[OAK-3071] Add a compound index for _modified + _id

• Type: Improvement
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 1.3.15, 1.4
• Component/s: mongomk
• Labels: performance resilience
• Epic Link: Improve DocumentMK performance
• Assignee: Marcel Reutegger
• Reporter: Chetan Mehrotra
• Created: 02/Jul/15 18:08
• Updated: 02/Mar/16 15:22
• Resolved: 02/Feb/16 14:24

Description

As explained in OAK-1966 diff logic makes a call like

db.nodes.find({ _id: { $gt: "3:/content/foo/01/", $lt: "3:/content/foo010" }, _modified: { $gte: 1405085300 } }).sort({_id:1})

For better and deterministic query performance we would need to create a compound index like {_modified:1, _id:1}. This index would ensure that Mongo does not have to perform object scan while evaluating such a query.

Care must be taken that index is only created by default for fresh setup. For existing setup we should expose a JMX operation which can be invoked by system admin to create the required index as per maintenance window

Issue Links

• is blocked by: OAK-3970 Utility methods for MongoDB indexes