Implement row group skipping for the default engine parquet readers

ffi/src/engine_funcs.rs

@@ -122,6 +122,7 @@ fn read_parquet_file_impl(
         last_modified: file.last_modified,
         size: file.size,
     };
+    // TODO: Plumb the predicate through the FFI?
     let data = parquet_handler.read_parquet_files(&[delta_fm], physical_schema, None)?;
     let res = Box::new(FileReadResultIterator {
         data,

kernel/src/engine/default/parquet.rs

@@ -14,6 +14,7 @@ use parquet::arrow::async_reader::{ParquetObjectReader, ParquetRecordBatchStream
 use super::file_stream::{FileOpenFuture, FileOpener, FileStream};
 use crate::engine::arrow_utils::{generate_mask, get_requested_indices, reorder_struct_array};
 use crate::engine::default::executor::TaskExecutor;
+use crate::engine::parquet_row_group_skipping::ParquetRowGroupSkipping;
 use crate::schema::SchemaRef;
 use crate::{DeltaResult, Error, Expression, FileDataReadResultIterator, FileMeta, ParquetHandler};
 
@@ -47,7 +48,7 @@ impl<E: TaskExecutor> ParquetHandler for DefaultParquetHandler<E> {
         &self,
         files: &[FileMeta],
         physical_schema: SchemaRef,
-        _predicate: Option<Expression>,
+        predicate: Option<Expression>,
     ) -> DeltaResult<FileDataReadResultIterator> {
         if files.is_empty() {
             return Ok(Box::new(std::iter::empty()));
@@ -62,10 +63,15 @@ impl<E: TaskExecutor> ParquetHandler for DefaultParquetHandler<E> {
         //   -> parse to parquet
         // SAFETY: we did is_empty check above, this is ok.
         let file_opener: Box<dyn FileOpener> = match files[0].location.scheme() {
-            "http" | "https" => Box::new(PresignedUrlOpener::new(1024, physical_schema.clone())),
+            "http" | "https" => Box::new(PresignedUrlOpener::new(
+                1024,
+                physical_schema.clone(),
+                predicate,
+            )),
             _ => Box::new(ParquetOpener::new(
                 1024,
                 physical_schema.clone(),
+                predicate,
                 self.store.clone(),
             )),
         };
@@ -83,20 +89,23 @@ impl<E: TaskExecutor> ParquetHandler for DefaultParquetHandler<E> {
 struct ParquetOpener {
     // projection: Arc<[usize]>,
     batch_size: usize,
-    limit: Option<usize>,
     table_schema: SchemaRef,
+    predicate: Option<Expression>,
+    limit: Option<usize>,
     store: Arc<DynObjectStore>,
 }
 
 impl ParquetOpener {
     pub(crate) fn new(
         batch_size: usize,
         table_schema: SchemaRef,
+        predicate: Option<Expression>,
         store: Arc<DynObjectStore>,
     ) -> Self {
         Self {
             batch_size,
             table_schema,
+            predicate,
             limit: None,
             store,
         }
@@ -111,6 +120,7 @@ impl FileOpener for ParquetOpener {
         let batch_size = self.batch_size;
         // let projection = self.projection.clone();
         let table_schema = self.table_schema.clone();
+        let predicate = self.predicate.clone();
         let limit = self.limit;
 
         Ok(Box::pin(async move {
@@ -133,6 +143,9 @@ impl FileOpener for ParquetOpener {
                 builder = builder.with_projection(mask)
             }
 
+            if let Some(ref predicate) = predicate {
+                builder = builder.with_row_group_filter(predicate);
+            }
             if let Some(limit) = limit {
                 builder = builder.with_limit(limit)
             }
@@ -153,16 +166,18 @@ impl FileOpener for ParquetOpener {
 /// Implements [`FileOpener`] for a opening a parquet file from a presigned URL
 struct PresignedUrlOpener {
     batch_size: usize,
+    predicate: Option<Expression>,
     limit: Option<usize>,
     table_schema: SchemaRef,
     client: reqwest::Client,
 }
 
 impl PresignedUrlOpener {
-    pub(crate) fn new(batch_size: usize, schema: SchemaRef) -> Self {
+    pub(crate) fn new(batch_size: usize, schema: SchemaRef, predicate: Option<Expression>) -> Self {
         Self {
             batch_size,
             table_schema: schema,
+            predicate,
             limit: None,
             client: reqwest::Client::new(),
         }
@@ -173,6 +188,7 @@ impl FileOpener for PresignedUrlOpener {
     fn open(&self, file_meta: FileMeta, _range: Option<Range<i64>>) -> DeltaResult<FileOpenFuture> {
         let batch_size = self.batch_size;
         let table_schema = self.table_schema.clone();
+        let predicate = self.predicate.clone();
         let limit = self.limit;
         let client = self.client.clone(); // uses Arc internally according to reqwest docs
 
