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[git.ikiwiki.info.git] / doc / todo / dependency_types.mdwn

diff --git a/doc/todo/dependency_types.mdwn b/doc/todo/dependency_types.mdwn
index 01205f178a16c77d53285eacfb75965bbb53c31a..97cff97c53b4d13b95635da5b9d163fc6239d19a 100644 (file)
--- 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]]
 
 >> 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
 ---- 
 
 ### Link dependencies


@@ -276,7 +279,7 @@ One way to fix this is to include with each dependency, a list of pages
 that currently match it. If the list changes, the dependency is triggered.
 
 Should be doable, but may involve more work than
 that currently match it. If the list changes, the dependency is triggered.
 
 Should be doable, but may involve more work than

-currently. Consider that a dependency on "bugs/*" currently
+currently. Consider that a dependency on `bugs/*` currently

 is triggered by just checking until *one* page is found to match it.
 But to store the list, *every* page would have to be tried against it.
 Unless the list can somehow be intelligently updated, looking at only the
 is triggered by just checking until *one* page is found to match it.
 But to store the list, *every* page would have to be tried against it.
 Unless the list can somehow be intelligently updated, looking at only the


@@ -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]]
 
 > 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.
 #### 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
 
 * 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).
 
 * 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]]
 
 >> '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
 #### Low-level Calculation
 
 One way to calculate a pagespec's influence would be to


@@ -400,17 +417,36 @@ Given that, the `backlink` will always be evalulated, and will put index
 onto the influence list. If we combine the influences from each
 successful match, we get the right result.
 
 onto the influence list. If we combine the influences from each
 successful match, we get the right result.
 

-> This is implemented, seems to work ok. --[[Joey]] 
+> This is implemented, seems to work ok. --[[Joey]]

 
 

-#### High-level Calculation and Storage
+> `or` short-circuits too, but the implementation correctly uses `|`,
+> which I assume is what you meant. --[[smcv]]

 
 

-Calculating the full influence list for a pagespec requires trying to match
-it against every page in the wiki. 
+#### High-level Calculation and Storage

 
 

-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
 
 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 +471,7 @@ 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.
 
 > 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
 
 
 #### Influence types
 


@@ -448,3 +484,5 @@ type. Etc.
 > allow significant computational savings, but I suspect will be tricky
 > to implement. -- [[Will]]
 
 > 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]]