[OAK-9332] Document best practices and anti-patterns in repository tree traversal

• Type: Documentation
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.40.0
• Component/s: doc
• Assignee: Miroslav Smiljanic
• Reporter: Miroslav Smiljanic
• Created: 21/Jan/21 11:57
• Updated: 03/Jun/21 14:53
• Resolved: 27/May/21 08:54

Description

When using JCR API, there is more than one way to perform tree/path traversal:

Node c = session.getNode("/a/b/c");
Node d = null;

//get child node
d = session.getNode("/a/b/c/d");
d = c.getNode("d");

// get parent node
c = d.getParent();
c = session.getNode("/a/b/c");

To traverse a path using Node API with  performs better compared to Session API. 

> java -jar target/oak-benchmarks-*-SNAPSHOT.jar benchmark  GetParentNodeWithNodeAPI  GetParentNodeWithSessionAPI  Oak-Segment-Tar
Apache Jackrabbit Oak 1.37-SNAPSHOT
# GetParentNodeWithNodeAPI         C     min     10%     50%     90%     max     N       mean 
Oak-Segment-Tar                    1       2       2       2       3      5   25891       2
# GetParentNodeWithSessionAP       C     min     10%     50%     90%     max     N       mean 
Oak-Segment-Tar                    1      26      27      29      32     40    2069      29

Example where Session API is used: https://issues.apache.org/jira/browse/SLING-10011

Considering Oak implementation details (tree repository structure, ACL evaluation, ...) the best practice for path traversal should be explicitly documented.