feat: support 'hive partitioning' aware readers (pola-rs#11284)

Cargo.toml

@@ -58,6 +58,7 @@ streaming-iterator = "0.1.9"
 itoa = "1.0.6"
 ryu = "1.0.13"
 lexical-core = "0.8.5"
+percent-encoding = "2.3"
 xxhash-rust = { version = "0.8.6", features = ["xxh3"] }
 polars-core = { version = "0.33.2", path = "crates/polars-core", default-features = false }
 polars-arrow = { version = "0.33.2", path = "crates/polars-arrow", default-features = false }

crates/polars-core/src/frame/mod.rs

@@ -501,7 +501,7 @@ impl DataFrame {
     /// # Ok::<(), PolarsError>(())
     /// ```
     pub fn schema(&self) -> Schema {
-        self.iter().map(|s| s.field().into_owned()).collect()
+        self.columns.as_slice().into()
     }
 
     /// Get a reference to the [`DataFrame`] columns.

crates/polars-core/src/schema.rs

@@ -34,6 +34,12 @@ impl Debug for Schema {
     }
 }
 
+impl From<&[Series]> for Schema {
+    fn from(value: &[Series]) -> Self {
+        value.iter().map(|s| s.field().into_owned()).collect()
+    }
+}
+
 impl<F> FromIterator<F> for Schema
 where
     F: Into<Field>,

crates/polars-io/src/csv/read_impl/mod.rs

@@ -557,23 +557,7 @@ impl<'a> CoreReader<'a> {
 
         // An empty file with a schema should return an empty DataFrame with that schema
         if bytes.is_empty() {
-            // TODO! add DataFrame::new_from_schema
-            let buffers = init_buffers(
-                &projection,
-                0,
-                &self.schema,
-                &self.init_string_size_stats(&str_columns, 0),
-                self.quote_char,
-                self.encoding,
-                self.ignore_errors,
-            )?;
-            let df = DataFrame::new_no_checks(
-                buffers
-                    .into_iter()
-                    .map(|buf| buf.into_series())
-                    .collect::<PolarsResult<_>>()?,
-            );
-            return Ok(df);
+            return Ok(DataFrame::from(self.schema.as_ref()));
         }
 
         // all the buffers returned from the threads

crates/polars-io/src/csv/utils.rs

@@ -3,22 +3,21 @@ use std::borrow::Cow;
 use std::io::Read;
 use std::mem::MaybeUninit;
 
-use once_cell::sync::Lazy;
 use polars_core::datatypes::PlHashSet;
 use polars_core::prelude::*;
 #[cfg(feature = "polars-time")]
 use polars_time::chunkedarray::utf8::infer as date_infer;
 #[cfg(feature = "polars-time")]
 use polars_time::prelude::utf8::Pattern;
-use regex::{Regex, RegexBuilder};
 
 #[cfg(any(feature = "decompress", feature = "decompress-fast"))]
 use crate::csv::parser::next_line_position_naive;
 use crate::csv::parser::{next_line_position, skip_bom, skip_line_ending, SplitLines};
 use crate::csv::splitfields::SplitFields;
 use crate::csv::CsvEncoding;
-use crate::mmap::*;
+use crate::mmap::ReaderBytes;
 use crate::prelude::NullValues;
+use crate::utils::{BOOLEAN_RE, FLOAT_RE, INTEGER_RE};
 
 pub(crate) fn get_file_chunks(
     bytes: &[u8],
@@ -58,19 +57,6 @@ pub(crate) fn get_file_chunks(
     offsets
 }
 
