> Does the plan change to INDEX if the condition would be:
> 1) ON p.icd10 = t.icd10
> 2) ON p.icd10 = t.icd10 OR p.icd10 = t.icd10

I think you meant
ON p.icd10 = t.icd10 OR p.icd10 = substring(t.icd10 from 1 for 3)


Sean