Truncate Min/Max values in the Column Index #4389
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| Original file line number | Diff line number | Diff line change |
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@@ -656,8 +656,8 @@ impl<'a, E: ColumnValueEncoder> GenericColumnWriter<'a, E> { | |
| if null_page && self.column_index_builder.valid() { | ||
| self.column_index_builder.append( | ||
| null_page, | ||
| vec![0; 1], | ||
| vec![0; 1], | ||
| self.page_metrics.num_page_nulls as i64, | ||
| ); | ||
| } else if self.column_index_builder.valid() { | ||
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@@ -670,8 +670,8 @@ impl<'a, E: ColumnValueEncoder> GenericColumnWriter<'a, E> { | |
| Some(stat) => { | ||
| self.column_index_builder.append( | ||
| null_page, | ||
| self.truncate_min_value(stat.min_bytes()), | ||
| self.truncate_max_value(stat.max_bytes()), | ||
| self.page_metrics.num_page_nulls as i64, | ||
| ); | ||
| } | ||
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@@ -683,6 +683,35 @@ impl<'a, E: ColumnValueEncoder> GenericColumnWriter<'a, E> { | |
| .append_row_count(self.page_metrics.num_buffered_rows as i64); | ||
| } | ||
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| fn truncate_min_value(&self, data: &[u8]) -> Vec<u8> { | ||
| let max_effective_len = | ||
| self.props.minmax_value_truncate_len().unwrap_or(data.len()); | ||
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| match std::str::from_utf8(data) { | ||
| Ok(str_data) => truncate_utf8(str_data, max_effective_len), | ||
| Err(_) => truncate_binary(data, max_effective_len), | ||
| } | ||
| } | ||
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| fn truncate_max_value(&self, data: &[u8]) -> Vec<u8> { | ||
| // Even if the user disables value truncation, we want to make sure to increase the max value so the user doesn't miss it. | ||
| let max_effective_len = | ||
| self.props.minmax_value_truncate_len().unwrap_or(data.len()); | ||
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| match std::str::from_utf8(data) { | ||
| Ok(str_data) => { | ||
| let mut v = truncate_utf8(str_data, max_effective_len); | ||
| increment_utf8(&mut v); | ||
| v | ||
| } | ||
| Err(_) => { | ||
| let mut v = truncate_binary(data, max_effective_len); | ||
| increment(&mut v); | ||
| v | ||
| } | ||
| } | ||
| } | ||
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| /// Adds data page. | ||
| /// Data page is either buffered in case of dictionary encoding or written directly. | ||
| fn add_data_page(&mut self) -> Result<()> { | ||
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@@ -1152,6 +1181,56 @@ fn compare_greater_byte_array_decimals(a: &[u8], b: &[u8]) -> bool { | |
| (a[1..]) > (b[1..]) | ||
| } | ||
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| /// Truncate a UTF8 slice to the longest prefix that is still a valid UTF8 string, while being less than `max_len` bytes. | ||
| fn truncate_utf8(data: &str, max_len: usize) -> Vec<u8> { | ||
| let mut max_possible_len = usize::min(data.len(), max_len); | ||
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| if data.is_char_boundary(max_possible_len) { | ||
| return data.as_bytes()[0..max_possible_len].to_vec(); | ||
| } | ||
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| // UTF8 characters can only be up to 4 bytes long, so this loop has will only run up to 3 times before returning. | ||
| loop { | ||
| max_possible_len -= 1; | ||
| if data.is_char_boundary(max_possible_len) { | ||
| return data.as_bytes()[0..max_possible_len].to_vec(); | ||
| } | ||
| } | ||
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| } | ||
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| /// Truncate a binary slice to make sure its length is less than `max_len` | ||
| fn truncate_binary(data: &[u8], max_len: usize) -> Vec<u8> { | ||
| data[0..usize::min(data.len(), max_len)].to_vec() | ||
| } | ||
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| /// Try and increment the bytes from right to left. | ||
| fn increment(data: &mut [u8]) { | ||
| for byte in data.iter_mut().rev() { | ||
| if *byte == u8::MAX { | ||
|
There was a problem hiding this comment. What if the sequence is There was a problem hiding this comment. I think this is still outstanding, right? Is the solution to just return There was a problem hiding this comment. Adopted their (parquet-mr) general structure with functions returning None when they can't truncate/increment. |
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| continue; | ||
| } else { | ||
| *byte += 1; | ||
| break; | ||
| } | ||
| } | ||
| } | ||
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| /// Try and increment the the string's bytes from right to left, returning when the result is a valid UTF8 string. | ||
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| fn increment_utf8(data: &mut Vec<u8>) { | ||
| for idx in (0..data.len()).rev() { | ||
