apache / apache/datafusion-python
Queries on tables via `register_dataset()` much slower than `register_parquet()`
- 主要語言
- Python
- 星號
- 604
- 分支
- 174
- 平均合併
- 2 天 22 小時
- 30 天內合併 PR
- 5
描述
**Describe the bug**
Queries against tables registered with `register_dataset()` perform around 80x slower than those registered with `register_parquet()`.
**To Reproduce**
```
import datafusion
import pyarrow.dataset as ds
from pathlib import Path
ctx = datafusion.SessionContext()
ctx.register_parquet("mytable", "*.parquet")
ctx.register_dataset("mytable2", ds.dataset(list(Path(".").glob("*.parquet"))))
```
Fast:
```
%time ctx.sql('select file_date, sum("Price" * "Volume") from mytable group by file_date order by file_date').to_arrow_table()
CPU times: user 2min 41s, sys: 3.35 s, total: 2min 45s
Wall time: 2.49 s
```
Slow:
```
%time ctx.sql('select file_date, sum("Price" * "Volume") from mytable2 group by file_date order by file_date').to_arrow_table()
CPU times: user 10min 51s, sys: 5min 40s, total: 16min 31s
Wall time: 3min 18s
```
**Expected behavior**
I'd expect these to be similar performance.
**Additional context**
The reason I'm using `ds.dataset` is because the actual files I'm interesting in accessing are not conveniently globbable (they're across multiple directories). So ideally I'd be able to provide a list of files to `ctx.register_parquet()` instead of a simple glob.
貢獻指南
這個儲存庫沒有索引到貢獻指南
研究方向
首先執行重現,使用分組查詢比較 ctx.register_parquet() 和 ctx.register_dataset(),然後追蹤 Python bindings 中的兩個註冊入口。完成標準是相同的 parquet 檔案具有可比較的查詢效能,並且 register_parquet() 可以依要求接受檔案清單。
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評估
- 技術堆疊
- python
- 領域
- data-engineering, performance
- Issue 類型
- 缺陷
- 難度
- 4/5
- 預估耗時
- 3-5 天
- 活躍度
- 停滯
- 描述清晰度
- 基本清楚
- 新手友好度
- 35/100