feat(datafusion): Expose DataFusion statistics on an IcebergTableScan

crates/iceberg/src/scan.rs

@@ -206,27 +206,7 @@ impl<'a> TableScanBuilder<'a> {
 
     /// Build the table scan.
     pub fn build(self) -> Result<TableScan> {
-        let snapshot = match self.snapshot_id {
-            Some(snapshot_id) => self
-                .table
-                .metadata()
-                .snapshot_by_id(snapshot_id)
-                .ok_or_else(|| {
-                    Error::new(
-                        ErrorKind::DataInvalid,
-                        format!("Snapshot with id {} not found", snapshot_id),
-                    )
-                })?
-                .clone(),
-            None => self
-                .table
-                .metadata()
-                .current_snapshot()
-                .ok_or_else(|| {
-                    Error::new(ErrorKind::Unexpected, "Can't scan table without snapshots")
-                })?
-                .clone(),
-        };
+        let snapshot = self.table.snapshot(self.snapshot_id)?;
 
         let schema = snapshot.schema(self.table.metadata())?;
 

crates/iceberg/src/table.rs

@@ -24,7 +24,7 @@ use crate::inspect::MetadataTable;
 use crate::io::object_cache::ObjectCache;
 use crate::io::FileIO;
 use crate::scan::TableScanBuilder;
-use crate::spec::{TableMetadata, TableMetadataRef};
+use crate::spec::{SnapshotRef, TableMetadata, TableMetadataRef};
 use crate::{Error, ErrorKind, Result, TableIdent};
 
 /// Builder to create table scan.
@@ -201,6 +201,29 @@ impl Table {
         TableScanBuilder::new(self)
     }
 
+    /// Get the specified or latest snapshot for this table
+    pub fn snapshot(&self, snapshot_id: Option<i64>) -> Result<SnapshotRef> {
+        Ok(match snapshot_id {
+            Some(snapshot_id) => self
+                .metadata()
+                .snapshot_by_id(snapshot_id)
+                .ok_or_else(|| {
+                    Error::new(
+                        ErrorKind::DataInvalid,
+                        format!("Snapshot with id {} not found", snapshot_id),
+                    )
+                })?
+                .clone(),
+            None => self
+                .metadata()
+                .current_snapshot()
+                .ok_or_else(|| {
+                    Error::new(ErrorKind::Unexpected, "Can't scan table without snapshots")
+                })?
+                .clone(),
+        })
+    }
+
     /// Creates a metadata table which provides table-like APIs for inspecting metadata.
     /// See [`MetadataTable`] for more details.
     pub fn inspect(&self) -> MetadataTable<'_> {

crates/integration_tests/tests/shared_tests/datafusion.rs

@@ -22,32 +22,29 @@ use arrow_schema::TimeUnit;
 use datafusion::arrow::datatypes::{DataType, Field, Schema};
 use datafusion::assert_batches_eq;
 use datafusion::catalog::TableProvider;
-use datafusion::error::DataFusionError;
+use datafusion::common::stats::Precision;
+use datafusion::common::{ColumnStatistics, ScalarValue, Statistics};
+use datafusion::logical_expr::{col, lit};
 use datafusion::prelude::SessionContext;
-use iceberg::{Catalog, TableIdent};
+use iceberg::{Catalog, Result, TableIdent};
 use iceberg_catalog_rest::RestCatalog;
 use iceberg_datafusion::IcebergTableProvider;
 use parquet::arrow::PARQUET_FIELD_ID_META_KEY;
 
 use crate::get_shared_containers;
 
 #[tokio::test]
-async fn test_basic_queries() -> Result<(), DataFusionError> {
+async fn test_basic_queries() -> Result<()> {
     let fixture = get_shared_containers();
     let rest_catalog = RestCatalog::new(fixture.catalog_config.clone());
 
     let table = rest_catalog
         .load_table(&TableIdent::from_strs(["default", "types_test"]).unwrap())
-        .await
-        .unwrap();
+        .await?;
 
     let ctx = SessionContext::new();
 
