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Implementation details have been anonymized to protect intellectual property. The methodology, metrics, and results are real. For the full technical breakdown, reach out at tomas@omnimetrix.io.
Loop 04: CTE Pipeline Reduction
BEFORE
AFTER
Loop 04: CTE Pipeline Reduction
What changed
The query pipeline used 11 chained common table expressions (CTEs). Two adjacent CTEs -- each applying a formatting transformation -- were merged into a single CTE using nested conditional expressions, reducing the pipeline to 10 stages.
Why we expected it to work
Each CTE stage potentially triggers intermediate result materialization in the database. Eliminating one stage should remove one materialization pass over ~5,000-10,000 rows, saving an estimated 10-40ms per query.
Results
| Metric | Before | After | Delta |
|---|---|---|---|
| Mean response time | 1061ms | 1047ms | -1.3% |
| Min response time | 1019ms | 1013ms | -0.6% |
| Max response time | 1096ms | 1097ms | +0.1% |
Why it didn't work
The database query optimizer already inlines single-reference CTEs automatically. The merged CTE was never materialized as an intermediate result set in the first place, so removing it had no effect on the execution plan. The 14ms delta falls well within the 80ms measurement variance. Query-structure optimizations have reached diminishing returns after Loops 01 and 02.
Cumulative impact
Original: 1,829ms → After Loop 04: 852ms (53.4% total reduction, unchanged)