feat: add arrow_schema_utility (#301)

# Rationale for this change

There are situations where we infer arrow schemas using the official
arrow crate functions which will produce arrow schemas that are not
fully posql compatible.



# What changes are included in this PR?

This patch adds a function to give us posql compatible arrow schemas:
arrow_schema_utility::get_posql_compatible_schema()

# Are these changes tested?

Yes

crates/proof-of-sql/src/base/database/arrow_schema_utility.rs

@@ -0,0 +1,37 @@
+//! This module provides utility functions for working with Arrow schemas in the context of Proof of SQL.
+//! It includes functionality to convert Arrow schemas to PoSQL-compatible formats.
+
+use alloc::sync::Arc;
+use arrow::datatypes::{DataType, Field, Schema, SchemaRef};
+
+/// Converts an Arrow schema to a PoSQL-compatible schema.
+///
+/// This function takes an Arrow `SchemaRef` and returns a new `SchemaRef` where
+/// floating-point data types (Float16, Float32, Float64) are converted to Decimal256(75, 30).
+/// Other data types remain unchanged.
+///
+/// # Arguments
+///
+/// * `schema` - The input Arrow schema to convert.
+///
+/// # Returns
+///
+/// A new `SchemaRef` with PoSQL-compatible data types.
+#[must_use]
+pub fn get_posql_compatible_schema(schema: &SchemaRef) -> SchemaRef {
+    let new_fields: Vec<Field> = schema
+        .fields()
+        .iter()
+        .map(|field| {
+            let new_data_type = match field.data_type() {
+                DataType::Float16 | DataType::Float32 | DataType::Float64 => {
+                    DataType::Decimal256(75, 30)
+                }
+                _ => field.data_type().clone(),
+            };
+            Field::new(field.name(), new_data_type, field.is_nullable())
+        })
+        .collect();
+
+    Arc::new(Schema::new(new_fields))
+}

crates/proof-of-sql/src/base/database/mod.rs

@@ -31,6 +31,9 @@ mod record_batch_utility;
 #[cfg(feature = "arrow")]
 pub use record_batch_utility::ToArrow;
 
+#[cfg(feature = "arrow")]
+pub mod arrow_schema_utility;
+
 #[cfg(all(test, feature = "arrow", feature = "test"))]
 mod test_accessor_utility;
 #[cfg(all(test, feature = "arrow", feature = "test"))]