diff options
author | Jonas Smedegaard <dr@jones.dk> | 2010-08-27 10:01:58 +0200 |
---|---|---|
committer | Jonas Smedegaard <dr@jones.dk> | 2010-08-27 10:01:58 +0200 |
commit | f398ad035b973608d380c9939ea845d8e2a0cdc2 (patch) | |
tree | 1ba1a0c94e375ab8ed609eaa57a542c6b87de5a8 /doc/todo/allow_plugins_to_add_sorting_methods.mdwn | |
parent | 958e5735c946263a111420fe47abe58782581e8c (diff) | |
parent | 6d213a0c739d5b34357b01a616f99197eeba6ad9 (diff) |
Merge branch 'master' of git://git.ikiwiki.info
Diffstat (limited to 'doc/todo/allow_plugins_to_add_sorting_methods.mdwn')
-rw-r--r-- | doc/todo/allow_plugins_to_add_sorting_methods.mdwn | 304 |
1 files changed, 304 insertions, 0 deletions
diff --git a/doc/todo/allow_plugins_to_add_sorting_methods.mdwn b/doc/todo/allow_plugins_to_add_sorting_methods.mdwn new file mode 100644 index 000000000..b523cd19f --- /dev/null +++ b/doc/todo/allow_plugins_to_add_sorting_methods.mdwn @@ -0,0 +1,304 @@ +[[!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 --[[Joey]] + +*[sort-hooks branch now withdrawn in favour of sort-package --s]* + +I briefly tried to turn *all* the current sort types into hook functions, and +have some of them pre-registered, but decided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 +That earlier version of the branch is also available for comparison: + +*[also withdrawn in favour of sort-package --s]* + +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: +>>> <http://git.pseudorandom.co.uk/smcv/ikiwiki.git?a=shortlog;h=refs/heads/sort-package> + +>>>> 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. |