-static FLOAT_RE: Lazy<Regex> = Lazy::new(|| {
-    Regex::new(r"^\s*[-+]?((\d*\.\d+)([eE][-+]?\d+)?|inf|NaN|(\d+)[eE][-+]?\d+|\d+\.)$").unwrap()
-});
-
-static INTEGER_RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"^\s*-?(\d+)$").unwrap());
-
-static BOOLEAN_RE: Lazy<Regex> = Lazy::new(|| {
-    RegexBuilder::new(r"^\s*(true)$|^(false)$")
-        .case_insensitive(true)
-        .build()
-        .unwrap()
-});
-
 /// Infer the data type of a record
 fn infer_field_schema(string: &str, try_parse_dates: bool) -> DataType {
     // when quoting is enabled in the reader, these quotes aren't escaped, we default to

crates/polars-io/src/parquet/predicates.rs

@@ -1,118 +1,18 @@
-use arrow::compute::concatenate::concatenate;
 use arrow::io::parquet::read::statistics::{deserialize, Statistics};
 use arrow::io::parquet::read::RowGroupMetaData;
 use polars_core::prelude::*;
 
-use crate::predicates::PhysicalIoExpr;
+use crate::predicates::{BatchStats, ColumnStats, PhysicalIoExpr};
 use crate::ArrowResult;
 
-/// The statistics for a column in a Parquet file
-/// they typically hold
-/// - max value
-/// - min value
-/// - null_count
-#[cfg_attr(debug_assertions, derive(Debug))]
-pub struct ColumnStats(Statistics, Field);
-
 impl ColumnStats {
-    pub fn dtype(&self) -> DataType {
-        self.1.data_type().clone()
-    }
-
-    pub fn null_count(&self) -> Option<usize> {
-        match self.1.data_type() {
-            #[cfg(feature = "dtype-struct")]
-            DataType::Struct(_) => None,
-            _ => {
-                // the array holds the null count for every row group
-                // so we sum them to get them of the whole file.
-                let s = Series::try_from(("", self.0.null_count.clone())).unwrap();
-
-                // if all null, there are no statistics.
-                if s.null_count() != s.len() {
-                    s.sum()
-                } else {
-                    None
-                }
-            },
-        }
-    }
-
-    pub fn to_min_max(&self) -> Option<Series> {
-        let max_val = &*self.0.max_value;
-        let min_val = &*self.0.min_value;
-
-        let dtype = DataType::from(min_val.data_type());
-
-        if Self::use_min_max(dtype) {
-            let arr = concatenate(&[min_val, max_val]).unwrap();
-            let s = Series::try_from(("", arr)).unwrap();
-            if s.null_count() > 0 {
-                None
-            } else {
-                Some(s)
-            }
-        } else {
-            None
-        }
-    }
-
-    pub fn to_min(&self) -> Option<Series> {
-        let min_val = self.0.min_value.clone();
-        let dtype = DataType::from(min_val.data_type());
-
-        if !Self::use_min_max(dtype) || min_val.len() != 1 {
-            return None;
-        }
-
-        let s = Series::try_from(("", min_val)).unwrap();
-        if s.null_count() > 0 {
-            None
-        } else {
-            Some(s)
-        }
-    }
-
-    pub fn to_max(&self) -> Option<Series> {
-        let max_val = self.0.max_value.clone();
-        let dtype = DataType::from(max_val.data_type());
-
-        if !Self::use_min_max(dtype) || max_val.len() != 1 {
-            return None;
-        }
-
-        let s = Series::try_from(("", max_val)).unwrap();
-        if s.null_count() > 0 {
-            None
-        } else {
-            Some(s)
-        }
-    }
-
-    #[cfg(feature = "dtype-binary")]
-    fn use_min_max(dtype: DataType) -> bool {
-        dtype.is_numeric() || matches!(dtype, DataType::Utf8) || matches!(dtype, DataType::Binary)
-    }
-
-    #[cfg(not(feature = "dtype-binary"))]
-    fn use_min_max(dtype: DataType) -> bool {
-        dtype.is_numeric() || matches!(dtype, DataType::Utf8)
-    }
-}
-
-/// A collection of column stats with a known schema.
-pub struct BatchStats {
-    schema: Schema,
-    stats: Vec<ColumnStats>,
-}
-
-impl BatchStats {
-    pub fn get_stats(&self, column: &str) -> polars_core::error::PolarsResult<&ColumnStats> {
-        self.schema.try_index_of(column).map(|i| &self.stats[i])
-    }
-
-    pub fn schema(&self) -> &Schema {
-        &self.schema
+    fn from_arrow_stats(stats: Statistics, field: &ArrowField) -> Self {
+        Self::new(
+            field.into(),
+            Some(Series::try_from(("", stats.null_count)).unwrap()),
+            Some(Series::try_from(("", stats.min_value)).unwrap()),
+            Some(Series::try_from(("", stats.max_value)).unwrap()),
+        )
     }
 }
 
