Details
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New Feature
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Status: Resolved
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Major
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Resolution: Won't Fix
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New, Patch Available
Description
If you need to analyze the root cause of a query's failure to match some document, you can use the Weight.explain() API. If you want to do some gross analysis of a whole batch of queries, say scraped from a log, that once matched, but no longer do, perhaps after some refactoring or other large-scale change, the Explanation isn't very good for that. You can try parsing its textual output, which is pretty regular, but instead I found it convenient to add some boolean structure to Explanation, and use that to find failing leaves on the Explanation tree, and report only those.
This patch adds a "condition" to each Explanation, which can be REQUIRED, OPTIONAL, PROHIBITED, or NONE. The conditions correspond in obvious ways to the Boolean Occur, except for NONE, which is used to indicate a node which can't be further decomposed. It adds new Explanation construction methods for creating Explanations with conditions (defaulting to NONE with the existing methods).
Finally Explanation.getFailureCauses() returns a list of Strings that are the one-line explanations of the failing queries that, if some of them had succeeded, would have made the original overall query match.