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< h1 > Plugin – lektor-limit-dependencies 0.1< / h1 >
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< p > Lektor plugin to limit dependencies created by queries< p >
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< h4 > Meta< / h4 >
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< p > < strong > Version:< / strong > 0.1< / p >
< p > < strong > Author:< / strong >
< a href = "mailto:dairiki@dairiki.org" > Jeff Dairiki< / a >
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< h4 > Tags< / h4 >
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< a href = "../tag/build-optimization/" > build optimization< / a > ,
< a href = "../tag/Jinja-filters/" > Jinja filters< / a > ,
and
< a href = "../tag/setup-env/" > setup-env< / a >
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View < a href = "../tags/" class = "ref" > all tags< / a > .
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< div class = "col-sm-9 doc-styling" >
< h2 > Project Description< / h2 >
< h1 > Lektor Limit Dependencies< / h1 >
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< p > < a href = "https://pypi.org/project/lektor-limit-dependencies/" rel = "nofollow" > < img src = "https://img.shields.io/pypi/v/lektor-limit-dependencies.svg" alt = "PyPI version" > < / a >
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< a href = "https://github.com/dairiki/lektor-limit-dependencies/blob/master/LICENSE" rel = "nofollow" > < img src = "https://img.shields.io/github/license/dairiki/lektor-limit-dependencies" alt = "GitHub license" > < / a >
< a href = "https://github.com/dairiki/lektor-limit-dependencies" rel = "nofollow" > < img src = "https://github.com/dairiki/lektor-limit-dependencies/workflows/Tests/badge.svg" alt = "GitHub Actions (Tests)" > < / a > < / p >
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< p > This is an experimental < a href = "https://www.getlektor.com/" rel = "nofollow" > Lektor< / a > plugin which aims to provide tools (or,
at least, a tool) to help keep Lektor’
control.< / p >
< h2 > Introduction< / h2 >
< h3 > Motivating Example< / h3 >
< p > Suppose that you would like to list the three most recent blog posts
in the sidebar of your Lektor-based site. This can be done by adding
something like to your site base template:< / p >
< pre > < span class = "p" > < < / span > < span class = "nt" > h3< / span > < span class = "p" > > < / span > Recent Posts< span class = "p" > < /< / span > < span class = "nt" > h3< / span > < span class = "p" > > < / span >
< span class = "p" > < < / span > < span class = "nt" > ul< / span > < span class = "p" > > < / span >
< span class = "cp" > {%< / span > < span class = "k" > for< / span > < span class = "nv" > post< / span > < span class = "k" > in< / span > < span class = "nv" > site.query< / span > < span class = "o" > (< / span > < span class = "s1" > ' /blog' < / span > < span class = "o" > )< / span > < span class = "nv" > .order_by< / span > < span class = "o" > (< / span > < span class = "s1" > ' -pub_date' < / span > < span class = "o" > )< / span > < span class = "nv" > .limit< / span > < span class = "o" > (< / span > < span class = "m" > 3< / span > < span class = "o" > )< / span > < span class = "cp" > %}< / span >
< span class = "p" > < < / span > < span class = "nt" > li< / span > < span class = "p" > > < < / span > < span class = "nt" > a< / span > < span class = "na" > href< / span > < span class = "o" > =< / span > < span class = "s" > " < / span > < span class = "cp" > {{< / span > < span class = "nv" > post< / span > < span class = "o" > |< / span > < span class = "nf" > url< / span > < span class = "cp" > }}< / span > < span class = "s" > " < / span > < span class = "p" > > < / span > < span class = "cp" > {{< / span > < span class = "nv" > post.title< / span > < span class = "cp" > }}< / span > < span class = "p" > < /< / span > < span class = "nt" > a< / span > < span class = "p" > > < /< / span > < span class = "nt" > li< / span > < span class = "p" > > < / span >
< span class = "cp" > {%< / span > < span class = "k" > endfor< / span > < span class = "cp" > %}< / span >
< span class = "p" > < /< / span > < span class = "nt" > ul< / span > < span class = "p" > > < / span >
< / pre >
< p > This is not without drawbacks, however. To sort the post query by
date, Lektor iterates through < em > < strong > all< / strong > < / em > of the blog’
them. In so doing, it records all of the blog posts as dependencies
< em > of every page on which this most-recent-post query is used< / em > . If this
is in the sidebar of every page on your site, < em > now every page on your
site will be rebuilt whenever any blog post at all< / em > (not just one of
the three most recent posts) < em > is edited< / em > .< / p >
< p > Technically, it is true that all pages now depend on all posts. You
might well edit the < code > pub_date< / code > of one of your older posts, such that
it should now appear in the most-recent listing. However, it is not
true that all pages need to be rebuilt for < em > any< / em > edit of any post.
