Every AEM developer faced with below exception which means that we are exceeded the limit of nodes for reading:

java.lang.UnsupportedOperationException: The query read or traversed more than 100000 nodes. To avoid affecting other tasks, processing was stopped.
	at org.apache.jackrabbit.oak.query.FilterIterators.checkReadLimit(FilterIterators.java:70)
	at org.apache.jackrabbit.oak.plugins.index.Cursors.checkReadLimit(Cursors.java:67)
	at org.apache.jackrabbit.oak.plugins.index.lucene.LucenePropertyIndex$LucenePathCursor$1.next(LucenePropertyIndex.java:1730)
	at org.apache.jackrabbit.oak.plugins.index.lucene.LucenePropertyIndex$LucenePathCursor$1.next(LucenePropertyIndex.java:1711)
	at com.google.common.collect.Iterators$7.computeNext(Iterators.java:646)
	at com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:143)
	at com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:138)
	at org.apache.jackrabbit.oak.plugins.index.Cursors$PathCursor.hasNext(Cursors.java:216)
	at org.apache.jackrabbit.oak.plugins.index.lucene.LucenePropertyIndex$LucenePathCursor.hasNext(LucenePropertyIndex.java:1751)
	at org.apache.jackrabbit.oak.query.ast.SelectorImpl.next(SelectorImpl.java:432)
	at org.apache.jackrabbit.oak.query.QueryImpl$RowIterator.fetchNext(QueryImpl.java:824)
	at org.apache.jackrabbit.oak.query.QueryImpl$RowIterator.hasNext(QueryImpl.java:851)
	at org.apache.jackrabbit.oak.jcr.query.QueryResultImpl$1.fetch(QueryResultImpl.java:98)

In this situation, we can:

• define the oak index for a query
• try to redesign taxonomy of a repository or structure if it might be improved
• update oak indexes to cover the query
• use oak:Unstructured instead of nt:unstructured and sling:Folder instead of sling:OrderedFolder in a case where an order is not required
• etc.

During the development, if we want to skip this error for a while we can increase LimitReads and LimitInMemory parameters for OAK Query Engine:

1. navigate to  QueryEngineSettings
2.  increase selected parameters:
   
3. this is for development stage only, please, do not push this on production

Links to resources for help:

1. Oak Index Definition Generator

2. Best Practices for Queries and Indexing