[OAK-2852] Query engine: if counter index is not available, cost of traversing is too low

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.3.7, 1.4
• Component/s: query
• Labels: performance
• Epic Link: Query performance improvements
• Assignee: Thomas Mueller
• Reporter: Thomas Mueller
• Created: 07/May/15 14:42
• Updated: 03/Mar/16 10:16
• Resolved: 23/Sep/15 13:22

Description

If the traversing index is not available (by removing or renaming the node /oak:index/counter), the cost of traversing is relatively low. This can cause traversals, even thought using a property index (or another index) would be better.

By the way, disabling the counter index (setting the type to a 'disabled') alone does still use the estimation in the counter index. This may or may not be a good thing.

Example costs:

/jcr:root/content//element(*, cq:Page)[@test='withCounter']
cost for aggregate lucene is Infinity
cost for lucene-property is Infinity
cost for reference is Infinity
cost for ordered is Infinity
cost for nodeType is 138.0
cost for property is Infinity
cost for traverse is 27100.0

/jcr:root/content//element(*, cq:Page)[@test='withoutCounter2']
cost for aggregate lucene is Infinity
cost for lucene-property is Infinity
cost for reference is Infinity
cost for ordered is Infinity
cost for nodeType is 1504.0
cost for property is Infinity
cost for traverse is 2000.0

Issue Links

• is duplicated by: OAK-2839 Without "counter" index, some queries use traversal instead of an index
• is related to: OAK-1907 Better cost estimates for traversal, property, and ordered indexes