| let byte = &mut data[idx]; | ||
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| if *byte == u8::MAX { | ||
| continue; | ||
| } else { | ||
| *byte += 1; | ||
| } | ||
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| if std::str::from_utf8(data).is_ok() { | ||
| break; | ||
| } | ||
| } | ||
| } | ||
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| #[cfg(test)] | ||
| mod tests { | ||
| use crate::format::BoundaryOrder; | ||
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@@ -2198,10 +2277,11 @@ mod tests { | |
| // first page is [1,2,3,4] | ||
| // second page is [-5,2,4,8] | ||
| assert_eq!(stats.min_bytes(), column_index.min_values[1].as_slice()); | ||
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| // We expect the max value to be incremented | ||
| let mut stats_max_bytes = stats.max_bytes().to_vec(); | ||
| increment(&mut stats_max_bytes); | ||
| assert_eq!(&stats_max_bytes, column_index.max_values.get(1).unwrap()); | ||
| } else { | ||
| panic!("expecting Statistics::Int32"); | ||
| } | ||
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@@ -2220,12 +2300,182 @@ mod tests { | |
| ); | ||
| } | ||
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| /// Verify min/max value truncation in the column index works as expected | ||
| #[test] | ||
| fn test_column_offset_index_metadata_truncating() { | ||
| // write data | ||
| // and check the offset index and column index | ||
| let page_writer = get_test_page_writer(); | ||
| let props = Default::default(); | ||
| let mut writer = | ||
| get_test_column_writer::<FixedLenByteArrayType>(page_writer, 0, 0, props); | ||
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| let mut data = vec![FixedLenByteArray::default(); 3]; | ||
| // This is the expected min value | ||
| data[0].set_data(ByteBufferPtr::new(vec![0_u8; 200])); | ||
| // This is the expected max value | ||
| data[1].set_data(ByteBufferPtr::new( | ||
| String::from("Zorro the masked hero").into_bytes(), | ||
| )); | ||
| data[2].set_data(ByteBufferPtr::new(Vec::from_iter(0_u8..129))); | ||
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| writer.write_batch(&data, None, None).unwrap(); | ||
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| writer.flush_data_pages().unwrap(); | ||
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| let r = writer.close().unwrap(); | ||
| let column_index = r.column_index.unwrap(); | ||
| let offset_index = r.offset_index.unwrap(); | ||
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| assert_eq!(3, r.rows_written); | ||
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| // column index | ||
| assert_eq!(1, column_index.null_pages.len()); | ||
| assert_eq!(1, offset_index.page_locations.len()); | ||
| assert_eq!(BoundaryOrder::UNORDERED, column_index.boundary_order); | ||
| assert!(!column_index.null_pages[0]); | ||
| assert_eq!(0, column_index.null_counts.as_ref().unwrap()[0]); | ||
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| if let Some(stats) = r.metadata.statistics() { | ||
| assert!(stats.has_min_max_set()); | ||
| assert_eq!(stats.null_count(), 0); | ||
| assert_eq!(stats.distinct_count(), None); | ||
| if let Statistics::FixedLenByteArray(stats) = stats { | ||
| let column_index_min_value = column_index.min_values.get(0).unwrap(); | ||
| let column_index_max_value = column_index.max_values.get(0).unwrap(); | ||
|
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| // Column index stats are truncated, while the column chunk's aren't. | ||
| assert_ne!(stats.min_bytes(), column_index_min_value.as_slice()); | ||
| // We expect the max value to be incremented | ||
| let mut stats_max_bytes = stats.max_bytes().to_vec(); | ||
| increment(&mut stats_max_bytes); | ||
| assert_eq!(stats_max_bytes, column_index_max_value.as_slice()); | ||
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| assert_eq!(column_index_min_value.len(), 128); | ||
| assert_eq!(column_index_min_value.as_slice(), &[0_u8; 128]); | ||
| assert_eq!(column_index_max_value.len(), 21); | ||
| } else { | ||
| panic!("expecting Statistics::FixedLenByteArray"); | ||
| } | ||
| } else { | ||
| panic!("metadata missing statistics"); | ||
| } | ||
| } | ||
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| #[test] | ||
| fn test_column_offset_index_metadata_truncating_spec_example() { | ||
| // write data | ||
| // and check the offset index and column index | ||
| let page_writer = get_test_page_writer(); | ||
| let builder = WriterProperties::builder().set_value_truncate_length(Some(1)); | ||
| let props = Arc::new(builder.build()); | ||
| let mut writer = | ||
| get_test_column_writer::<FixedLenByteArrayType>(page_writer, 0, 0, props); | ||
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| let mut data = vec![FixedLenByteArray::default(); 1]; | ||
| // This is the expected min value | ||
| data[0].set_data(ByteBufferPtr::new( | ||
| String::from("Blart Versenwald III").into_bytes(), | ||
