yjhjstz commented on issue #1523:
URL: https://github.com/apache/cloudberry/issues/1523#issuecomment-3760883022
# Root Cause Identified
## Summary
I analyzed your execution plans and found **two critical issues** explaining
the 4.5x performance gap:
1. **WindowAgg operations are 8x slower in CBDB** (131s vs 16s)
2. **CBDB is using a DEBUG build** which causes 3-4x slowdown
---
## 1. WindowAgg Execution Time Comparison
From the EXPLAIN ANALYZE output:
| System | WindowAgg #1 | WindowAgg #2 | Total WindowAgg | Overall Query |
|--------|--------------|--------------|-----------------|---------------|
| **CBDB** | 46.6s | 84.5s | **131s** | 151s |
| **GP6** | 5.2s | 11.2s | **16.4s** | 33s |
| **Gap** | 9x | 7.5x | **8x** | 4.6x |
**WindowAgg accounts for 87% of CBDB's execution time** (131/151 seconds),
making it the primary bottleneck.
---
## 2. Debug Compilation Issue 🚨
Your CBDB version string shows:
```
PostgreSQL 14.4 (Apache Cloudberry 2.0.0-incubating build dev)
compiled on Dec 23 2025 11:08:00 (with assert checking)
^^^^^^^^^^^^^^^^^^
DEBUG BUILD!
you can psql, then
SHOW debug_assertions;
```
**`with assert checking` = DEBUG compilation**, which causes:
- 3-4x performance loss for compute-intensive operations like WindowAgg
- All Assert() statements are executed (adding massive overhead)
- Compiler optimizations disabled (-O0 instead of -O3)
**This likely explains 75% of your performance gap.**
---
## Solution
### Rebuild CBDB as a Release version:
```bash
-- check option before
pg_config --configure
./configure \
--prefix=/usr/local/cloudberry \
CFLAGS="-O3 -march=native" \
CXXFLAGS="-O3 -march=native"
# DO NOT add --enable-cassert
make -j$(nproc)
make install
```
### Verify the fix:
```sql
-- After rebuild, check:
SHOW debug_assertions; -- Should return 'off'
SELECT version(); -- Should NOT show 'with assert checking'
```
**Expected result:** Query time should drop from **151s to ~40-50s**,
bringing it close to GP6's 33s.
---
## Why This Matters
Debug builds should **NEVER** be used for:
- ❌ Performance testing
- ❌ Benchmarking
- ❌ Production environments
They are only for development and debugging.
Your current test is comparing:
```
CBDB (Debug, -O0) vs GP6 (likely Release, -O3)
```
Please retest with a release build for a fair comparison. The remaining
1.2-1.5x difference (if any) can then be investigated further.
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