Draft patch... just a few lines of code as proof-of-concept.

Relevant output looks like so

"facet_counts":{
"facet_queries":{},
"facet_fields":{
"cat":{
"camera":0,
"card":0}}}}

For the following URL:
http://localhost:8983/solr/select/?q=a&rows=0&facet=on&facet.field=cat&facet.prefix=ca&wt=json&indent=on

Only works for the filter method of faceting, not the FieldCache method.
Would be simple to add though... do a binary search for the prefix in the StringIndex and start there.

Comments? Is the external API right? facet.prefix (and per-field f.cat.facet.prefix)
I had considered a more generic facet.field.terms=ca* but Erik's comment about client escaping make me realize it's simpler on both sides to just say "prefix".

Full patch w/ tests attached.

This version also implements facet.prefix for the FieldCache method. It also lowers the memory used per-request for that method (because int[] count is smaller since we know the max number of terms beforehand that match the prefix). A binary search is used to find the start and end terms for the prefix.

Yonik - I've given this a try - works very well.

committed.

This bug was modified as part of a bulk update using the criteria...

• Marked ("Resolved" or "Closed") and "Fixed"
• Had no "Fix Version" versions
• Was listed in the CHANGES.txt for 1.2

The Fix Version for all 39 issues found was set to 1.2, email notification
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For a list of all the issues modified, search jira comments for this
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