[jira] [Created] (SOLR-14931) Macros in appends/invariants parameters not getting expanded in Solrcloud

["Johannes Baiter (Jira)" <ji...@apache.org>]

Johannes Baiter created SOLR-14931:
--------------------------------------

             Summary: Macros in appends/invariants parameters not getting expanded in Solrcloud
                 Key: SOLR-14931
                 URL: https://issues.apache.org/jira/browse/SOLR-14931
             Project: Solr
          Issue Type: Bug
      Security Level: Public (Default Security Level. Issues are Public)
          Components: SolrCloud
    Affects Versions: 8.6.3, 7.6
            Reporter: Johannes Baiter


Macros in a request handler's {{appends}} or {{invariants}} parameter sets are not getting expanded when running in a SolrCloud setup.

In my case, I have a handler like the following:

{code:xml}
<requestHandler name="/myhandler" class="solr.SearchHandler">
  <lst name="defaults">
    <str name="q">some_field:"$${my_term}"</str>
    <str name="fl">term_defaults:'$${my_term},freq_defaults:docfreq(some_field, '$${my_term}')</str>
  </lst>
  <lst name="appends">
    <str name="fl">term_appends:'$${my_term}',freq_appends:docfreq(some_field, '$${my_term}')</str>
  </lst>
</requestHandler>
{code}

When querying the handler with `?my_term=foobar&echoParams=all`, something like this is the result:

{code:json}
{
    "response": {
        "docs": [
            {
                "term_defaults": "foobar",
                "term_appends": "${my_term}",
                "freq_appends": 0,
                "freq_defaults": 1
            }
        ],
        "maxScore": 13.244947,
        "numFound": 1,
        "start": 0
    },
    "responseHeader": {
        "QTime": 262091,
        "params": {
            "echoParams": "all",
            "fl": [
                "term_defaults:'foobar',freq_defaults:docfreq(some_field, 'foobar')",
                "term_appends:'foobar',freq_appends:docfreq(some_field, 'foobar')"
            ],
            "my_term": "foobar",
            "q": "some_field:\"foobar\"",
            "rows": "1"
        },
        "status": 0,
        "zkConnected": true
    }
}
{code}

As you can see, the macro in the {{appends}} {{fl}} parameter gets expanded in the {{responseHeader.params.fl}} field, but not in the actual document.

I believe the reason for this is the following:

* Setting of defaults/invariants/appends happens once before the request gets sent to the shards
* Here, macro expansion happens, i.e. the shards get the fully expanded parameters
* On the shards, once again, defaults/invariants/appends are set (https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/handler/RequestHandlerBase.java#L209)
* However, this time *macros are not expanded* (https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/request/json/RequestUtil.java#L151-L161)
* For {{defaults}} parameters, this doesn't break anything, since the (expanded) parameter from the request takes precedence over the server-supplied value.
* However, for {{appends}}, both the expanded and the unexpanded version are now set, while for {{invariants}} the expanded value is removed from the params

I think the easy/obvious fix for this would be not to set {{defaults}}/{{invariants}}/{{appends}} parameters twice, i.e. disable it when {{isShard=true}}, just like macro expansion, but I don't have the full picture if that might not break something else.

Here's the Twitter thread where I rubber-ducked through this issue: https://twitter.com/jbaiter_/status/1316023733576843272



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