ARROW-8751: [Rust] support empty parquet file in arrow array reader #7140
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nevi-me
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May 14, 2020
sunchao
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Aug 20, 2020
When I was reading a parquet file into `RecordBatches` using `ParquetFileArrowReader` that had row groups that were 100,000 rows in length with a batch size of 60,000, after reading 300,000 rows successfully, I started seeing this error
```
ParquetError("Parquet error: Not all children array length are the same!")
```
Upon investigation, I found that when reading with `ParquetFileArrowReader`, if the parquet input file has multiple row groups, and if a batch happens to end at the end of a row group for Int or Float, no subsequent row groups are read
Visually:
```
+-----+
| RG1 |
| |
+-----+ <-- If a batch ends exactly at the end of this row group (page), RG2 is never read
+-----+
| RG2 |
| |
+-----+
```
I traced the issue down to a bug in `PrimitiveArrayReader` where it mistakenly interprets reading `0` rows from a page reader as being at the end of the column.
This bug appears *not* to be present in the initial implementation #5378 -- FYI @andygrove and @liurenjie1024 (the test harness in this file is awesome, btw), but was introduced in #7140. I will do some more investigating to ensure the test case described in that ticket is handled
Closes #8007 from alamb/alamb/ARROW-9790-record-batch-boundaries
Authored-by: alamb <[email protected]>
Signed-off-by: Chao Sun <[email protected]>
alamb
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to apache/arrow-rs
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Apr 20, 2021
When I was reading a parquet file into `RecordBatches` using `ParquetFileArrowReader` that had row groups that were 100,000 rows in length with a batch size of 60,000, after reading 300,000 rows successfully, I started seeing this error
```
ParquetError("Parquet error: Not all children array length are the same!")
```
Upon investigation, I found that when reading with `ParquetFileArrowReader`, if the parquet input file has multiple row groups, and if a batch happens to end at the end of a row group for Int or Float, no subsequent row groups are read
Visually:
```
+-----+
| RG1 |
| |
+-----+ <-- If a batch ends exactly at the end of this row group (page), RG2 is never read
+-----+
| RG2 |
| |
+-----+
```
I traced the issue down to a bug in `PrimitiveArrayReader` where it mistakenly interprets reading `0` rows from a page reader as being at the end of the column.
This bug appears *not* to be present in the initial implementation #5378 -- FYI @andygrove and @liurenjie1024 (the test harness in this file is awesome, btw), but was introduced in apache/arrow#7140. I will do some more investigating to ensure the test case described in that ticket is handled
Closes #8007 from alamb/alamb/ARROW-9790-record-batch-boundaries
Authored-by: alamb <[email protected]>
Signed-off-by: Chao Sun <[email protected]>
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Sometimes spark will write out parquet files with zero row groups, which will result in error if read using ParquetFileArrowReader.
It would be more convenient if ParquetFileArrowReader can support this edge-case out of the box.