feat: EVM compatible proof plan serialization (#432)

# Rationale for this change

We need Solidity to be able to read Proof Plans.

# What changes are included in this PR?

An initial implementation of serialization for Proof Plan is added.

# Are these changes tested?
Yes

crates/proof-of-sql/src/evm_compatibility/dyn_proof_plan_serializer/constants.rs

@@ -0,0 +1,7 @@
+pub const FILTER_EXEC_NUM: u8 = 0;
+
+pub const COLUMN_EXPR_NUM: u8 = 0;
+pub const EQUALS_EXPR_NUM: u8 = 1;
+pub const LITERAL_EXPR_NUM: u8 = 2;
+
+pub const BIGINT_TYPE_NUM: u8 = 0;

crates/proof-of-sql/src/evm_compatibility/dyn_proof_plan_serializer/error.rs

@@ -0,0 +1,25 @@
+use snafu::Snafu;
+
+/// Errors that can occur during proof plan serialization.
+#[derive(Debug, Snafu)]
+#[snafu(visibility(pub(super)))]
+pub enum ProofPlanSerializationError {
+    /// Error indicating that the operation is not supported.
+    #[snafu(display("Not supported"))]
+    NotSupported,
+    /// Error indicating that there are more than 255 results in the filter.
+    #[snafu(display("More than 255 results in filter."))]
+    TooManyResults,
+    /// Error indicating that there are more than 255 tables referenced in the plan.
+    #[snafu(display("More than 255 tables referenced in the plan."))]
+    TooManyTables,
+    /// Error indicating that there are more than 255 columns referenced in the plan.
+    #[snafu(display("More than 255 columns referenced in the plan."))]
+    TooManyColumns,
+    /// Error indicating that the table was not found.
+    #[snafu(display("Table not found"))]
+    TableNotFound,
+    /// Error indicating that the column was not found.
+    #[snafu(display("Column not found"))]
+    ColumnNotFound,
+}

crates/proof-of-sql/src/evm_compatibility/dyn_proof_plan_serializer/mod.rs

@@ -0,0 +1,17 @@
+/// This module contains constants used in the proof serialization process.
+pub(super) mod constants;
+
+/// This module defines errors that can occur during proof plan serialization.
+mod error;
+
+/// This module handles the serialization of proof expressions.
+mod serialize_proof_expr;
+
+/// This module handles the serialization of proof plans.
+mod serialize_proof_plan;
+
+/// This module provides the main serializer for proof plans.
+mod serializer;
+
+pub use error::ProofPlanSerializationError;
+pub use serializer::DynProofPlanSerializer;

crates/proof-of-sql/src/evm_compatibility/dyn_proof_plan_serializer/serialize_proof_expr.rs

