[TYPO3-performance] Re: 4.7 to 6.2 slow down

[Philipp Wrann]

Of course using the ORM is slower than plain SQL

ORMs do mapping, the map all results in objects, if objects have other entities as properties that are not lazy additional queries are made
ORMs do select * and therfore cant do indexonly queries

But why do you need to load 1000 Entities at once?
When setting up the model proper and doing regular stuff (eg load 10-20 entities and implement some kind of paging) TYPO3 6.2 is quiet fast.

Important:
Add @lazy to all properties that are not simple (1:1, 1:N, M:N Relations) 
Set up APC Caching for all possible caches
Dont render the same link multiple times, use alias viewhelper to assign a generated URI and use it multiple times
Dont render many different image sizes, try to only use 2-3 variants
Avoid uncached elements, this is where TYPO3 6x compared to TYPO3 4x sucks.