On 24 November 2014 at 21:04, Robert Haas <robertmh...@gmail.com> wrote:
> On Mon, Nov 24, 2014 at 3:26 PM, Thom Brown <t...@linux.com> wrote: > > I haven't seen this mentioned anywhere (although it may have as I haven't > > read through the entire history of it), but would others find it useful > to > > have ALTER SYSTEM support comments? > > Oh, please no. > > The main thing that caused us to have no way of modifying > postgresql.conf via SQL for so many years is that it's not clear how > you can sensibly rewrite a file with comments in it. For example, the > default postgresql.conf file has stuff like this in it: > > #variable = someval > > If variable gets set to a non-default value, you might want to > uncomment that line, but now you have to parse the comments, which > will be tedious and error-prone and sometimes make stupid decisions: > > #Back in days of yore when dinosaurs ruled the earth, we had > #autovacuum_naptime=1h, but that turned out to be a bad idea. > # > #autovacuum_naptime=1min I'm not sure this is an argument against supporting comments to postgresql.auto.conf since it's specifically intended not to be edited by humans, and commenting out a parameter will remove it from the file upon further ALTER SYSTEM invocations anyway. It would perhaps be OK to have comments in postgresql.conf.auto if > they were designated in some way that told us which specific comment > was associated with which specific setting. But we need to be very > careful not to design something that requires us to write a parser > that can ferret out human intent from context clues. Perhaps the parser could automatically remove any comment blocks which are followed by a blank/empty line. So if we had: --------------------- work_mem = '4MB' # Set this lower as we're using a really fast disk interace #seq_page_cost = '0.5' # Set random_page_cost lower as we're using an SSD random_page_cost = '1.0' # This line has been manually added by a human without a newline maintenance_work_mem = '1GB' # This is an orphaned comment --------------------- I would expect the next modification to the file to cause reduce it to: --------------------- work_mem = '4MB' # Set random_page_cost lower as we're using an SSD random_page_cost = 1.0 # This line has been manually added maintenance_work_mem = '1GB' --------------------- Thom
