by [~kiro.morkos@mongodb.com]

• [~kiro.morkos@mongodb.com]: Looking at a [HELP ticket|https://jira.mongodb.org/browse/HELP-52444?focusedCommentId=5914399&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-5914399] - this app is getting an error about a table name being too long during client reset, but not during normal bootstrap
  {"@t":"2023-11-29T16:27:43.2410074-06:00","@m":"Connection[2]: Session[5]: A fatal error occurred during client reset: 'class name too long (version: 0, last_integrated_remote_version: 0, origin_file_ident: 0, timestamp: 0). Please contact support.'","@l":"Error","SourceContext":"RealmSdk"}
  It appears that <https://github.com/realm/realm-core/blob/bc487096035a25e4d80e9b81e17d912d004047dd/src/realm/sync/instruction_applier.cpp#L88-L94|this method>, which is only used during client reset, enforces a max length of 57 characters (i assume the -6 comes from class_), and the app does indeed have a table with 58 characters. any idea why the normal bootstrap allows this table name?
• ~jonathan.reams@mongodb.com: because by the time you're able to bootstrap you've already created all your tables/columns?
• ~jonathan.reams@mongodb.com: i don't know why that function is only used in client resets though
• [~kiro.morkos@mongodb.com]: sorry, by "bootstrap" i meant the non-client reset case.
• [~kiro.morkos@mongodb.com]: like when they connect and do schema exchange outside of client reset, they don't hit this invariant
• ~jonathan.reams@mongodb.com: yeah, i think this may just be a case of the shrugs. going back 3 years that function is still unused
• ~jonathan.reams@mongodb.com: i don't know if there was a historical reason for only allowing 57 characters.
• [~kiro.morkos@mongodb.com]: but wouldn't the validation fail here in the non-client reset case?

  realm-core/src/realm/group.cpp

  Line 679 in bc48709

  Table* Group::do_add_table(StringData name, Table::Type table_type, bool do_repl)

  or does that name not include the class_ prefix?
• [~thomas.goyne@mongodb.com]: there's an off-by-one error there
• [~thomas.goyne@mongodb.com]: should be class_name.size() > Group::max_table_name_length - 6
• ~jonathan.reams@mongodb.com: ah, the best kind of error.
• [~kiro.morkos@mongodb.com]: ooooo wow 🤦 . that explains why a 58-character table name slips through the cracks 🙃
• [~kiro.morkos@mongodb.com]: wait, that would still fail though?
  class_name.size() = 58
58 > 63 - 6 and 58 >= 63-6

in the other codepath
name.size() = 64
64 > 63 <-- why is this okay? or does name not include class_ here either?

• [~thomas.goyne@mongodb.com]: what 64 character long name do they have? the longest table name I can find in the logs attached to that ticket is class_FieldResultDoc_tableResults_tableResults_checkListOptions , which is 63
• [~kiro.morkos@mongodb.com]: The table name is ...
• ~jonathan.reams@mongodb.com: did y'all figure this one out?

[jedelbo]

Duplicate of #7177