Solr query with space, only (#q=%20) stalls

Question

I have a web-based frontend (localhost, currently) that uses Ajax to query Solr.

It's working well, but if I submit a single space (nothing else) in the input/search box, the URL in the browser shows

...#q=%20

and in that circumstance I get a 400 error, and my web page stalls (doesn't refresh), apparently waiting for a response from Solr.

By comparison, if I submit a semicolon (;) rather than a space, then the page immediately refreshes, albeit with no results (displaying 0 to 0 of 0; expected).

My question is what is triggering the " " (%20) query fault in Solr, and how do I address it in solrconfig.xml?

Answer 1

Update. This solrconfig.xml entry resolved the q=%20 issue I described.

<requestHandler name="/select" class="solr.SearchHandler">
  <lst name="defaults">
    <str name="echoParams">explicit</str>
    <int name="rows">10</int>
    <str name="hl">off</str>
    <str name="wt">html</str> 
    <str name="df">query</str>
    <!-- *** ADDITION: *** -->
    <str name="defType">edismax</str>
  </lst>
</requestHandler>

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Note: development code, dummy data.

Before: https://www.youtube.com/watch?v=GhkA4XlqWds&list=PLTtHvbtVBhk6zAqSJ3A1-shsD_h5i3IuP&index=2

After: https://www.youtube.com/watch?v=507DdPOx1xA&list=PLTtHvbtVBhk6zAqSJ3A1-shsD_h5i3IuP&index=1

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Additional discussion (reddit:Solr): https://old.reddit.com/r/Solr/comments/kt97ql/solr_query_with_space_only_q20_gives_error/