Unfortunately, Lektor’
enough to be able to express details about < em > how< / em > pages are
dependent on other pages; it only records that they < em > are< / em >
dependent, so Lektor has no option but to rebuild everything.< / p >
< h3 > A Solution?< / h3 >
< p > This plugin introduces a Jinja filter, < code > limit_dependencies< / code > . It
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expects, as input, a Lektor < a href = "https://www.getlektor.com/docs/api/db/query/" title = "Lektor documentation on the Query class" rel = "nofollow" > query< / a > instance. It iterates through the
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input query, and returns a new query instance which will yield the
same results. While it is doing its iteration, it — essentially —
monkey-patches Lektor’
from recording any dependencies.< / p >
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< p > At the end, < code > limit_dependencies< / code > records one dependency on a < a href = "https://www.getlektor.com/docs/api/db/obj/#virtual-source-objects" title = "Lektor documentation on Virtual Source Objects" rel = "nofollow" > virtual
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source object< / a > which depends only on the sequence of the identities
of the records in the query result. (Lektor provides a means by which
virtual source objects can report checksums. The
dependency tracking mechanism records those checksums, and will
trigger a rebuild should the checksum change. < code > Limit_dependencies< / code >
generates a virtual source object whose checksum depends on the
sequence of identities in the query result.)< / p >
< p > In the above example, this is exactly what we want. We only want to
trigger a rebuild if the order or composition of the most-recent three
posts changes. (Or if any of their titles change. Note that this
gets covered, too, since when the resulting query is iterated over in
the < code > {% for %}< / code > loop, dependencies will be recorded on the three
most-recent posts.)< / p >
< p > Thus, the example above, if replaced by:< / p >
< pre > < span class = "p" > < < / span > < span class = "nt" > h3< / span > < span class = "p" > > < / span > Recent Posts< span class = "p" > < /< / span > < span class = "nt" > h3< / span > < span class = "p" > > < / span >
< span class = "p" > < < / span > < span class = "nt" > ul< / span > < span class = "p" > > < / span >
< span class = "cp" > {%< / span > < span class = "k" > for< / span > < span class = "nv" > post< / span > < span class = "k" > in< / span > < span class = "nv" > site.query< / span > < span class = "o" > (< / span > < span class = "s1" > ' /blog' < / span > < span class = "o" > )< / span > < span class = "nv" > .order_by< / span > < span class = "o" > (< / span > < span class = "s1" > ' -pub_date' < / span > < span class = "o" > )< / span > < span class = "nv" > .limit< / span > < span class = "o" > (< / span > < span class = "m" > 3< / span > < span class = "o" > )|< / span > < span class = "nf" > limit_dependencies< / span > < span class = "cp" > %}< / span >
< span class = "p" > < < / span > < span class = "nt" > li< / span > < span class = "p" > > < < / span > < span class = "nt" > a< / span > < span class = "na" > href< / span > < span class = "o" > =< / span > < span class = "s" > " < / span > < span class = "cp" > {{< / span > < span class = "nv" > post< / span > < span class = "o" > |< / span > < span class = "nf" > url< / span > < span class = "cp" > }}< / span > < span class = "s" > " < / span > < span class = "p" > > < / span > < span class = "cp" > {{< / span > < span class = "nv" > post.title< / span > < span class = "cp" > }}< / span > < span class = "p" > < /< / span > < span class = "nt" > a< / span > < span class = "p" > > < /< / span > < span class = "nt" > li< / span > < span class = "p" > > < / span >
< span class = "cp" > {%< / span > < span class = "k" > endfor< / span > < span class = "cp" > %}< / span >
< span class = "p" > < /< / span > < span class = "nt" > ul< / span > < span class = "p" > > < / span >
< / pre >
< p > will work in a much more efficient and sane manner. Pages will be
rebuilt only if there are changes in the order, composition or content
of the three most recent posts.< / p >
< h2 > Installation< / h2 >
< p > Add lektor-limit-dependencies to your project from command line:< / p >
< pre > < code > lektor plugins add lektor-limit-dependencies
< / code > < / pre >
< p > See < a href = "https://www.getlektor.com/docs/plugins/" rel = "nofollow" > the Lektor plugin documentation< / a > for more information.< / p >
< h2 > Author< / h2 >
< p > Jeff Dairiki < a href = "mailto:dairiki@dairiki.org" > dairiki@dairiki.org< / a > < / p >
< h2 > Changelog< / h2 >
< h3 > Release 0.1 (2021-02-05)< / h3 >
< p > No code changes.< / p >
< p > Update development status classifier to " stable" .< / p >
< p > Test under python 3.9. Stop testing under 3.5.< / p >
< h3 > Release 0.1a1 (2020-05-19)< / h3 >
< p > Initial release.< / p >
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