ctargett commented on a change in pull request #113:
URL: https://github.com/apache/solr/pull/113#discussion_r625802740
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File path: solr/solr-ref-guide/src/common-query-parameters.adoc
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@@ -278,9 +278,12 @@ If you do not define the `wt` parameter in your queries,
JSON will be returned a
Solr caches the results of all queries and filter queries by default. To
disable result caching, set the `cache=false` parameter.
-You can also use the `cost` option to control the order in which non-cached
filter queries are evaluated. This allows you to order less expensive
non-cached filters before expensive non-cached filters.
+You can also use the `cost` option to provide a hint as to the order in which
non-cached filter queries are evaluated.
+This allows you to order less expensive non-cached filters before expensive
non-cached filters.
+At the Lucene layer, this maps to `TwoPhaseIterator.matchCost` if the query
has a TPI.
-For very high cost filters, if `cache=false` and `cost>=100` and the query
implements the `PostFilter` interface, a Collector will be requested from that
query and used to filter documents after they have matched the main query and
all other filter queries. There can be multiple post filters; they are also
ordered by cost.
+*Post Filters*: For very high cost filters, if `cache=false` _and_
`cost>=100`, _and_ the query implements the `PostFilter` interface, a Collector
will be requested from that query and used to filter documents after they have
matched the main query and all other filter queries.
Review comment:
This is a bigger issue than you probably intend to deal with here, and I
recognize you're editing an existing sentence, but I want to mention it as
something to consider - there are 5 total mentions of PostFilters in the ref
guide and none of them define what a "post filter" is or when or how or what
specifically implements a "PostFilter interface".
I mention it because I was looking at this section the other day and
wondered how I would be able to know if my query implements a PostFilter - is
it a thing? a method? a backend default? Here and following we're emphasizing
the relationship between the `cache` and `cost` params and a PostFilter and
this expects the reader to know what it is. But we've never defined it anywhere.
As I said it's a bigger problem than your small edit, but since I don't know
what it is in order to define it anywhere, maybe you'd have time to improve
this gap?
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