[SLING-4596] Performance: Consider optimizing JcrItemResource#getParent and getChild

• Type: Improvement
• Status: Resolved
• Priority: Critical
• Resolution: Won't Fix
• Affects Version/s: JCR Resource 2.5.0
• Component/s: JCR, ResourceResolver
• Labels: performance
• Assignee: Unassigned
• Reporter: Joel Richard
• Created: 09/Apr/15 13:50
• Updated: 21/Aug/15 07:55
• Resolved: 21/Aug/15 07:55

Description

I have noticed that on some "resource intensive" pages up to 24% of the rendering time is spent in AbstractResource.getParent. One of the main reasons for this is because the ParentHidingHandler traverses for each resource to the root (see SLING-4568).

getParent is not just called often, but is also about 10 times slower than jcrNode.getParent() which has the following reasons:

• itemExists is called unnecessary because JcrResourceProvider#createResource does not know that the path belongs to a parent of a node which has already been read. See also SLING-4585.
• jcrSession.getItem (which is used to read parents in JcrResourceProvider#createResource) is about 3.5 times slower than jcrNode.getParent in Oak.
• Some other overhead which cannot be avoided entirely.

The situation could be improved with a getParent implementation which is specific to JcrNodeResource and uses getNode().getParent() directly to create a new JcrNodeResource. I have implemented such a method (see attached experimental patch) and it reduces the time for getParent from 24% to 5% on my test page.

As discussed on the mailing list this is not a good solution because the parent resource could be backed by another provider. An alternative approach would be to create a new resource provider interface which accepts the base resource (which is passed to resourceResolver.getResource), retrieves the node form it and uses it for a direct getParent/getNode call (see the linked mail for more information).

Issue Links

• is related to: SLING-4611 Performance: Consider optimizing MergedResource#getParent and getChild
• is superceded by: SLING-4750 New Resource Provider API
• relates to: SLING-4568 Performance: MergingResourceProvider.ParentHidingHandler adds about 30pp rendering overhead
• relates to: SLING-4585 Performance: Use JackrabbitSession#getItemOrNull to speed up JcrResourceProvider#createResource