Re: [COMMITTERS] pgsql: Make it easy to detach completely from shared memory.
Re: [COMMITTERS] pgsql: Make it easy to detach completely from shared memory.
От:
Tom Lane <tgl@sss.pgh.pa.us>
Дата:
Robert Haas writes: > On Tue, Mar 18, 2014 at 8:41 AM, Simon Riggs wrote: >> Perhaps we should consider a parameter for PGSharedMemoryDetach() ? > Yeah, maybe. It seems like a possible modularity violation, because > the PGSharedMemory... stuff has heretofore not needed to know anything > about DSM, and apart from this one function, it still wouldn't. That was exactly the reason we rejected that design upthread. PGSharedMemoryDetach is specific to the main shmem segment, and in fact has multiple OS-dependent implementations. You could make an argument for inventing some new wrapper function that calls both PGSharedMemoryDetach and dsm_detach_all, but I don't believe that the existing flavors of that function should know about DSM. regards, tom lane
Re: [COMMITTERS] pgsql: Make it easy to detach completely from shared memory.
От:
Robert Haas <robertmhaas@gmail.com>
Дата:
On Tue, Mar 18, 2014 at 8:41 AM, Simon Riggs wrote: > On 18 March 2014 11:59, Robert Haas wrote: >> Make it easy to detach completely from shared memory. >> >> The new function dsm_detach_all() can be used either by postmaster >> children that don't wish to take any risk of accidentally corrupting >> shared memory; or by forked children of regular backends with >> the same need. This patch also updates the postmaster children that >> already do PGSharedMemoryDetach() to do dsm_detach_all() as well. >> >> Per discussion with Tom Lane. > > I think we need to document exactly why dsm_detach_all() isn't simply > part of PGSharedMemoryDetach() ? > > Having two calls seems like a recipe for error in core and extensions. > > Perhaps we should consider a parameter for PGSharedMemoryDetach() ? Yeah, maybe. It seems like a possible modularity violation, because the PGSharedMemory... stuff has heretofore not needed to know anything about DSM, and apart from this one function, it still wouldn't. On the other hand, your argument is good, too. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
Re: [COMMITTERS] pgsql: Make it easy to detach completely from shared memory.
От:
Simon Riggs <simon@2ndQuadrant.com>
Дата:
On 18 March 2014 11:59, Robert Haas wrote: > Make it easy to detach completely from shared memory. > > The new function dsm_detach_all() can be used either by postmaster > children that don't wish to take any risk of accidentally corrupting > shared memory; or by forked children of regular backends with > the same need. This patch also updates the postmaster children that > already do PGSharedMemoryDetach() to do dsm_detach_all() as well. > > Per discussion with Tom Lane. I think we need to document exactly why dsm_detach_all() isn't simply part of PGSharedMemoryDetach() ? Having two calls seems like a recipe for error in core and extensions. Perhaps we should consider a parameter for PGSharedMemoryDetach() ? -- Simon Riggs http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
Re: [COMMITTERS] pgsql: Make it easy to detach completely from shared memory.
От:
Simon Riggs <simon@2ndQuadrant.com>
Дата:
On 18 March 2014 13:51, Tom Lane wrote: > Robert Haas writes: >> On Tue, Mar 18, 2014 at 8:41 AM, Simon Riggs wrote: >>> Perhaps we should consider a parameter for PGSharedMemoryDetach() ? > >> Yeah, maybe. It seems like a possible modularity violation, because >> the PGSharedMemory... stuff has heretofore not needed to know anything >> about DSM, and apart from this one function, it still wouldn't. > > That was exactly the reason we rejected that design upthread. > PGSharedMemoryDetach is specific to the main shmem segment, and in fact > has multiple OS-dependent implementations. > > You could make an argument for inventing some new wrapper function that > calls both PGSharedMemoryDetach and dsm_detach_all, but I don't believe > that the existing flavors of that function should know about DSM. I'm not bothered which we choose, as long as its well documented to ensure people that use those calls don't detach from just one when they really would wish to detach from both. -- Simon Riggs http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
