PfkD-extended improvement: Optimize performance of pfkd-v2

[dbdness]

• With the extension of pfkd-extended-id.sql (introduction of subqueries that output existing PK columns), the runtime performance has gotten significantly worse

• The query should be optimized

• Fix the duplicate subqueries that output the same results; find ways to run only once (temporary table, variable or alias'ed subquery etc.)

• Lose the DISTINCT keywords and use appropriate GROUP BYs instead

• Compare the new runtime with the old one

• Consider creating issues for optimizing our other major queries as well

[dbdness]

Commit 9383b72 forbedrer performance med over 10 sekunder, blot ved at fjerne overflødige JOINs i pkd-subqueries, men jeg tænker der stadig er flere forbedringer at hente.

[dbdness]

Commit 48c5e9d forbedrer performance med yderligere 1 sekund, også ved at fjerne flere overflødige JOINs, hvilket bringer pfkd-v2 query builder execution ned på ~0.244 sekunder.