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https://issues.apache.org/jira/browse/SOLR-5855?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Smiley updated SOLR-5855:
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Attachment: SOLR-5855_with_FVH_support.patch
This is an improvement over my past 30min ago. This one uses a TermVector
caching IndexReader wrapper for both the FVH and standard highlighter code
paths, which is more congruent. But it also means that the term vector fetch
won't even happen if there are no text stored data to highlight, since both
highlighters try to get the stored text first.
I also tweaked some internal methods to be a little more consistent. Tests
pass.
> re-use document term-vector Fields instance across fields in the
> DefaultSolrHighlighter
> ---------------------------------------------------------------------------------------
>
> Key: SOLR-5855
> URL: https://issues.apache.org/jira/browse/SOLR-5855
> Project: Solr
> Issue Type: Improvement
> Components: highlighter
> Affects Versions: Trunk
> Reporter: Daniel Debray
> Assignee: David Smiley
> Fix For: 5.2
>
> Attachments: SOLR-5855-without-cache.patch,
> SOLR-5855_with_FVH_support.patch, SOLR-5855_with_FVH_support.patch,
> highlight.patch
>
>
> Hi folks,
> while investigating possible performance bottlenecks in the highlight
> component i discovered two places where we can save some cpu cylces.
> Both are in the class org.apache.solr.highlight.DefaultSolrHighlighter
> First in method doHighlighting (lines 411-417):
> In the loop we try to highlight every field that has been resolved from the
> params on each document. Ok, but why not skip those fields that are not
> present on the current document?
> So i changed the code from:
> for (String fieldName : fieldNames) {
> fieldName = fieldName.trim();
> if( useFastVectorHighlighter( params, schema, fieldName ) )
> doHighlightingByFastVectorHighlighter( fvh, fieldQuery, req,
> docSummaries, docId, doc, fieldName );
> else
> doHighlightingByHighlighter( query, req, docSummaries, docId, doc,
> fieldName );
> }
> to:
> for (String fieldName : fieldNames) {
> fieldName = fieldName.trim();
> if (doc.get(fieldName) != null) {
> if( useFastVectorHighlighter( params, schema, fieldName ) )
> doHighlightingByFastVectorHighlighter( fvh, fieldQuery, req,
> docSummaries, docId, doc, fieldName );
> else
> doHighlightingByHighlighter( query, req, docSummaries, docId, doc,
> fieldName );
> }
> }
> The second place is where we try to retrieve the TokenStream from the
> document for a specific field.
> line 472:
> TokenStream tvStream =
> TokenSources.getTokenStreamWithOffsets(searcher.getIndexReader(), docId,
> fieldName);
> where..
> public static TokenStream getTokenStreamWithOffsets(IndexReader reader, int
> docId, String field) throws IOException {
> Fields vectors = reader.getTermVectors(docId);
> if (vectors == null) {
> return null;
> }
> Terms vector = vectors.terms(field);
> if (vector == null) {
> return null;
> }
> if (!vector.hasPositions() || !vector.hasOffsets()) {
> return null;
> }
> return getTokenStream(vector);
> }
> keep in mind that we currently hit the IndexReader n times where n =
> requested rows(documents) * requested amount of highlight fields.
> in my usecase reader.getTermVectors(docId) takes around 150.000~250.000ns on
> a warm solr and 1.100.000ns on a cold solr.
> If we store the returning Fields vectors in a cache, this lookups only take
> 25000ns.
> I would suggest something like the following code in the
> doHighlightingByHighlighter method in the DefaultSolrHighlighter class (line
> 472):
> Fields vectors = null;
> SolrCache termVectorCache = searcher.getCache("termVectorCache");
> if (termVectorCache != null) {
> vectors = (Fields) termVectorCache.get(Integer.valueOf(docId));
> if (vectors == null) {
> vectors = searcher.getIndexReader().getTermVectors(docId);
> if (vectors != null) termVectorCache.put(Integer.valueOf(docId), vectors);
> }
> } else {
> vectors = searcher.getIndexReader().getTermVectors(docId);
> }
> TokenStream tvStream = TokenSources.getTokenStreamWithOffsets(vectors,
> fieldName);
> and TokenSources class:
> public static TokenStream getTokenStreamWithOffsets(Fields vectors, String
> field) throws IOException {
> if (vectors == null) {
> return null;
> }
> Terms vector = vectors.terms(field);
> if (vector == null) {
> return null;
> }
> if (!vector.hasPositions() || !vector.hasOffsets()) {
> return null;
> }
> return getTokenStream(vector);
> }
> 4000ms on 1000 docs without cache
> 639ms on 1000 docs with cache
> 102ms on 30 docs without cache
> 22ms on 30 docs with cache
> on an index with 190.000 docs with a numFound of 32000 and 80 different
> highlight fields.
> I think querys with only one field to highlight on a document does not
> benefit that much from a cache like this, thats why i think an optional cache
> would be the best solution there.
> As i saw the FastVectorHighlighter uses more or less the same approach and
> could also benefit from this cache.
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