| )); | ||
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| writer.write_batch(&data, None, None).unwrap(); | ||
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| writer.flush_data_pages().unwrap(); | ||
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| let r = writer.close().unwrap(); | ||
| let column_index = r.column_index.unwrap(); | ||
| let offset_index = r.offset_index.unwrap(); | ||
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| assert_eq!(1, r.rows_written); | ||
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| // column index | ||
| assert_eq!(1, column_index.null_pages.len()); | ||
| assert_eq!(1, offset_index.page_locations.len()); | ||
| assert_eq!(BoundaryOrder::UNORDERED, column_index.boundary_order); | ||
| assert!(!column_index.null_pages[0]); | ||
| assert_eq!(0, column_index.null_counts.as_ref().unwrap()[0]); | ||
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| if let Some(stats) = r.metadata.statistics() { | ||
| assert!(stats.has_min_max_set()); | ||
| assert_eq!(stats.null_count(), 0); | ||
| assert_eq!(stats.distinct_count(), None); | ||
| if let Statistics::FixedLenByteArray(_stats) = stats { | ||
| let column_index_min_value = column_index.min_values.get(0).unwrap(); | ||
| let column_index_max_value = column_index.max_values.get(0).unwrap(); | ||
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| assert_ne!(column_index_min_value, column_index_max_value); | ||
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| assert_eq!(column_index_min_value.len(), 1); | ||
| assert_eq!(column_index_max_value.len(), 1); | ||
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| // Column index stats are truncated, while the column chunk's aren't. | ||
| assert_eq!("B".as_bytes(), column_index_min_value.as_slice()); | ||
| // In this case, they are equal because the max value is shorter than the default threshold | ||
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| assert_eq!("C".as_bytes(), column_index_max_value.as_slice()); | ||
| } else { | ||
| panic!("expecting Statistics::FixedLenByteArray"); | ||
| } | ||
| } else { | ||
| panic!("metadata missing statistics"); | ||
| } | ||
| } | ||
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| #[test] | ||
| fn test_send() { | ||
| fn test<T: Send>() {} | ||
| test::<ColumnWriterImpl<Int32Type>>(); | ||
| } | ||
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| #[test] | ||
| fn test_increment() { | ||
| let mut v = vec![0, 0, 0]; | ||
| increment(&mut v); | ||
| assert_eq!(&v, &[0, 0, 1]); | ||
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| // Handle overflow | ||
| let mut v = vec![0, 255, 255]; | ||
| increment(&mut v); | ||
| assert_eq!(&v, &[1, 255, 255]); | ||
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| // No-op if all bytes are u8::MAX | ||
| let mut v = vec![255, 255, 255]; | ||
| increment(&mut v); | ||
| assert_eq!(&v, &[255, 255, 255]); | ||
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| } | ||
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| #[test] | ||
| fn test_increment_utf8() { | ||
| // Basic ASCII case | ||
| let mut v = "hello".as_bytes().to_vec(); | ||
| increment_utf8(&mut v); | ||
| assert_eq!(&v, "hellp".as_bytes()); | ||
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| // Utf8 string | ||
| let s = "❤️🧡💛💚💙💜"; | ||
| let mut v = s.as_bytes().to_vec(); | ||
| increment_utf8(&mut v); | ||
| if let Ok(new) = String::from_utf8(v) { | ||
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| assert_ne!(&new, s); | ||
| assert_eq!(new, "❤️🧡💛💚💙💝"); | ||
| } else { | ||
| panic!("Expected incremented UTF8 string to also be valid.") | ||
| } | ||
| } | ||
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| #[test] | ||
| fn test_truncate_utf8() { | ||
| // No-op | ||
| let data = "❤️🧡💛💚💙💜"; | ||
| let r = truncate_utf8(data, data.as_bytes().len()); | ||
| assert_eq!(r.len(), data.as_bytes().len()); | ||
| assert_eq!(&r, data.as_bytes()); | ||
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| // We slice it away from the UTF8 boundary | ||
| let r = truncate_utf8(data, 13); | ||
| assert_eq!(r.len(), 10); | ||
| assert_eq!(&r, "❤️🧡".as_bytes()) | ||
| } | ||
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| /// Performs write-read roundtrip with randomly generated values and levels. | ||
| /// `max_size` is maximum number of values or levels (if `max_def_level` > 0) to write | ||
| /// for a column. | ||
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I think we should only increment if we are truncating, I think it would be a bit surprising for users to write
b"hello"and get backb"hellp". Whereas writing"really long string"and getting back an obviously truncated string is perhaps more understandable"really long su"There was a problem hiding this comment.
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Agreed, it should be handled correctly now