Add bytes scanned metric to ParquetExec#2273
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andygrove merged 1 commit intoapache:masterfrom Apr 21, 2022
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Apr 20, 2022
| fn get_read(&self, start: u64, length: usize) -> ParquetResult<Self::T> { | ||
| self.0 | ||
| if let Some(m) = self.bytes_scanned.as_ref() { | ||
| m.add(length) |
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I'm just curious .. the length here is the number of bytes requested and could potentially be different from the actual number of bytes read?
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I don't think this interface actually specifies so it would really be up to the specific ObjectStore implementation. I know that that is the way the LocalFileSystem works and I believe that is the way the AWS S3 API works with file ranges.
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Apr 20, 2022
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Which issue does this PR close?
Closes #.
Rationale for this change
Tracking total number of bytes read from storage is an important metric for query execution (especially for use cases where data is read from object storage or NAS rather than a local SSD). It's especially important for Parquet data sources where we have many levers we can pull to reduce the amount of data read.
What changes are included in this PR?
Add a
bytes_scannedcounter toParquetFileMetricsand track total number of bytes read throughChunkObjectReader. This should be quite cheap since we pass the number of bytes to read as an argument.Are there any user-facing changes?
ParquetExecwill have abytes_scannedmetric.No