@@ -133,13 +33,13 @@ pub(crate) fn collect_statistics(
             Some(rg) => deserialize(fld, &md[rg..rg + 1])?,
         };
         schema.with_column((&fld.name).into(), (&fld.data_type).into());
-        stats.push(ColumnStats(st, fld.into()));
+        stats.push(ColumnStats::from_arrow_stats(st, fld));
     }
 
     Ok(if stats.is_empty() {
         None
     } else {
-        Some(BatchStats { schema, stats })
+        Some(BatchStats::new(schema, stats))
     })
 }
 

crates/polars-io/src/parquet/read.rs

@@ -52,6 +52,7 @@ pub struct ParquetReader<R: Read + Seek> {
     row_count: Option<RowCount>,
     low_memory: bool,
     metadata: Option<FileMetaData>,
+    hive_partition_columns: Option<Vec<Series>>,
     use_statistics: bool,
 }
 
@@ -78,6 +79,7 @@ impl<R: MmapBytesReader> ParquetReader<R> {
             self.parallel,
             self.row_count,
             self.use_statistics,
+            self.hive_partition_columns.as_deref(),
         )
         .map(|mut df| {
             if rechunk {
@@ -145,6 +147,11 @@ impl<R: MmapBytesReader> ParquetReader<R> {
         Ok(metadata.num_rows)
     }
 
+    pub fn with_hive_partition_columns(mut self, columns: Option<Vec<Series>>) -> Self {
+        self.hive_partition_columns = columns;
+        self
+    }
+
     fn get_metadata(&mut self) -> PolarsResult<&FileMetaData> {
         if self.metadata.is_none() {
             self.metadata = Some(read::read_metadata(&mut self.reader)?);
@@ -166,6 +173,7 @@ impl<R: MmapBytesReader + 'static> ParquetReader<R> {
             self.row_count,
             chunk_size,
             self.use_statistics,
+            self.hive_partition_columns,
         )
     }
 }
@@ -184,6 +192,7 @@ impl<R: MmapBytesReader> SerReader<R> for ParquetReader<R> {
             low_memory: false,
             metadata: None,
             use_statistics: true,
+            hive_partition_columns: None,
         }
     }
 
@@ -210,6 +219,7 @@ impl<R: MmapBytesReader> SerReader<R> for ParquetReader<R> {
             self.parallel,
             self.row_count,
             self.use_statistics,
+            self.hive_partition_columns.as_deref(),
         )
         .map(|mut df| {
             if self.rechunk {
@@ -230,6 +240,7 @@ pub struct ParquetAsyncReader {
     projection: Option<Vec<usize>>,
     row_count: Option<RowCount>,
     use_statistics: bool,
+    hive_partition_columns: Option<Vec<Series>>,
 }
 
 #[cfg(feature = "cloud")]
@@ -245,6 +256,7 @@ impl ParquetAsyncReader {
             projection: None,
             row_count: None,
             use_statistics: true,
+            hive_partition_columns: None,
         })
     }
 
@@ -294,6 +306,11 @@ impl ParquetAsyncReader {
         self
     }
 
+    pub fn with_hive_partition_columns(mut self, columns: Option<Vec<Series>>) -> Self {
+        self.hive_partition_columns = columns;
+        self
+    }
+
     #[tokio::main(flavor = "current_thread")]
     pub async fn batched(mut self, chunk_size: usize) -> PolarsResult<BatchedParquetReader> {
         let metadata = self.reader.get_metadata().await?.to_owned();
@@ -311,6 +328,7 @@ impl ParquetAsyncReader {
             self.row_count,
             chunk_size,
             self.use_statistics,
+            self.hive_partition_columns,
         )
     }