2020年10月23日(金) 9:53 Ian Lawrence Barwick <barw...@gmail.com>: > > Hi > > From time to time I find myself in a situation where it would be very useful > to > be able to programatically determine whether a particular library is included > in > "shared_preload_libraries", which accepts a comma-separated list of values. > > Unfortunately it's not as simple as splitting the list on the commas, as while > that will *usually* work, the following is also valid: > > shared_preload_libraries = 'foo,bar,"baz ,"' > > and reliably splitting it up into its constituent parts would mean > re-inventing > a wheel (and worse possibly introducing some regular expressions into the > process, cf. https://xkcd.com/1171/ ). > > Now, while it's highly unlikely someone will go to the trouble of creating a > library name with commas and spaces in it, "highly unlikely" is not the same > as > "will definitely never ever happen". So it would be very handy to be able to > use > the same function PostgreSQL uses internally ("SplitDirectoriesString()") to > produce the guaranteed same result. > > Attached patch provides a new function "pg_setting_value_split()" which does > exactly this, i.e. called with a string containing such a list, it calls > "SplitDirectoriesString()" and returns the result as a set of text, e.g.: > > postgres# SELECT setting FROM pg_setting_value_split('foo,bar,"baz ,"'); > > setting > --------- > foo > bar > baz , > (3 rows) > > though a more likely use would be: > > SELECT setting FROM > pg_setting_value_split(current_setting('shared_preload_libraries')); > > Other GUCs this applies to: > > - local_preload_libraries > - session_preload_libraries > - unix_socket_directories
Having just submitted this, I realised I'm focussing on the GUCs which call "SplitDirectoriesString()" (as my specific uses case is for "shared_preload_libraries") but the patch does not consider the other GUC_LIST_INPUT settings, which call "SplitIdentifierString()", so as is, it might produce unexpected results for those. I'll rethink and submit an updated version. Regards Ian Barwick
