Enable cache of XML fragment for node, way and relation

[yuiseki]

What

This pull request changes just three files on this rails application

• app/views/api/nodes/_node.xml.builder
• app/views/api/ways/_way.xml.builder
• app/views/api/relations/_relation.xml.builder

Why

• Currently, this rails app does not cache fragment of XML
• This should slow down the XML building
• Whether the caching mechanism is memory or files, it should be faster than executing SQL queries and building XML
• These files appear to have been last edited four years ago, but modern Rails' caching of XML fragments has progressed

How

• Change the Rails Model instance handled by *.xml.builder to be passed to cache method of the Rails view
• If there are no changes to the records in the Rails Model, the SQL query execution and XML construction will be skipped and the cache will be used
• If the Rails Model record changes, the cache is destroyed and the XML is updated appropriately

My opinion

• This change should be carefully considered as it will likely affect the behavior of the Production environment
• Still, I believe it should have a big positive impact on performance
• Please consider it and let me know what you think!

[tomhughes]

Well this will have no effect on our production environment because we don't serve those endpoints from the rails code - they are served by cgimap.

If we were using it in production then the problem would be the impact on our cache and the fact that unless we provisioned a lot more cache it would probably cause more important things (like user sessions) to be evicted.

[mmd-osm]

OpenHistoricalMap uses the rails code, and I’m not aware of anyone reporting issues with iD. OP also didn’t present any runtime comparison.

I would close this issue.