-    let table_provider = Arc::new(
-        IcebergTableProvider::try_new_from_table(table)
-            .await
-            .unwrap(),
-    );
+    let table_provider = Arc::new(IcebergTableProvider::try_new_from_table(table).await?);
 
     let schema = table_provider.schema();
 
@@ -118,13 +115,15 @@ async fn test_basic_queries() -> Result<(), DataFusionError> {
         ])
     );
 
-    ctx.register_table("types_table", table_provider)?;
+    ctx.register_table("types_table", table_provider).unwrap();
 
     let batches = ctx
         .sql("SELECT * FROM types_table ORDER BY cbigint LIMIT 3")
-        .await?
+        .await
+        .unwrap()
         .collect()
-        .await?;
+        .await
+        .unwrap();
     let expected = [
         "+----------+----------+-----------+------+---------+--------+---------+----------+------------+---------------------+----------------------+---------+----------+",
         "| cboolean | ctinyint | csmallint | cint | cbigint | cfloat | cdouble | cdecimal | cdate      | ctimestamp_ntz      | ctimestamp           | cstring | cbinary  |",
@@ -137,3 +136,81 @@ async fn test_basic_queries() -> Result<(), DataFusionError> {
     assert_batches_eq!(expected, &batches);
     Ok(())
 }
+
+#[tokio::test]
+async fn test_statistics() -> Result<()> {
+    let fixture = get_shared_containers();
+    let rest_catalog = RestCatalog::new(fixture.catalog_config.clone());
+
+    // Test table statistics
+    let table = rest_catalog
+        .load_table(&TableIdent::from_strs([
+            "default",
+            "test_positional_merge_on_read_double_deletes",
+        ])?)
+        .await?;
+
+    let table_provider = IcebergTableProvider::try_new_from_table(table)
+        .await?
+        .with_computed_statistics()
+        .await;
+
+    let table_stats = table_provider.statistics();
+
+    assert_eq!(
+        table_stats,
+        Some(Statistics {
+            num_rows: Precision::Inexact(12),
+            total_byte_size: Precision::Absent,
+            column_statistics: vec![
+                ColumnStatistics {
+                    null_count: Precision::Inexact(0),
+                    max_value: Precision::Inexact(ScalarValue::Date32(Some(19428))),
+                    min_value: Precision::Inexact(ScalarValue::Date32(Some(19417))),
+                    distinct_count: Precision::Absent,
+                },
+                ColumnStatistics {
+                    null_count: Precision::Inexact(0),
+                    max_value: Precision::Inexact(ScalarValue::Int32(Some(12))),
+                    min_value: Precision::Inexact(ScalarValue::Int32(Some(1))),
+                    distinct_count: Precision::Absent,
+                },
+                ColumnStatistics {
+                    null_count: Precision::Inexact(0),
+                    max_value: Precision::Inexact(ScalarValue::Utf8View(Some("l".to_string()))),
+                    min_value: Precision::Inexact(ScalarValue::Utf8View(Some("a".to_string()))),
+                    distinct_count: Precision::Absent,
+                },
+            ],
+        })
+    );
+
+    // Test plan statistics with filtering
+    let ctx = SessionContext::new();
+    let scan = table_provider
+        .scan(
+            &ctx.state(),
+            Some(&vec![1]),
+            &[col("number").gt(lit(4))],
+            None,
+        )
+        .await
+        .unwrap();
+
+    let plan_stats = scan.statistics().unwrap();
+
+    // The estimate for the number of rows and the min value for the column are changed in response
+    // to the filtration
+    assert_eq!(plan_stats, Statistics {
+        num_rows: Precision::Inexact(8),
+        total_byte_size: Precision::Absent,
+        column_statistics: vec![ColumnStatistics {
+            null_count: Precision::Inexact(0),
+            max_value: Precision::Inexact(ScalarValue::Int32(Some(12))),
+            min_value: Precision::Inexact(ScalarValue::Int32(Some(5))),
+            distinct_count: Precision::Absent,
+        },],
+    });
+
+    Ok(())
+}

crates/integrations/datafusion/Cargo.toml

@@ -37,6 +37,7 @@ async-trait = { workspace = true }
 datafusion = { workspace = true }
 futures = { workspace = true }
 iceberg = { workspace = true }
+log = { workspace = true }
 tokio = { workspace = true }
 