@@ -196,6 +212,9 @@ impl FileOpener for PresignedUrlOpener {
                 builder = builder.with_projection(mask)
             }
 
+            if let Some(ref predicate) = predicate {
+                builder = builder.with_row_group_filter(predicate);
+            }
             if let Some(limit) = limit {
                 builder = builder.with_limit(limit)
             }
@@ -261,6 +280,7 @@ mod tests {
             size: meta.size,
         }];
 
+        // TODO: add a test that uses predicate skipping?
         let handler = DefaultParquetHandler::new(store, Arc::new(TokioBackgroundExecutor::new()));
         let data: Vec<RecordBatch> = handler
             .read_parquet_files(files, Arc::new(physical_schema.try_into().unwrap()), None)

kernel/src/engine/mod.rs

@@ -11,6 +11,9 @@ pub mod arrow_expression;
 #[cfg(any(feature = "default-engine", feature = "sync-engine"))]
 pub mod arrow_data;
 
+#[cfg(any(feature = "default-engine", feature = "sync-engine"))]
+pub mod parquet_row_group_skipping;
+
 #[cfg(any(feature = "default-engine", feature = "sync-engine"))]
 pub mod parquet_stats_skipping;
 

kernel/src/engine/parquet_row_group_skipping.rs

@@ -0,0 +1,207 @@
+//! An implementation of parquet row group skipping using data skipping predicates over footer stats.
+use crate::engine::parquet_stats_skipping::{col_name_to_path, ParquetStatsSkippingFilter};
+use crate::expressions::{Expression, Scalar};
+use crate::schema::{DataType, PrimitiveType};
+use parquet::arrow::arrow_reader::ArrowReaderBuilder;
+use parquet::file::metadata::RowGroupMetaData;
+use parquet::file::statistics::Statistics;
+use parquet::schema::types::{ColumnDescPtr, ColumnPath};
+use std::collections::{HashMap, HashSet};
+
+#[cfg(test)]
+mod tests;
+
+/// An extension trait for [`ArrowReaderBuilder`] that injects row group skipping capability.
+pub(crate) trait ParquetRowGroupSkipping {
+    /// Instructs the parquet reader to perform row group skipping, eliminating any row group whose
+    /// stats prove that none of the group's rows can satisfy the given `predicate`.
+    fn with_row_group_filter(self, predicate: &Expression) -> Self;
+}
+impl<T> ParquetRowGroupSkipping for ArrowReaderBuilder<T> {
+    fn with_row_group_filter(self, predicate: &Expression) -> Self {
+        let indices = self
+            .metadata()
+            .row_groups()
+            .iter()
+            .enumerate()
+            .filter_map(|(index, row_group)| {
+                // If the group survives the filter, return Some(index) so filter_map keeps it.
+                RowGroupFilter::apply(row_group, predicate).then_some(index)
+            })
+            .collect();
+        self.with_row_groups(indices)
+    }
+}
+
+/// A ParquetStatsSkippingFilter for row group skipping. It obtains stats from a parquet
+/// [`RowGroupMetaData`] and pre-computes the mapping of each referenced column path to its
+/// corresponding field index, for O(1) stats lookups.
+struct RowGroupFilter<'a> {
+    row_group: &'a RowGroupMetaData,
+    field_indices: HashMap<ColumnPath, usize>,
+}
+
+impl<'a> RowGroupFilter<'a> {
+    /// Creates a new row group filter for the given row group and predicate.
+    fn new(row_group: &'a RowGroupMetaData, predicate: &Expression) -> Self {
+        Self {
+            row_group,
+            field_indices: compute_field_indices(row_group.schema_descr().columns(), predicate),
+        }
+    }
+
+    /// Applies a filtering predicate to a row group. Return value false means to skip it.
+    fn apply(row_group: &'a RowGroupMetaData, predicate: &Expression) -> bool {
+        let result = RowGroupFilter::new(row_group, predicate).apply_sql_where(predicate);
+        !matches!(result, Some(false))
+    }
+
+    fn get_stats(&self, col: &ColumnPath) -> Option<&Statistics> {
+        let field_index = self.field_indices.get(col)?;
+        self.row_group.column(*field_index).statistics()
+    }
+    fn decimal_from_bytes(bytes: Option<&[u8]>, p: u8, s: u8) -> Option<Scalar> {
