4 Replies Latest reply on Feb 17, 2016 2:18 AM by plinn

    Access issue Lightroom catalog


      Dear Adobe-Team, Dear Community,


      I am a member of a team developing a program on OS X that needs access to the Lightroom catalog (lrcat). From the lrcat we read some information for further plugin exports. To retrieve these informations we handle the lrcat as SQL database and do some SQLite queries. The results we need will be delivered by these queries as output data and will be used for further processes by our export-plugin.


      If we are access the lrcat and request our SQLite queries under prior OS X versions and an running Lightroom CC instance everything works fine. But if we are working on the newest OS X El Capitan versions and Lightroom is running we are not able to access the lrcat anymore. The lrcat is locked until Lightroom will be closed.


      Does anyone still noticed a related problem? Does Lightroom changes anything on it's lrcat access under the newest OS X versions?


      Thanks in advance

        • 1. Re: Access issue Lightroom catalog
          johnrellis Most Valuable Participant

          Others have reported that since version 3, LR has locked the .lrcat catalog file, e.g. see: Lightroom SDK: Plugin API to unlock database temporarily. What others have done in the past is have their plugin exit LR, run a batch script that accesses the .lrcat file, then restart LR. That takes a little hackery with keyboard stuffing but can be made reasonably reliable.

          I vaguley recall in past years that LR locked the .lrcat file at the OS level, so that no other program could even read or copy the file while LR had it open.  But I can't find the relevant threads right now. However, a quick test with CC 2015.3 on Windows 10 and OS X 10.11 shows that it is possible to copy the .lrcat file while LR is running.  So one approach is to have your plugin copy the .lrcat file (and the .lrcat-journal file, which will contain recent changes to the database) to a temporary location and then open the copy for SQL access.


          Thinking about it, this hack may not always give you read-consistent access to the database. I think if you copy the .lrcat-journal file first and then .lrcat file, you're more likely to get a consistent point-in-time snapshot. But without some deeper thought and understanding of SQLite maintains its journal, it could be risky (give bad results).


          Absent an authoritative examination of how SQLite maintains its journal, exiting LR before accessing the .lrcat file is certainly the conservative way to go.

          • 2. Re: Access issue Lightroom catalog
            SilverHK Level 1

            Dear johnrellis,


            thanks for your fast reply. I also read something that the lrcat was already locked for Lightroom 3. However we tested it with Lightroom 5 and 6 under OS X 10.9 and 10.10 successfully. Unfortunately it doesn't work under OS X 10.11 anymore :-(



            We also thought about copying the lrcat, but this could be very inefficient if the catalog size is bigger than several 100MBs or GB.


            Your second solution (exiting Lightroom before accessing the lrcat) is also not very performant, because we need to access the lrcat at many times. This will be result in an infinite loop of closing and opening Lightroom again :-(

            Or maybe I don't understand whats done by the batch script exactly ... May it just stores another copy of the lrcat?!?

            • 3. Re: Access issue Lightroom catalog
              johnrellis Most Valuable Participant

              I agree with your assessment of both those approaches -- they both have significant drawbacks.  I haven't seen any better suggestions, though, other than to try to figure out how to avoid accessing the catalog via SQL.

              • 4. Re: Access issue Lightroom catalog

                There is a workaround to have read access to .lrcat database.

                In a terminal, with Lightroom not opened:

                — $ sqlite3 your/lightroom/catalog.lrcat

                — sqlite> pragma journal_mode=WAL;

                sqlite may say "wal"

                — keep this terminal opened and launch Lightroom with your catalog

                — after Lightroom launched, sqlite can be exited


                This bug seems to be provided by the version of libsqlite3 bundled in OSX. I've tried first to replace it (eg. /usr/lib/libsqlite3.dylib) with a newer version but the OS became unusable. I've also tried to set environments variables but Lightroom seems to be insensitive: it use invariably the OSX bundled version.