Fastest way to get the length of the intersection of two text arrays in PostgreSQL
You say you're looking for "Jaccard Similarity between two arrays"

You may consider MadLib which provides this as dist_jaccard()


  Jaccard distance between two varchar vectors treated as sets.

You may want to try it without STRICT. That may be slowing it down.
You may want to use INTERSECT ALL Especially if you know you don't have dupes in $1.
As Craig Ringer said in the comments you may want out intarray and consider using &amp;.


To give a more accurate answer here,


What are the datatypes?
How many elements are we talking about on each array?
How much exclusion does the INTERSECT provide?