+        // WARNING: The bytes are stored in big-endian order; reverse and then 0-pad them.
+        let bytes = bytes.filter(|b| b.len() <= 16)?;
+        let mut bytes = Vec::from(bytes);
+        bytes.reverse();
+        bytes.resize(16, 0u8);
+        let bytes: [u8; 16] = bytes.try_into().ok()?;
+        Some(Scalar::Decimal(i128::from_le_bytes(bytes), p, s))
+    }
+}
+
+impl<'a> ParquetStatsSkippingFilter for RowGroupFilter<'a> {
+    // Extracts a stat value, converting from its physical type to the requested logical type.
+    //
+    // NOTE: This code is highly redundant with [`get_min_stat_value`], but parquet
+    // ValueStatistics<T> requires T to impl a private trait, so we can't factor out any kind of
+    // helper method. And macros are hard enough to read that it's not worth defining one.
+    fn get_min_stat_value(&self, col: &ColumnPath, data_type: &DataType) -> Option<Scalar> {
+        use PrimitiveType::*;
+        let value = match (data_type.as_primitive_opt()?, self.get_stats(col)?) {
+            (String, Statistics::ByteArray(s)) => s.min_opt()?.as_utf8().ok()?.into(),
+            (String, Statistics::FixedLenByteArray(s)) => s.min_opt()?.as_utf8().ok()?.into(),
+            (String, _) => return None,
+            (Long, Statistics::Int64(s)) => s.min_opt()?.into(),
+            (Long, Statistics::Int32(s)) => (*s.min_opt()? as i64).into(),
+            (Long, _) => return None,
+            (Integer, Statistics::Int32(s)) => s.min_opt()?.into(),
+            (Integer, _) => return None,
+            (Short, Statistics::Int32(s)) => (*s.min_opt()? as i16).into(),
+            (Short, _) => return None,
+            (Byte, Statistics::Int32(s)) => (*s.min_opt()? as i8).into(),
+            (Byte, _) => return None,
+            (Float, Statistics::Float(s)) => s.min_opt()?.into(),
+            (Float, _) => return None,
+            (Double, Statistics::Double(s)) => s.min_opt()?.into(),
+            (Double, Statistics::Float(s)) => (*s.min_opt()? as f64).into(),
+            (Double, _) => return None,
+            (Boolean, Statistics::Boolean(s)) => s.min_opt()?.into(),
+            (Boolean, _) => return None,
+            (Binary, Statistics::ByteArray(s)) => s.min_opt()?.data().into(),
+            (Binary, Statistics::FixedLenByteArray(s)) => s.min_opt()?.data().into(),
+            (Binary, _) => return None,
+            (Date, Statistics::Int32(s)) => Scalar::Date(*s.min_opt()?),
+            (Date, _) => return None,
+            (Timestamp, Statistics::Int64(s)) => Scalar::Timestamp(*s.min_opt()?),
+            (Timestamp, _) => return None, // TODO: Int96 timestamps
+            (TimestampNtz, Statistics::Int64(s)) => Scalar::TimestampNtz(*s.min_opt()?),
+            (TimestampNtz, Statistics::Int32(_)) => return None, // TODO: widen from DATE
+            (TimestampNtz, _) => return None,                    // TODO: Int96 timestamps
+            (Decimal(p, s), Statistics::Int32(i)) => Scalar::Decimal(*i.min_opt()? as i128, *p, *s),
+            (Decimal(p, s), Statistics::Int64(i)) => Scalar::Decimal(*i.min_opt()? as i128, *p, *s),
+            (Decimal(p, s), Statistics::FixedLenByteArray(b)) => {
+                Self::decimal_from_bytes(b.min_bytes_opt(), *p, *s)?
+            }
+            (Decimal(..), _) => return None,
+        };
+        Some(value)
+    }
+
+    fn get_max_stat_value(&self, col: &ColumnPath, data_type: &DataType) -> Option<Scalar> {
+        use PrimitiveType::*;
+        let value = match (data_type.as_primitive_opt()?, self.get_stats(col)?) {
+            (String, Statistics::ByteArray(s)) => s.max_opt()?.as_utf8().ok()?.into(),
+            (String, Statistics::FixedLenByteArray(s)) => s.max_opt()?.as_utf8().ok()?.into(),
+            (String, _) => return None,
+            (Long, Statistics::Int64(s)) => s.max_opt()?.into(),
+            (Long, Statistics::Int32(s)) => (*s.max_opt()? as i64).into(),
+            (Long, _) => return None,
