On Thu, 2010-10-28 at 13:55 -0400, Greg Stein wrote: > On Thu, Oct 28, 2010 at 12:36, Hyrum K. Wright > <[email protected]> wrote: > > On Thu, Oct 28, 2010 at 11:29 AM, Mark Phippard <[email protected]> wrote: > >> On Thu, Oct 28, 2010 at 12:23 PM, Hyrum K. Wright > >> <[email protected]> wrote: > >>> On Thu, Oct 28, 2010 at 10:09 AM, Julian Foad <[email protected]> > >>> wrote: > >>>> Bert and Erik and Philip and I discussed on IRC today the merits, or > >>>> lack of merits, of allowing repos-id/repos-relpath to be elided in the > >>>> NODES table BASE layer (op_depth = 0). > >>>> > >>>> * The data is not currently elided. > >>>> > >>>> * Some queries for locks currently assume the data is not elided. > >>>> > >>>> * Elision could save a bit of DB size, which *might* contribute to a > >>>> little bit of general DB performance. > >>>> > >>>> * The option of elision results in the need for all users of this data > >>>> to call svn_wc__db_scan_base_repos() or the internal version > >>>> scan_upwards_for_repos(), which is an extra maintenance burden and extra > >>>> run-time cost. > >>>> > >>>> We concluded it would be better to require the columns to be always > >>>> filled in. I'll do this soon if no objections. > >>> > >>> As I understand it, our original intention for elision was to make > >>> switch and relocate go much faster, since only one row would be > >>> updated instead of the entire tree. If that creates too much of a > >>> burden elsewhere, then yes, we can probably nuke it (and we can > >>> probably write a good enough query to make the relatively uncommon > >>> operations of switch and relocate only negligibly slower). > >>> > >>> This is one use case, however, and isn't necessarily the only one. > >> > >> At the same time, with code written to properly leverage SQL this is > >> the sort of scenario that we should not worry about anymore. SQLite > >> ought to be able to update all the rows in the DB faster than our old > >> code could walk the tree and open all the entries files, let alone > >> rewrite them. > > > > Correct. And we still have to do the update crawl on a switch or relocate, > > no? > > Dunno that we would have to do a crawl (unless you are limiting the > depth), but I think you guys are correct: on balance, the concept of > elision is costing us more than it is saving us. > > +1 to eliminating the concept, and ensuring that we always write them > out (it may look like it now, but be careful... there could be edge > cases)
Great. The only tests that fail when I make scan_upwards_for_repos() abort at the point where it's about to scan upwards are: db-test 1 entries-compat-test 1 2 and those are because the DB rows are hand-coded. Easily fixed. > I would suggest making the columns NOT NULL in the schema. I don't > think we need to attempt a format bump to adjust older working copies > -- they just won't have the sqlite benefits from the additional schema > details. The repos columns are shared between BASE and WORKING op_depth layers, and we still allow them to be null when op_depth > 0, so we can't say "NOT NULL". - Julian
