Decoding the Solr More Like This Query Parameters
This section details the query parameters that are sent through to the Solr server when a More Like This query is performed, what they mean and the Panl properties which may affect the implementation.
Both of the implementations included in the Panl server will generate Solr queries with predominantly the same parameters, however their format is different.
The main difference is that the MoreLikeThis Request Handler passes every parameter through as a URL query parameter, whilst the MoreLikeThis Query Parser encodes the parameters within curly braces - i.e. '{}', delimited by spaces
MoreLikeThis Request Handler
For the request handler, the query string will be of the form:
mlt=true&qt=/mlt&mlt.fl=title,author,series,genre&mlt.mintf=0&mlt.mindf=0&q=id:2&ml
t.minwl=0&mlt.interestingTerms=none&mlt.match.include=false&shards=shard1&shards.pr
eference=replica.location:local&rows=5&fl=id,author,title,genre,series
MoreLikeThis Query Parser
For the query parser, the query string will be of the form:
qt=/select&q={!mlt+qf=title,author,series,genre+mintf=0 mindf=0 minwl=0}2&rows=5&fl
=id,author,title,genre,series
Translating The Parameters
The MLT Request Handler passes through the URL key value pair parameters prefixed with mlt., where the Query Parser encodes the parameters into the query parameter (i.e. 'q').
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Query Parameter Mapping and Availability
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Panl configuration parameter |
Request Handler |
Query Parser |
Notes |
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panl.mlt.enable |
true |
true |
Must be set to true to enable MLT functionality |
|
panl.mlt.handler |
/mlt |
/select |
Can be configured to any of the Solr handlers which are defined. |
|
panl.mlt.type |
mlt |
select |
Can only be one of the two values. |
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panl.mlt.numretries |
6 |
N/A |
Only applicable to the Request Handler, will be ignored for the Query Parser |
|
Panl configuration parameter |
Request Handler URL Parameter |
Query Parser Equivalent URL Parameter |
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panl.mlt.fl |
mlt.fl |
N/A (use panl.mlt.qf instead) |
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panl.mlt.mintf |
mlt.mintf |
mintf |
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panl.mlt.mindf |
mlt.mindf |
mindf |
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panl.mlt.mindf |
mlt.maxdf |
maxdf |
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panl.mlt.maxdfpct |
mlt.maxdfpct |
N/A |
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panl.mlt.minwl |
mlt.minwl |
minwl |
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panl.mlt.maxwl |
mlt.maxwl |
maxwl |
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panl.mlt.maxqt |
mlt.maxqt |
maxqt |
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panl.mlt.maxntp |
mlt.maxntp |
maxntp |
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panl.mlt.boost |
mlt.boost |
boost |
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panl.mlt.qf |
N/A (use panl.mlt.fl instead) |
qf |
|
panl.mlt.interestingTerms |
mlt.interestingTerms |
N/A |
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panl.mlt.match.include |
mlt.match.include |
N/A |
|
panl.mlt.match.offset |
mlt.match.offset |
N/A |
qt=
This is the query handler that the Solr server will use to handle the incoming request.
If not set, it defaults to /select - and in the previous section on decoding the Solr query parameters, this is not included as a parameter and uses this default).
MoreLikeThis Request Handler
In the request handler, the qt parameter is set to /mlt which will hit the defined Solr MoreLikeThis Request Handler at the URL:
MoreLikeThis Query Parser
For the query parser implementation, it is explicitly set, although not necessary. This was implemented in case a separate select query handler was registered and used. This will translate[51] to the URL of:
q=
This is the Solr query parameter - i.e. the keyword search parameter
MoreLikeThis Request Handler
The query will ALWAYS be the Solr unique key field (in this instance id) and the value of the unique Solr document id.
MoreLikeThis Query Parser
The query is specially formulated inside curly braces with all of the options without the mlt. query parameter prefix.
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