+            (Integer, Statistics::Int32(s)) => s.max_opt()?.into(),
+            (Integer, _) => return None,
+            (Short, Statistics::Int32(s)) => (*s.max_opt()? as i16).into(),
+            (Short, _) => return None,
+            (Byte, Statistics::Int32(s)) => (*s.max_opt()? as i8).into(),
+            (Byte, _) => return None,
+            (Float, Statistics::Float(s)) => s.max_opt()?.into(),
+            (Float, _) => return None,
+            (Double, Statistics::Double(s)) => s.max_opt()?.into(),
+            (Double, Statistics::Float(s)) => (*s.max_opt()? as f64).into(),
+            (Double, _) => return None,
+            (Boolean, Statistics::Boolean(s)) => s.max_opt()?.into(),
+            (Boolean, _) => return None,
+            (Binary, Statistics::ByteArray(s)) => s.max_opt()?.data().into(),
+            (Binary, Statistics::FixedLenByteArray(s)) => s.max_opt()?.data().into(),
+            (Binary, _) => return None,
+            (Date, Statistics::Int32(s)) => Scalar::Date(*s.max_opt()?),
+            (Date, _) => return None,
+            (Timestamp, Statistics::Int64(s)) => Scalar::Timestamp(*s.max_opt()?),
+            (Timestamp, _) => return None, // TODO: Int96 timestamps
+            (TimestampNtz, Statistics::Int64(s)) => Scalar::TimestampNtz(*s.max_opt()?),
+            (TimestampNtz, Statistics::Int32(_)) => return None, // TODO: widen from DATE
+            (TimestampNtz, _) => return None,                    // TODO: Int96 timestamps
+            (Decimal(p, s), Statistics::Int32(i)) => Scalar::Decimal(*i.max_opt()? as i128, *p, *s),
+            (Decimal(p, s), Statistics::Int64(i)) => Scalar::Decimal(*i.max_opt()? as i128, *p, *s),
+            (Decimal(p, s), Statistics::FixedLenByteArray(b)) => {
+                Self::decimal_from_bytes(b.max_bytes_opt(), *p, *s)?
+            }
+            (Decimal(..), _) => return None,
+        };
+        Some(value)
+    }
+
+    // Parquet nullcount stats always have the same type (u64), so we can directly return the value
+    // instead of wrapping it in a Scalar. We can safely cast it from u64 to i64, because the
+    // nullcount can never be larger than the rowcount, and the parquet rowcount stat is i64.
+    fn get_nullcount_stat_value(&self, col: &ColumnPath) -> Option<i64> {
+        Some(self.get_stats(col)?.null_count_opt()? as i64)
+    }
+
+    fn get_rowcount_stat_value(&self) -> i64 {
+        self.row_group.num_rows()
+    }
+}
+
+/// Given a filter expression of interest and a set of parquet column descriptors, build a column ->
+/// index mapping for columns the expression references. This ensures O(1) lookup times, for an
+/// overall O(n) cost to evaluate an expression tree with n nodes.
+pub(crate) fn compute_field_indices(
+    fields: &[ColumnDescPtr],
+    expression: &Expression,
+) -> HashMap<ColumnPath, usize> {
+    fn do_recurse(expression: &Expression, cols: &mut HashSet<ColumnPath>) {
+        use Expression::*;
+        let mut recurse = |expr| do_recurse(expr, cols); // less arg passing below
+        match expression {
+            Literal(_) => {}
+            Column(name) => drop(cols.insert(col_name_to_path(name))),
+            Struct(fields) => fields.iter().for_each(recurse),
+            UnaryOperation { expr, .. } => recurse(expr),
+            BinaryOperation { left, right, .. } => [left, right].iter().for_each(|e| recurse(e)),
+            VariadicOperation { exprs, .. } => exprs.iter().for_each(recurse),
+        }
+    }
+
+    // Build up a set of requested column paths, then take each found path as the corresponding map
+    // key (avoids unnecessary cloning).
+    //
+    // NOTE: If a requested column was not available, it is silently ignored.
+    let mut requested_columns = HashSet::new();
+    do_recurse(expression, &mut requested_columns);
+    fields
+        .iter()
+        .enumerate()
+        .filter_map(|(i, f)| requested_columns.take(f.path()).map(|path| (path, i)))
+        .collect()
+}