Trejkaz created LUCENE-6503:
-------------------------------
Summary: QueryWrapperFilter discards the IndexReaderContext when
delegating to the wrapped query
Key: LUCENE-6503
URL: https://issues.apache.org/jira/browse/LUCENE-6503
Project: Lucene - Core
Issue Type: Bug
Components: core/search
Affects Versions: 4.10.4
Reporter: Trejkaz
Suppose I have a working {{Filter}} which depends on the context within the
composite reader, e.g., one which has a global BitSet of the docs which match
but needs to know the docBase and maxDoc for the individual reader in order to
return the correct set to the caller.
This is wrapped into a {{ConstantScoreQuery}} in order to become part of a
{{BooleanQuery}} tree.
At some other layer, the entire query tree is wrapped back into a
{{QueryWrapperFilter}} by some other code which wants to cache the results as a
Filter.
QueryWrapperFilter has code like this:
{code}
@Override
public DocIdSet getDocIdSet(final AtomicReaderContext context, final Bits
acceptDocs) throws IOException {
// get a private context that is used to rewrite, createWeight and score
eventually
final AtomicReaderContext privateContext = context.reader().getContext();
final Weight weight = new
IndexSearcher(privateContext).createNormalizedWeight(query);
return new DocIdSet() {
@Override
public DocIdSetIterator iterator() throws IOException {
return weight.scorer(privateContext, acceptDocs);
}
@Override
public boolean isCacheable() { return false; }
};
}
{code}
The call to {{reader().getContext()}} returns an {{AtomicReaderContext}} whose
parent is not correctly set.
This is then passed to {{Weight#scorer}} which eventually arrives at
{{ConstantScoreQuery#scorer}}, which calls {{Filter#getDocIdSet}}.
So our innermost {{Filter}} receives an {{AtomicReaderContext}} whose top-level
{{IndexReader}} is not the actual top-level reader. This was detected in our
code because we use a special subclass of DirectoryReader for our top-level
reader and thus the filter failed. (Had it not failed, it would have silently
returned the wrong results.)
The fix I have applied locally is to change the call to:
{code}
return weight.scorer(context, acceptDocs);
{code}
This does appear to be working, but I'm not really sure if it's OK to build the
IndexSearcher using one context while passing another context to the scorer.
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