csv: Add option to specify custom null values #4795
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Have you run the benchmarks for this change? |
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I'll try to make some improvements here. |
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You may need to help LLVM by pulling the conditional out of the loop for it |
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Updated changes: |
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I also ran the benchmarks and got similar results, I'm honestly somewhat surprised but I guess string parsing inherently has a lot of conditionals. Edit: Actually running this with slightly more realistic benchmarks, that use smaller integers, this shows a 10% performance regression still... I'll get a PR up with these so that you can take a look Edit Edit: Benchmarks in #4803 |
tustvold
reviewed
Sep 9, 2023
arrow-csv/src/reader/mod.rs
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| @@ -241,6 +243,11 @@ impl Format { | |||
| self | |||
| } | |||
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| pub fn with_nulls(mut self, nulls: HashSet<String>) -> Self { | |||
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I wonder if a Regex might be a more flexible interface, and more consistent with how we express things for schema inference. It might also perform better
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Makes sense! I will try this with regex.
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Regex performs worse in case there's a custom regex provided. I can push a commit with the regex change. The benchmarks should be similar. |
vrongmeal
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The latest changes seem to do quite well: |
tustvold
reviewed
Sep 11, 2023
| @@ -241,6 +242,11 @@ impl Format { | |||
| self | |||
| } | |||
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| pub fn with_null_regex(mut self, null_regex: Regex) -> Self { | |||
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Perhaps some doc comments?
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Yup, I will add doc comments.
arrow-csv/src/reader/mod.rs
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| @@ -319,6 +325,7 @@ impl Format { | |||
| if let Some(t) = self.terminator { | |||
| builder.terminator(csv::Terminator::Any(t)); | |||
| } | |||
| // TODO: Null regex | |||
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My mistake, I thought it was building the arrow CSV reader.
arrow-csv/src/reader/mod.rs
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| @@ -336,6 +343,7 @@ impl Format { | |||
| if let Some(t) = self.terminator { | |||
| builder.terminator(csv_core::Terminator::Any(t)); | |||
| } | |||
| // TODO: Null regex | |||
arrow-csv/src/reader/mod.rs
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| ) -> Result<ArrayRef, ArrowError> { | ||
| let mut decimal_builder = PrimitiveBuilder::<T>::with_capacity(rows.len()); | ||
| for row in rows.iter() { | ||
| let s = row.get(col_idx); | ||
| if s.is_empty() { | ||
| if s.is_empty() || null_regex.is_some_and(|r| r.is_match(s)) { |
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If a null regex is provided should we also treat empty strings as nulls?
Edit: BTW TIL about is_some_and, very nice 👌
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Let's avoid checking is_empty in that case. Users can configure the regex to include it as well.
tustvold
reviewed
Sep 11, 2023
arrow-csv/src/reader/mod.rs
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| null_regex: Option<Regex>, | ||
| } | ||
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| impl Debug for Decoder { |
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I'll undo this. It was when the struct had is_null closure.
Can specify custom strings as `NULL` values for CSVs as a regular expression. This allows reading a CSV files which have placeholders for NULL values instead of empty strings. Fixes apache#4794 Signed-off-by: Vaibhav <[email protected]>
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Cleaned up the PR. I made some minor refactors. Here we are with the final benchmarks (not much different from the previous ones): |
tustvold
approved these changes
Sep 13, 2023
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I took the liberty of applying the docs changes so I can get this in |
Thank you so much! |
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Can specify custom strings as
NULLvalues for CSVs. This allows reading a CSV files which have placeholders for NULL values instead of empty strings.Which issue does this PR close?
Closes #4794
Rationale for this change
What changes are included in this PR?
Are there any user-facing changes?