refactor!: remove Indexes (spaceandtimelabs#252)

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# Rationale for this change
`Indexes` is not useful since we only use dense indexes from 0 to output
table length anyway. Now it is time to remove it.
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your changes and offer better suggestions for fixes.

 Example:
 Add `NestedLoopJoinExec`.
 Closes spaceandtimelabs#345.

Since we added `HashJoinExec` in spaceandtimelabs#323 it has been possible to do
provable inner joins. However performance is not satisfactory in some
cases. Hence we need to fix the problem by implement
`NestedLoopJoinExec` and speed up the code
 for `HashJoinExec`.
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# What changes are included in this PR?
- remove `Indexes`
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- Add `NestedLoopJoinExec`.
- Speed up `HashJoinExec`.
- Route joins to `NestedLoopJoinExec` if the outer input is sufficiently
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# Are these changes tested?
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Yes

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

@@ -68,10 +68,5 @@ pub(crate) use result_element_serialization::{
     decode_and_convert, decode_multiple_elements, ProvableResultElement,
 };
 
-mod indexes;
-pub(crate) use indexes::Indexes;
-#[cfg(test)]
-mod indexes_test;
-
 mod result_builder;
 pub(crate) use result_builder::ResultBuilder;

crates/proof-of-sql/src/sql/proof/proof_builder_test.rs

@@ -6,7 +6,7 @@ use crate::{
         polynomial::{compute_evaluation_vector, CompositePolynomial, MultilinearExtension},
         scalar::Curve25519Scalar,
     },
-    sql::proof::{Indexes, SumcheckSubpolynomialType},
+    sql::proof::SumcheckSubpolynomialType,
 };
 use alloc::sync::Arc;
 #[cfg(feature = "arrow")]
@@ -136,10 +136,9 @@ fn we_can_form_an_aggregated_sumcheck_polynomial() {
 #[cfg(feature = "arrow")]
 #[test]
 fn we_can_form_the_provable_query_result() {
-    let result_indexes = Indexes::Sparse(vec![1, 2]);
-    let col1: Column<Curve25519Scalar> = Column::BigInt(&[10_i64, 11, 12]);
-    let col2: Column<Curve25519Scalar> = Column::BigInt(&[-2_i64, -3, -4]);
-    let res = ProvableQueryResult::new(&result_indexes, &[col1, col2]);
+    let col1: Column<Curve25519Scalar> = Column::BigInt(&[11_i64, 12]);
+    let col2: Column<Curve25519Scalar> = Column::BigInt(&[-3_i64, -4]);
+    let res = ProvableQueryResult::new(2, &[col1, col2]);
 
     let column_fields = vec![
         ColumnField::new("a".parse().unwrap(), ColumnType::BigInt),