Apache Solr Reference Guide Covering Apache Solr 6.0

post-processors
However executing a processor only on the forwarding nodes is a great way of distributing an expensive
computation such as de-duplication across a SolrCloud cluster by sending requests randomly via a load
balancer. Otherwise the expensive computation is repeated on both the leader and replica nodes.
Pre-processors and Atomic Updates
Because DistributedUpdateProcessor is responsible for processing Atomic Updates into full documents
on the leader node, this means that pre-processors which are executed only on the forwarding nodes
can only operate on the partial document. If you have a processor which must process a full document
then the only choice is to specify it as a post-processor.
Using custom chains
update.chain request parameter
The update.chain parameter can be used in any update request to choose a custom chain which has been
configured in solrconfig.xml. For example, in order to choose the "dedupe" chain described in a previous section,
one can issue the following request:
update.chain
curl
"http://localhost:8983/solr/gettingstarted/update/json?update.chain=dedupe&commit=tr
ue" -H 'Content-type: application/json' -d '
[
{
"name" : "The Lightning Thief",
"features" : "This is just a test",
"cat" : ["book","hardcover"]
},
{
"name" : "The Lightning Thief",
"features" : "This is just a test",
"cat" : ["book","hardcover"]
}
]'
The above should dedupe the two identical documents and index only one of them.
processor & post-processor request parameters
We can dynamically construct a custom update request processor chain using the "processor" and
"post-processor" request parameters. Multiple processors can be specified as a comma-separated value for
these two parameters. For example:
Apache Solr Reference Guide 6.0
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