diff options
| -rw-r--r-- | doc/todo/dependency_types.mdwn | 57 |
1 files changed, 46 insertions, 11 deletions
diff --git a/doc/todo/dependency_types.mdwn b/doc/todo/dependency_types.mdwn index 01205f178..d3ffdf7b2 100644 --- a/doc/todo/dependency_types.mdwn +++ b/doc/todo/dependency_types.mdwn @@ -236,6 +236,9 @@ sigh. >> dependency graph. This can lead to situations where the result is just not >> well defined. This is what I was trying to get at above. -- [[Will]] +>>> Hmm, I'm not seeing cycles be a problem, at least with the current +>>> pagespec terms. --[[Joey]] + ---- ### Link dependencies @@ -322,6 +325,17 @@ can indirectly influence what pages a pagespec matches. > is not very formal and I suspect will lead to problems. Something like "The set of pages matched by the globs in the pagespec" might be closer? > --[[Will]] +>> I appreciate the formalism! +>> +>> Only existing pages need to be in these sets, because if a page is added +>> in the future, the existing dependency code will always test to see +>> if it matches. So it will be in the maching set (or not) at that point. +>> +>> The problem with your definition of direct influence set seems to be +>> that it doesn't allow `link()` and `title()` to have as an indirect +>> influence, the page that matches. But I'm quite sure we need those. +>> --[[Joey]] + #### Examples * The pagespec "created_before(foo)" has an influence list that contains foo. @@ -337,9 +351,8 @@ can indirectly influence what pages a pagespec matches. * The pagespec "title(foo)" has an influence list that contains every page that currently matches it. A change to any matching page can change its - title. Why is that considered an indirect influence? Well, the pagespec - might be used in a presence dependency, and so its title changing - would not directly affect the dependency. + title, making it not match any more, and so the list is needed due to the + removal problem. * The pagespec "backlink(index)" has an influence list that contains index (because a change to index changes the backlinks). @@ -353,6 +366,10 @@ can indirectly influence what pages a pagespec matches. >> 'done' to include a link to 'done', then it will now match... or is that considered a >> 'direct match'? -- [[Will]] +>>> The regular dependency calculation code will check if every changed +>>> page matches every dependency. So it will notice the link was added. +>>> --[[Joey]] + #### Low-level Calculation One way to calculate a pagespec's influence would be to @@ -404,13 +421,29 @@ successful match, we get the right result. #### High-level Calculation and Storage -Calculating the full influence list for a pagespec requires trying to match -it against every page in the wiki. - -I'd like to avoid doing such expensive matching redundantly. So add a -`pagespec_match_all`, which returns a list of all pages in the whole -wiki that match the pagespec, and also adds the pagespec as a dependency, -and while it's at it, calculates and stores the influence list. +Naively calculating the full influence list for a pagespec requires trying +to match it against every page in the wiki. I'd like to avoid doing such +expensive matching redundantly. + +It may be possible, for some types of pagespecs, to just try matching a +single, arbitrary page against it, and know the full influence list has +been obtained. It seems to be that case that if a pagespec has any +influences, matching any page will return at least one. So if none are +returned, we can skip trying other pages. + +If the influence list does not include the page that was tried, we know +that the pagespec does not things like `link()` and `title()`, that are +influenced by the page's own content. So it *might* be safe to not try +matching any more pages in this case too. I think it would work for all +current pagespec terms. There might be a hypothetical term where this +optimisation doesn't work. We could add a special case to ensure it can +work: If a term declares it is unfluenced by "", then it means it is +always influenced by the matching page. + +Anyway, this seems worth doing: Add a `pagespec_match_all`, which returns a +list of all pages in the whole wiki that match the pagespec, and also adds +the pagespec as a dependency, and while it's at it, calculates and stores +the influence list. It could have an optional sort parameter, and limit parameter, to control how many items to return and the sort order. So when inline wants to @@ -435,7 +468,7 @@ it's calculated more smartly, and is added automatically. > I've implemented influence calculation in `add_depends`. As expected, > it means rather a lot more work, and makes some things much slower. -> Optimisation via `pagespec_match_depends` next.. --[[Joey]] +> Optimisations next.. --[[Joey]] #### Influence types @@ -448,3 +481,5 @@ type. Etc. > allow significant computational savings, but I suspect will be tricky > to implement. -- [[Will]] +>> It was actually really easy to implement it, assuming I picked the right +>> dependency types of course. --[[Joey]] |