Prevent folder order inconsistency #1877
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I noticed that running two concurrent instances of Vienna led to inconsistencies which led Vienna to reset its folders to alphabetical order. This change will make new versions of Vienna have a safer behavior. However, problems can still arise when an older version of Vienna (or any app manipulating messages.db) is launched while a corrected version is already running. Issues ViennaRSS#1768, ViennaRSS#1779 and ViennaRSS#1824
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Have you considered transactions? FMDatabaseQueue supports those as well. I don't know if those would affect database access across app instances though. |
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If you have a proper database server, transactions are made exactly for the purpose of preventing simultaneous access to the same data. The kind of access that cannot happen in parallel (e.g. writing or reading+writing or even only reading) is regulated by the transaction isolation level. However in this case I think, the DB is embedded twice, and not run as a server. I don't know enough about this particular database to say if it somehow also maintains transactional access when embedded, but that seems unlikely to me. |
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I noticed that running two concurrent instances of Vienna led to inconsistencies which led Vienna to reset its folders to alphabetical order.
This change will make new versions of Vienna have a safer behavior. However, problems can still arise when an older version of Vienna (or any app manipulating messages.db) is launched while a corrected version is already running.
Issues #1768, #1779 and #1824