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https://issues.apache.org/jira/browse/SOLR-7097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14328574#comment-14328574
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Noble Paul commented on SOLR-7097:
----------------------------------
documents are always streamed out . So we only handle one document at a time.
So , Solr cannot give a mechanism to modify previous docs.
However, it is possible for the transformer to cache docs .
The API does not let you do that today , it is pretty rigid.
The current method is like this
{code:java}
public abstract void transform(SolrDocument doc, int docid) throws IOException;
{code}
If it was like the following
{code:java}
public abstract List<SolrDocument> transform(SolrDocument doc, int docid)
throws IOException;
{code}
Then you could return an empty list when you want to cache stuff. or you can
spit out multiple docs all at once.
But the challenge is , your {{rows}} parameter will be totally screwed. you may
specify rows=10 and you may get 100 in return or none at all
> Update other Document in DocTransformer
> ---------------------------------------
>
> Key: SOLR-7097
> URL: https://issues.apache.org/jira/browse/SOLR-7097
> Project: Solr
> Issue Type: Improvement
> Reporter: jefferyyuan
> Priority: Minor
> Labels: searcher, transformers
>
> Solr DocTransformer is good, but it only allows us to change current
> document: add or remove, update fields.
> It would be great if we can update other document(previous especially) , or
> better we can delete doc(especially useful during test) or add doc in
> DocTransformer.
> User case:
> We can use flat group mode(group.main=true) to put parent and child close to
> each other(parent first), then we can use DocTransformer to update parent
> document when access its child document.
> Some thought about Implementation:
> org.apache.solr.response.TextResponseWriter.writeDocuments(String,
> ResultContext, ReturnFields)
> when cachMode=true, in the for loop, after transform, we can store the
> solrdoc in a list, write these doc at the end.
> cachMode = req.getParams().getBool("cachMode", false);
> SolrDocument[] cachedDocs = new SolrDocument[sz];
> for (int i = 0; i < sz; i++) {
> SolrDocument sdoc = toSolrDocument(doc);
> if (transformer != null) {
> transformer.transform(sdoc, id);
> }
> if(cachMode)
> {
> cachedDocs[i] = sdoc;
> }
> else{
> writeSolrDocument( null, sdoc, returnFields, i );
> }
>
> }
> if (transformer != null) {
> transformer.setContext(null);
> }
> if(cachMode) {
> for (int i = 0; i < sz; i++) {
> writeSolrDocument(null, cachedDocs[i], returnFields, i);
> }
> }
> writeEndDocumentList();
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