change in the Standard Query Parser behavior when migrating from Solr 5 to 7.

[Piyush Kumar Nayak]

we have recently upgraded from Solr5 to Solr7. I'm running into a change of 
behavior that I cannot fathom.
For the term "test3" Solr7 splits the numeric and alphabetical components and 
does a simple term search while Solr 5 did a phrase search.
----------------------------------------------------------------------------------------------------------------------------------------------
lucene/solr-spec: 7.2.1
http://localhost:8991/solr/solr4/select?q=test3&fq=test&wt=json&indent=true&debugQuery=true

"debug":{
    "rawquerystring":"test3",
    "querystring":"test3",
    "parsedquery":"contents:test contents:3",
    "parsedquery_toString":"contents:test contents:3",

----------------------------------------------------------------------------------------------------------------------------------------------
lucene/solr-spec 5.2.1
http://localhost:8989/solr/solr4/select?q=test3&fq=test&wt=json&indent=true&debugQuery=true

"debug":{
    "rawquerystring":"test3",
    "querystring":"test3",
    "parsedquery":"PhraseQuery(contents:\"test 3\")",
    "parsedquery_toString":"contents:\"test 3\"",
----------------------------------------------------------------------------------------------------------------------------------------------


I've not been able to find any mention of in the release notes or user guide at:
https://lucene.apache.org/solr/guide/7_3/major-changes-in-solr-7.html
https://lucene.apache.org/solr/guide/7_3/major-changes-from-solr-5-to-solr-6.html

Also, the fieldType name="text" in the schema.xml for the cores in both the 
versions of Solr are identical.
I'd appreciate any pointers that can help with explaining this change.

Thanks,
Piyush.