[WIP] feat: Parsed Stats Schema

kernel/src/lib.rs

@@ -96,6 +96,7 @@ mod log_path;
 pub mod scan;
 pub mod schema;
 pub mod snapshot;
+pub mod statistics;
 pub mod table_changes;
 pub mod table_configuration;
 pub mod table_features;

kernel/src/statistics.rs

@@ -0,0 +1,48 @@
+//! Statistics types for Delta tables
+//!
+//! This module contains types for representing file statistics in both JSON and parsed formats.
+//! Statistics are used for data skipping during query execution and are stored in checkpoint files.
+
+use std::collections::HashMap;
+
+use crate::expressions::Scalar;
+
+/// Parsed statistics for a file (alternative to JSON stats string)
+///
+/// This represents the structured form of file statistics that can be stored
+/// directly in checkpoints as `stats_parsed` instead of as a JSON string.
+///
+/// The minValues, maxValues, and nullCount fields contain dynamic structs
+/// whose schema matches the table's data columns (using physical column names).
+///
+/// # Schema
+///
+/// The stats_parsed schema in checkpoints is:
+/// ```text
+/// struct<
+///   numRecords: long,
+///   minValues: struct<col1: type1, col2: type2, ...>,  // Dynamic per table
+///   maxValues: struct<col1: type1, col2: type2, ...>,  // Dynamic per table
+///   nullCount: struct<col1: long, col2: long, ...>,    // Dynamic per table
+///   tightBounds: boolean
+/// >
+/// ```
+#[derive(Debug, Clone, PartialEq)]
+pub struct StatsParsed {
+    /// Number of records in the file
+    pub num_records: Option<i64>,
+
+    /// Minimum values per column (physical column names)
+    /// Dynamic based on table schema
+    pub min_values: Option<HashMap<String, Scalar>>,
+
+    /// Maximum values per column (physical column names)
+    /// Dynamic based on table schema
+    pub max_values: Option<HashMap<String, Scalar>>,
+
+    /// Null count per column (physical column names)
+    pub null_count: Option<HashMap<String, i64>>,
+
+    /// Whether statistics are exact (tight bounds)
+    pub tight_bounds: Option<bool>,
+}