[[!tag patch]] The available [[ikiwiki/pagespec/sorting]] methods are currently hard-coded in IkiWiki.pm, making it difficult to add any extra sorting mechanisms. I've prepared a branch which adds 'sort' as a hook type and uses it to implement a new `meta_title` sort type. Someone could use this hook to make `\[[!inline sort=title]]` prefer the meta title over the page name, but for compatibility, I'm not going to (I do wonder whether it would be worth making sort=name an alias for the current sort=title, and changing the meaning of sort=title in 4.0, though). > What compatability concerns, exactly, are there that prevent making that > change now? --[[Joey]] *[sort-hooks branch now withdrawn in favour of sort-package --s]* I briefly tried to turn *all* the current sort types into hook functions, and have some of them pre-registered, but decided that probably wasn't a good idea. That earlier version of the branch is also available for comparison: *[also withdrawn in favour of sort-package --s]* >> I wonder if IkiWiki would benefit from the concept of a "sortspec", like a [[ikiwiki/PageSpec]] but dedicated to sorting lists of pages rather than defining lists of pages? Rather than defining a sort-hook, define a SortSpec class, and enable people to add their own sort methods as functions defined inside that class, similarly to the way they can add their own pagespec definitions. --[[KathrynAndersen]] >>> [[!template id=gitbranch branch=smcv/ready/sort-package author="[[Simon_McVittie|smcv]]"]] >>> I'd be inclined to think that's overkill, but it wasn't very hard to >>> implement, and in a way is more elegant. I set it up so sort mechanisms >>> share the `IkiWiki::PageSpec` package, but with a `cmp_` prefix. Gitweb: >>> >>>> I agree it seems more elegant, so I have focused on it. >>>> >>>> I don't know about reusing `IkiWiki::PageSpec` for this. >>>> --[[Joey]] >>>>> Fair enough, `IkiWiki::SortSpec::cmp_foo` would be just >>>>> as easy, or `IkiWiki::Sorting::cmp_foo` if you don't like >>>>> introducing "sort spec" in the API. I took a cue from >>>>> [[ikiwiki/pagespec/sorting]] being a subpage of >>>>> [[ikiwiki/pagespec]], and decided that yes, sorting is >>>>> a bit like a pagespec :-) Which name would you prefer? --s >>>>>> `SortSpec` --[[Joey]] >>>>>>> [[Done]]. --s >>>> I would be inclined to drop the `check_` stuff. --[[Joey]] >>>>> It basically exists to support `title_natural`, to avoid >>>>> firing up the whole import mechanism on every `cmp` >>>>> (although I suppose that could just be a call to a >>>>> memoized helper function). It also lets sort specs that >>>>> *must* have a parameter, like >>>>> [[field|plugins/contrib/field/discussion]], fail early >>>>> (again, not so valuable). >>>>> >>>>>> AFAIK, `use foo` has very low overhead when the module is already >>>>>> loaded. There could be some evalation overhead in `eval q{use foo}`, >>>>>> if so it would be worth addressing across the whole codebase. >>>>>> --[[Joey]] >>>>>> >>>>>>> check_cmp_foo now dropped. --s >>>>> >>>>> The former function could be achieved at a small >>>>> compatibility cost by putting `title_natural` in a new >>>>> `sortnatural` plugin (that fails to load if you don't >>>>> have `title_natural`), if you'd prefer - that's what would >>>>> have happened if `title_natural` was written after this >>>>> code had been merged, I suspect. Would you prefer this? --s >>>>>> Yes! (Assuming it does not make sense to support >>>>>> natural order sort of other keys than the title, at least..) >>>>>> --[[Joey]] >>>>>>> Done. I added some NEWS.Debian for it, too. --s >>>> Wouldn't it make sense to have `meta(title)` instead >>>> of `meta_title`? --[[Joey]] >>>>> Yes, you're right. I added parameters to support `field`, >>>>> and didn't think about making `meta` use them too. >>>>> However, `title` does need a special case to make it >>>>> default to the basename instead of the empty string. >>>>> >>>>> Another special case for `title` is to use `titlesort` >>>>> first (the name `titlesort` is derived from Ogg/FLAC >>>>> tags, which can have `titlesort` and `artistsort`). >>>>> I could easily extend that to other metas, though; >>>>> in fact, for e.g. book lists it would be nice for >>>>> `field(bookauthor)` to behave similarly, so you can >>>>> display "Douglas Adams" but sort by "Adams, Douglas". >>>>> >>>>> `meta_title` is also meant to be a prototype of how >>>>> `sort=title` could behave in 4.0 or something - sorting >>>>> by page name (which usually sorts in approximately the >>>>> same place as the meta-title, but occasionally not), while >>>>> displaying meta-titles, does look quite odd. --s >>>>>> Agreed. --[[Joey]] >>>>>>> I've implemented meta(title). meta(author) also