 [dev-dependencies]

crates/integrations/datafusion/src/lib.rs

@@ -23,6 +23,9 @@ pub use error::*;
 
 mod physical_plan;
 mod schema;
+mod statistics;
 mod table;
+
+pub use statistics::*;
 pub use table::table_provider_factory::IcebergTableProviderFactory;
 pub use table::*;

crates/integrations/datafusion/src/physical_plan/expr_to_predicate.rs

@@ -20,7 +20,7 @@ use std::vec;
 use datafusion::logical_expr::{Expr, Operator};
 use datafusion::scalar::ScalarValue;
 use iceberg::expr::{BinaryExpression, Predicate, PredicateOperator, Reference, UnaryExpression};
-use iceberg::spec::Datum;
+use iceberg::spec::{Datum, PrimitiveLiteral, PrimitiveType};
 
 // A datafusion expression could be an Iceberg predicate, column, or literal.
 enum TransformedResult {
@@ -196,20 +196,44 @@ const MILLIS_PER_DAY: i64 = 24 * 60 * 60 * 1000;
 /// Convert a scalar value to an iceberg datum.
 fn scalar_value_to_datum(value: &ScalarValue) -> Option<Datum> {
     match value {
+        ScalarValue::Boolean(Some(v)) => Some(Datum::bool(*v)),
         ScalarValue::Int8(Some(v)) => Some(Datum::int(*v as i32)),
         ScalarValue::Int16(Some(v)) => Some(Datum::int(*v as i32)),
         ScalarValue::Int32(Some(v)) => Some(Datum::int(*v)),
         ScalarValue::Int64(Some(v)) => Some(Datum::long(*v)),
-        ScalarValue::Float32(Some(v)) => Some(Datum::double(*v as f64)),
+        ScalarValue::Float32(Some(v)) => Some(Datum::float(*v)),
         ScalarValue::Float64(Some(v)) => Some(Datum::double(*v)),
-        ScalarValue::Utf8(Some(v)) => Some(Datum::string(v.clone())),
-        ScalarValue::LargeUtf8(Some(v)) => Some(Datum::string(v.clone())),
+        ScalarValue::Utf8(Some(v))
+        | ScalarValue::Utf8View(Some(v))
+        | ScalarValue::LargeUtf8(Some(v)) => Some(Datum::string(v.clone())),
         ScalarValue::Date32(Some(v)) => Some(Datum::date(*v)),
         ScalarValue::Date64(Some(v)) => Some(Datum::date((*v / MILLIS_PER_DAY) as i32)),
         _ => None,
     }
 }
 
+/// Convert an iceberg datum to a datafusion scalar value.
+pub fn datum_to_scalar_value(datum: &Datum) -> Option<ScalarValue> {
+    match (datum.data_type(), datum.literal()) {
+        (PrimitiveType::Binary, PrimitiveLiteral::Boolean(v)) => {
+            Some(ScalarValue::Boolean(Some(*v)))
+        }
+        (PrimitiveType::Int, PrimitiveLiteral::Int(v)) => Some(ScalarValue::Int32(Some(*v))),
+        (PrimitiveType::Long, PrimitiveLiteral::Long(v)) => Some(ScalarValue::Int64(Some(*v))),
+        (PrimitiveType::Float, PrimitiveLiteral::Float(v)) => {
+            Some(ScalarValue::Float32(Some(v.into_inner())))
+        }
+        (PrimitiveType::Double, PrimitiveLiteral::Double(v)) => {
+            Some(ScalarValue::Float64(Some(v.into_inner())))
+        }
+        (PrimitiveType::String, PrimitiveLiteral::String(v)) => {
+            Some(ScalarValue::Utf8View(Some(v.clone())))
+        }
+        (PrimitiveType::Date, PrimitiveLiteral::Int(v)) => Some(ScalarValue::Date32(Some(*v))),
+        _ => None,
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use datafusion::arrow::datatypes::{DataType, Field, Schema, TimeUnit};