@@ -0,0 +1,246 @@
+use super::{
+    constants::{BIGINT_TYPE_NUM, COLUMN_EXPR_NUM, EQUALS_EXPR_NUM, LITERAL_EXPR_NUM},
+    error::{ColumnNotFoundSnafu, NotSupportedSnafu},
+    DynProofPlanSerializer, ProofPlanSerializationError,
+};
+use crate::{
+    base::{database::LiteralValue, scalar::Scalar},
+    evm_compatibility::primitive_serialize_ext::PrimitiveSerializeExt,
+    sql::proof_exprs::{ColumnExpr, DynProofExpr, EqualsExpr, LiteralExpr},
+};
+use snafu::OptionExt;
+
+impl<S: Scalar> DynProofPlanSerializer<S> {
+    pub(super) fn serialize_dyn_proof_expr(
+        self,
+        expr: &DynProofExpr,
+    ) -> Result<Self, ProofPlanSerializationError> {
+        match expr {
+            DynProofExpr::Column(column_expr) => self
+                .serialize_u8(COLUMN_EXPR_NUM)
+                .serialize_column_expr(column_expr),
+            DynProofExpr::Literal(literal_expr) => self
+                .serialize_u8(LITERAL_EXPR_NUM)
+                .serialize_literal_expr(literal_expr),
+            DynProofExpr::Equals(equals_expr) => self
+                .serialize_u8(EQUALS_EXPR_NUM)
+                .serialize_equals_expr(equals_expr),
+            _ => NotSupportedSnafu.fail(),
+        }
+    }
+
+    fn serialize_column_expr(
+        self,
+        column_expr: &ColumnExpr,
+    ) -> Result<Self, ProofPlanSerializationError> {
+        let column_number = self
+            .column_refs
+            .get(&column_expr.column_ref)
+            .copied()
+            .context(ColumnNotFoundSnafu)?;
+        Ok(self.serialize_u8(column_number))
+    }
+
+    fn serialize_literal_expr(
+        self,
+        literal_expr: &LiteralExpr,
+    ) -> Result<Self, ProofPlanSerializationError> {
+        match literal_expr.value {
+            LiteralValue::BigInt(value) => Ok(self
+                .serialize_u8(BIGINT_TYPE_NUM)
+                .serialize_scalar(value.into())),
+            _ => NotSupportedSnafu.fail(),
+        }
+    }
+
+    fn serialize_equals_expr(
+        self,
+        equals_expr: &EqualsExpr,
+    ) -> Result<Self, ProofPlanSerializationError> {
+        self.serialize_dyn_proof_expr(equals_expr.lhs.as_ref())?
+            .serialize_dyn_proof_expr(equals_expr.rhs.as_ref())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{
+        base::{
+            database::{ColumnRef, ColumnType, TableRef},
+            map::indexset,
+            scalar::test_scalar::TestScalar,
+        },
+        sql::proof_exprs::AndExpr,
+    };
+    use core::iter;
+    use itertools::Itertools;
+
+    #[test]
+    fn we_can_serialize_a_column_expr() {
+        let table_ref: TableRef = "namespace.table".parse().unwrap();
+        let column_0_ref: ColumnRef =
+            ColumnRef::new(table_ref, "column_0".parse().unwrap(), ColumnType::BigInt);
+        let column_1_ref: ColumnRef =
+            ColumnRef::new(table_ref, "column_1".parse().unwrap(), ColumnType::BigInt);
+        let column_2_ref: ColumnRef =
+            ColumnRef::new(table_ref, "column_2".parse().unwrap(), ColumnType::BigInt);
+        let serializer = DynProofPlanSerializer::<TestScalar>::try_new(
+            indexset! {},
+            indexset! { column_0_ref, column_1_ref },
+        )
+        .unwrap();
+
+        // Serialization of column 0 should result in a single byte with value 0.
+        let column_0_expr = ColumnExpr::new(column_0_ref);
+        let bytes_0 = serializer
+            .clone()
+            .serialize_column_expr(&column_0_expr)
+            .unwrap()
+            .into_bytes();
+        assert_eq!(bytes_0, vec![0]);
+
+        // Serialization of column 1 should result in a single byte with value 1.
+        let column_1_expr = ColumnExpr::new(column_1_ref);
+        let bytes_1 = serializer
+            .clone()
+            .serialize_column_expr(&column_1_expr)
+            .unwrap()
+            .into_bytes();
+        assert_eq!(bytes_1, vec![1]);
+
+        // Wrapping the column expression in a `DynProofExpr` should result in the same serialization,
+        // but with the column expression number prepended.
+        let wrapped_column_1_expr = DynProofExpr::Column(column_1_expr);
+        let wrapped_bytes_1 = serializer
+            .clone()
+            .serialize_dyn_proof_expr(&wrapped_column_1_expr)
+            .unwrap()
+            .into_bytes();
+        assert_eq!(wrapped_bytes_1, vec![COLUMN_EXPR_NUM, 1]);
+
+        // Serialization of column 2 should result in an error because there are only two columns.
+        let column_2_expr = ColumnExpr::new(column_2_ref);
+        let result = serializer.clone().serialize_column_expr(&column_2_expr);
+        assert!(matches!(
+            result,
+            Err(ProofPlanSerializationError::ColumnNotFound)
+        ));
+    }
+
+    #[test]
+    fn we_can_serialize_a_literal_expr() {
+        let serializer =