has the >>>>>>> `sortas` special case; meta(updated) and meta(date) >>>>>>> should also work how you'd expect them to (but they're >>>>>>> earliest-first, unlike age). --s >>>> As I read the regexp in `cmpspec_translate`, the "command" >>>> is required to have params. They should be optional, >>>> to match the documentation and because most sort methods >>>> do not need parameters. --[[Joey]] >>>>> No, `$2` is either `\w+\([^\)]*\)` or `[^\s]+` (with the >>>>> latter causing an error later if it doesn't also match `\w+`). >>>>> This branch doesn't add any parameterized sort methods, >>>>> in fact, although I did provide one on >>>>> [[field's_discussion_page|plugins/contrib/report/discussion]]. --s >>>> I wonder if it would make sense to add some combining keywords, so >>>> a sortspec reads like `sort="age then ascending title"` >>>> In a way, this reduces the amount of syntax that needs to be learned. >>>> I like the "then" (and it could allow other operations than >>>> simple combination, if any others make sense). Not so sure about the >>>> "ascending", which could be "reverse" instead, but "descending age" and >>>> "ascending age" both seem useful to be able to explicitly specify. >>>> --[[Joey]] >>>>> Perhaps. I do like the simplicity of [[KathrynAndersen]]'s syntax >>>>> from [[plugins/contrib/report]] (which I copied verbatim, except for >>>>> turning sort-by-`field` into a parameterized spec). >>>>> >>>>> If we're getting into English-like (or at least SQL-like) queries, >>>>> it might make sense to change the signature of the hook function >>>>> so it's a function to return a key, e.g. >>>>> `sub key_age { return -%pagemtime{$_[0]) }`. Then we could sort like >>>>> this: >>>>> >>>>> field(artistsort) or field(artist) or constant(Various Artists) then meta(titlesort) or meta(title) or title >>>>> >>>>> with "or" binding more closely than "then". Does this seem valuable? >>>>> I think the implementation would be somewhat more difficult. and >>>>> it's probably getting too complicated to be worthwhile, though? >>>>> (The keys that actually benefit from this could just >>>>> have smarter cmp functions, I think.) >>>>> >>>>> If the hooks return keys rather than cmp results, then we could even >>>>> have "lowercase" as an adjective used like "ascending"... maybe. >>>>> However, there are two types of adjective here: "lowercase" >>>>> really applies to the keys, whereas "ascending" applies to the "cmp" >>>>> result. Again, I think this is getting too complex, and could just >>>>> be solved with smarter cmp functions. >>>>> >>>>>> I agree. (Also, I think returning keys may make it harder to write >>>>>> smarter cmp functions.) --[[Joey]] >>>>> >>>>> Unfortunately, `sort="ascending mtime"` actually sorts by *descending* >>>>> timestamp (but`sort=age` is fine, because `age` could be defined as >>>>> now minus `ctime`). `sort=freshness` isn't right either, because >>>>> "sort by freshness" seems as though it ought to mean freshest first, >>>>> but "sort by ascending freshness" means put the least fresh first. If >>>>> we have ascending and descending keywords which are optional, I don't >>>>> think we really want different sort types to have different default >>>>> directions - it seems clearer to have `ascending` always be a no-op, >>>>> and `descending` always negate. >>>>> >>>>>> I think you've convinced me that ascending/descending impose too >>>>>> much semantics on it, so "-" is better. --[[Joey]] >>>>>>> I've kept the semantics from `report` as-is, then: >>>>>>> e.g. `sort="age -title"`. --s >>>>> Perhaps we could borrow from `meta updated` and use `update_age`? >>>>> `updateage` would perhaps be a more normal IkiWiki style - but that >>>>> makes me think that updateage is a quantity analagous to tonnage or >>>>> voltage, with more or less recently updated pages being said to have >>>>> more or less updateage. I don't know whether that's good or bad :-) >>>>> >>>>> I'm sure there's a much better word, but I can't see it. Do you have >>>>> a better idea? --s [Regarding the `meta title=foo sort=bar` special case] > I feel it sould be clearer to call that "sortas", since "sort=" is used > to specify a sort method in other directives. --[[Joey]] >> Done. --[[smcv]] ## speed I notice the implementation does not use the magic `$a` and `$b` globals. That nasty perl optimisation is still worthwhile: perl -e 'use warnings; use strict; use Benchmark; sub a { $a <=> $b } sub b ($$) { $_[0] <=> $_[1] }; my @list=reverse(1..9999); timethese(10000, {a => sub {my @f=sort a @list}, b => sub {my @f=sort b @list}, c => => sub {my @f=sort { b($a,$b) } @list}})' Benchmark: timing 10000 iterations of a, b, c... a: 80 wallclock secs (76.74 usr + 0.05 sys = 76.79 CPU) @ 130.23/s (n=10000) b: 112 wallclock secs (106.14 usr + 0.20 sys = 106.34 CPU) @ 94.04/s (n=10000) c: 330 wallclock secs (320.25 usr + 0.17 sys = 320.42 CPU) @ 31.21/s (n=10000) Unfortunatly, I think that c is closest to the new implementation. --[[Joey]] > Unfortunately, `$a` isn't always `$main::a` - it's `$Package::a` where > `Package` is the call site of the sort call. This was a showstopper when > `sort` was a hook implemented in many packages, but now that it's a > `SortSpec`, I may be able to fix this by putting a `sort` wrapper in the > `SortSpec` namespace, so it's like this: > > sub sort ($@) > { > my $cmp = shift; > return sort $cmp @_; > } > > which would mean that the comparison used `$IkiWiki::SortSpec::a`. > --s >> I've now done this. On a wiki with many [[plugins/contrib/album]]s >> (a full rebuild takes half an hour!), I tested a refresh after >> `touch tags/*.mdwn` (my tag pages contain inlines of the form >> `tagged(foo)` sorted by date, so they exercise sorting). >> I also tried removing sorting from `pagespec_match_list` >> altogether, as an upper bound for how fast we can possibly make it. >> >> * `master` at branch point: 63.72user 0.29system >> * `master` at branch point: 63.91user 0.37system >> * my branch, with `@_`: 65.28user 0.29system >> * my branch, with `@_`: 65.21user 0.28system >> * my branch, with `$a`: 64.09user 0.28system >> * my branch, with `$a`: 63.83user 0.36system >> * not sorted at all: 58.99user 0.29system >> * not sorted at all: 58.92user 0.29system >> >> --s > I do notice that `pagespec_match_list` performs the sort before the > filter by pagespec. Is this a deliberate design choice, or > coincidence? I can see that when `limit` is used, this could be > used to only run the pagespec match function until `limit` pages > have been selected, but the cost is that every page in the wiki > is sorted. Or, it might be useful to do the filtering first, then > sort the sub-list thus produced, then finally apply the limit? --s >> Yes, it was deliberate, pagespec matching can be expensive enough that >> needing to sort a lot of pages seems likely to be less work. (I don't >> remember what benchmarking was done though.) --[[Joey]] >>> We discussed this on IRC and Joey pointed out that this also affects >>> dependency calculation, so I'm not going to get into this now... --s Joey pointed out on IRC that the `titlesort` feature duplicates all the meta titles. I did that in order to sort by the unescaped version, but I've now changed the branch to only store that if it makes a difference. --s ## Documentation from sort-package branch ### advanced sort orders (conditionally added to [[ikiwiki/pagespec/sorting]]) * `title_natural` - Orders by title, but numbers in the title are treated as such, ("1 2 9 10 20" instead of "1 10 2 20 9") * `meta(title)` - Order according to the `\[[!meta title="foo" sortas="bar"]]` or `\[[!meta title="foo"]]` [[ikiwiki/directive]], or the page name if no full title was set. `meta(author)`, `meta(date)`, `meta(updated)`, etc. also work. ### Multiple sort orders (added to [[ikiwiki/pagespec/sorting]]) In addition, you can combine several sort orders and/or reverse the order of sorting, with a string like `age -title` (which would sort by age, then by title in reverse order if two pages have the same age). ### meta sortas parameter (added to [[ikiwiki/directive/meta]]) [in title] An optional `sort` parameter will be used preferentially when [[ikiwiki/pagespec/sorting]] by `meta(title)`: \[[!meta title="The Beatles" sort="Beatles, The"]] \[[!meta title="David Bowie" sort="Bowie, David"]] [in author] An optional `sortas` parameter will be used preferentially when [[ikiwiki/pagespec/sorting]] by `meta(author)`: \[[!meta author="Joey Hess" sortas="Hess, Joey"]] ### Sorting plugins (added to [[plugins/write]]) Similarly, it's possible to write plugins that add new functions as [[ikiwiki/pagespec/sorting]] methods. To achieve this, add a function to the IkiWiki::SortSpec package named `cmp_foo`, which will be used when sorting by `foo` or `foo(...)` is requested. The names of pages to be compared are in the global variables `$a` and `$b` in the IkiWiki::SortSpec package. The function should return the same thing as Perl's `cmp` and `<=>` operators: negative if `$a` is less than `$b`, positive if `$a` is greater, or zero if they are considered equal. It may also raise an error using `error`, for instance if it needs a parameter but one isn't provided. The function will also be passed one or more parameters. The first is `undef` if invoked as `foo`, or the parameter `"bar"` if invoked as `foo(bar)`; it may also be passed additional, named parameters.