Understanding Solr Function Query Performance

Question

I'm working with "edismax" and "function-query" parsers in Solr and have difficulty in understanding whether the query time taken by "function-query" makes sense. The query I'm trying to optimize looks as follows:

q={!func sum($q1,$q2,$q3)} where q1,q2,q3 are edismax queries.

The QTime returned by edismax queries takes well under 50ms but it seems that function-query is the rate determining step since combined query above takes around 200-300ms. I also analyzed the performance of function query using only constants.

The QTime results for different q are as follows:

• 097ms for q={!func} sum(10,20)

• 109ms for q={!func} sum(10,20,30)

• 127ms for q={!func} sum(10,20,30,40)

• 145ms for q={!func} sum(10,20,30,40,50)

Does this trend make sense? Are function-queries expected to be this slow?

What makes edismax queries so much faster?

What can I do to optimize my original query (which has edismax subqueries q1,q2,q3) to work under 100ms?

Answer 1

func query enumerates all docs, thus it doesn't provide any selectivity. You probably don't need to evaluate it on docs, which doesn't match dismaxes eg

q=+{!v=$q1} +{!v=$q2} +{!v=$q3} {!func sum($q1,$q2,$q3)}