+            DynProofPlanSerializer::<TestScalar>::try_new(indexset! {}, indexset! {}).unwrap();
+
+        // Serialization of a big int literal should result in a byte with the big int type number,
+        // followed by the big int value in big-endian form, padded with leading zeros to 32 bytes.
+        let literal_bigint_expr = LiteralExpr::new(LiteralValue::BigInt(4200));
+        let bigint_bytes = serializer
+            .clone()
+            .serialize_literal_expr(&literal_bigint_expr)
+            .unwrap()
+            .into_bytes();
+        let expected_bigint_bytes = iter::empty::<u8>()
+            .chain([BIGINT_TYPE_NUM])
+            .chain([0; 30])
+            .chain([16, 104])
+            .collect_vec();
+        assert_eq!(bigint_bytes, expected_bigint_bytes);
+
+        // Wrapping the literal expression in a `DynProofExpr` should result in the same serialization,
+        // but with the literal expression number prepended.
+        let wrapped_literal_expr = DynProofExpr::Literal(literal_bigint_expr);
+        let wrapped_bytes = serializer
+            .clone()
+            .serialize_dyn_proof_expr(&wrapped_literal_expr)
+            .unwrap()
+            .into_bytes();
+        let expected_wrapped_bytes = iter::empty::<u8>()
+            .chain([LITERAL_EXPR_NUM])
+            .chain(expected_bigint_bytes)
+            .collect_vec();
+        assert_eq!(wrapped_bytes, expected_wrapped_bytes);
+
+        // Serialization of a small int literal should result in an error
+        // because only big int literals are supported so far
+        let literal_smallint_expr = LiteralExpr::new(LiteralValue::SmallInt(4200));
+        let result = serializer
+            .clone()
+            .serialize_literal_expr(&literal_smallint_expr);
+        assert!(matches!(
+            result,
+            Err(ProofPlanSerializationError::NotSupported)
+        ));
+    }
+
+    #[test]
+    fn we_can_serialize_an_equals_expr() {
+        let table_ref: TableRef = "namespace.table".parse().unwrap();
+        let column_0_ref: ColumnRef =
+            ColumnRef::new(table_ref, "column_0".parse().unwrap(), ColumnType::BigInt);
+        let serializer =
+            DynProofPlanSerializer::<TestScalar>::try_new(indexset! {}, indexset! { column_0_ref })
+                .unwrap();
+
+        let lhs = DynProofExpr::Column(ColumnExpr::new(column_0_ref));
+        let rhs = DynProofExpr::Literal(LiteralExpr::new(LiteralValue::BigInt(4200)));
+        let lhs_bytes = serializer
+            .clone()
+            .serialize_dyn_proof_expr(&lhs)
+            .unwrap()
+            .into_bytes();
+        let rhs_bytes = serializer
+            .clone()
+            .serialize_dyn_proof_expr(&rhs)
+            .unwrap()
+            .into_bytes();
+
+        // Serialization of an equals expression should result in the serialization of the left-hand side,
+        // followed by the serialization of the right-hand side.
+        let equals_expr = EqualsExpr::new(Box::new(lhs.clone()), Box::new(rhs.clone()));
+        let bytes = serializer
+            .clone()
+            .serialize_equals_expr(&equals_expr)
+            .unwrap()
+            .into_bytes();
+        let expected_bytes = iter::empty::<u8>()
+            .chain(lhs_bytes.clone())
+            .chain(rhs_bytes.clone())
+            .collect_vec();
+        assert_eq!(bytes, expected_bytes);
+
+        // Wrapping the equals expression in a `DynProofExpr` should result in the same serialization,
+        // but with the equals expression number prepended.
+        let wrapped_equals_expr = DynProofExpr::Equals(equals_expr);
+        let wrapped_bytes = serializer
+            .clone()
+            .serialize_dyn_proof_expr(&wrapped_equals_expr)
+            .unwrap()
+            .into_bytes();
+        let expected_wrapped_bytes = iter::empty::<u8>()
+            .chain([EQUALS_EXPR_NUM])
+            .chain(expected_bytes)
+            .collect_vec();
+        assert_eq!(wrapped_bytes, expected_wrapped_bytes);
+    }
+
+    #[test]
+    fn we_cannot_serialize_an_unsupported_expr() {
+        let table_ref: TableRef = "namespace.table".parse().unwrap();
+        let column_0_ref: ColumnRef =
+            ColumnRef::new(table_ref, "column_0".parse().unwrap(), ColumnType::BigInt);
+        let serializer =
+            DynProofPlanSerializer::<TestScalar>::try_new(indexset! {}, indexset! { column_0_ref })
+                .unwrap();
+
+        let lhs = DynProofExpr::Column(ColumnExpr::new(column_0_ref));
+        let rhs = DynProofExpr::Literal(LiteralExpr::new(LiteralValue::BigInt(4200)));
+        let expr = DynProofExpr::And(AndExpr::new(Box::new(lhs.clone()), Box::new(rhs.clone())));
+        let result = serializer.clone().serialize_dyn_proof_expr(&expr);
+        assert!(matches!(
+            result,
+            Err(ProofPlanSerializationError::NotSupported)
+        ));
+    }
+}