For a main text query that will include a separate Parametric Search query, the Compound Index Fields setting (here) may need to be updated. These fields are part of the standard Metamorph Inverted search index, but can help with secondary queries after the main text search, as well as improving Fast Result Counts.
For example, the following query searches both document text as well as a Parametric Search field:
backyard gardening infield:Price<24
The text search is "backyard gardening", which will search the Index Fields. Since a separate search for "Price less than 24" is also being done, Price should be added to Compound Index Fields.
Note that Compound Index Fields can only improve performance
in conjunction with a separate text search. If there is no main text
search (i.e. the query infield:Price<24
alone), this part of the
index cannot be used, and a separate index may need to be created (see
below).
It is not always necessary to add every possible field that might be searched to the Compound Index Fields. Adding too many can actually decrease search performance, as more fields require more RAM. A search against a field that is not in Compound Index Fields can still be performed; it may just be slower, and may not return as accurate a result count under Fast Result Counts.