devanbenz commented on PR #27126:
URL: https://github.com/apache/datafusion/pull/27126#issuecomment-6689718905
I am unable to run benchmarks, but, could we get them ran against tpcds with
and without pushdown and tpch10 without pushdown too in the PR?
I ran through some more benchmarks locally and noticed some regressions:
| Benchmark | `main` (70f2ed01b) | PR (a2c3adb04) | Change | Slower / faster
(>5%) |
|---|---:|---:|---:|---:|
| TPC-DS SF1 | 7,857 ms | 8,663 ms | +10.3% | 49 / 12 |
| TPC-DS SF1, `--simulate-latency` | 54,417 ms | 75,615 ms | +39.0% | 73 /
13 |
| TPC-H SF10 | 8,268 ms | 8,384 ms | +1.4% | 1 / 1 |
| Synthetic: 3 CollectLeft aggregate builds, `target_partitions=4` | 573 ms
| 647 ms | +12.9% | n/a |
| Synthetic: same, `target_partitions=20` | 246 ms | 263 ms | +6.9% | n/a |
| TPC-DS query | `main` | PR | Change | `main` (latency) | PR (latency) |
Change (latency) |
|---|---:|---:|---:|---:|---:|---:|
| q88 | 50.2 ms | 158.4 ms | 3.16x | 367 ms | 3214 ms | 8.76x |
| q28 | 57.7 ms | 157.4 ms | 2.73x | 338 ms | 1045 ms | 3.09x |
| q46 | 9.7 ms | 12.6 ms | 1.29x | 123 ms | 347 ms | 2.81x |
| q89 | 30.4 ms | 32.2 ms | 1.06x | 221 ms | 480 ms | 2.17x |
| q73 | 9.4 ms | 8.8 ms | 0.93x | 59 ms | 127 ms | 2.17x |
| q38 | 50.6 ms | 58.9 ms | 1.16x | 423 ms | 907 ms | 2.14x |
| q81 | 24.1 ms | 33.5 ms | 1.39x | 318 ms | 672 ms | 2.12x |
| q84 | 24.1 ms | 30.8 ms | 1.28x | 226 ms | 438 ms | 1.94x |
| q19 | 35.3 ms | 35.6 ms | 1.01x | 296 ms | 569 ms | 1.92x |
| q74 | 139.9 ms | 157.5 ms | 1.13x | 856 ms | 1628 ms | 1.90x |
I think this change makes it so the build sides that used to run in parallel
run sequentially now? Very much restricting parallelism. It helps when there is
a dynamic filter to prune data but for anything else it limits parallelism.
Something akin to this:
```
main (eager): all build sides start at execute()
build A ████████
build B ██████
build C ███████
probe ████
└─ total ≈ longest build + probe
PR (lazy): each build starts only when its join is polled
build A ████████
build B ██████
build C ███████
probe ████
└─
```
(Thanks claude for taking my word vomit and turning it in to a nice little
diagram :laughing:)
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