result: replace col_specs with col_names

Currently, we heavily depend on the fact that `QueryResult::col_specs()`
returns a  `&[ColumnSpec<'static>]`. This won't be true once we bump
rust-driver dependency to 0.15 - the lifetime of ColumnSpec will be tied
to the lifetime of `QueryRowsResult` object.

It looks like most of the information held by `col_spec` was reduntant.
It was only used to retrieve the name of the column. This is why, we will
only hold the information about the column names. The column types are
stored in `col_data_types`.

This also allows us to get rid of `'static` bound from `CassResultData::from_result_payload`.
It will be helpful when bumping to 0.15.

As a bonus, we can also replace the `Vec<>` with a slice `&[]` in
`from_result_payload`, since we do not need to own the column specs anymore.

Author: muzarski

scylla-rust-wrapper/src/query_result.rs

@@ -24,13 +24,13 @@ pub struct CassResult {
 }
 
 pub struct CassResultData {
-    pub col_specs: Vec<ColumnSpec<'static>>,
+    pub col_names: Vec<String>,
     pub col_data_types: Arc<Vec<Arc<CassDataType>>>,
 }
 
 impl CassResultData {
     pub fn from_result_payload(
-        col_specs: Vec<ColumnSpec<'static>>,
+        col_specs: &[ColumnSpec<'_>],
         maybe_col_data_types: Option<Arc<Vec<Arc<CassDataType>>>>,
     ) -> CassResultData {
         // `maybe_col_data_types` is:
@@ -46,8 +46,13 @@ impl CassResultData {
             )
         });
 
+        let col_names = col_specs
+            .iter()
+            .map(|col_spec| col_spec.name().to_owned())
+            .collect();
+
         CassResultData {
-            col_specs,
+            col_names,
             col_data_types,
         }
     }
@@ -895,12 +900,12 @@ pub unsafe extern "C" fn cass_row_get_column_by_name_n(
 
     return row_from_raw
         .result_metadata
-        .col_specs
+        .col_names
         .iter()
         .enumerate()
-        .find(|(_, spec)| {
-            is_case_sensitive && spec.name() == name_str
-                || !is_case_sensitive && spec.name().eq_ignore_ascii_case(name_str)
+        .find(|(_, col_name)| {
+            is_case_sensitive && *col_name == name_str
+                || !is_case_sensitive && col_name.eq_ignore_ascii_case(name_str)
         })
         .map(|(index, _)| {
             return match row_from_raw.columns.get(index) {
@@ -921,12 +926,11 @@ pub unsafe extern "C" fn cass_result_column_name(
     let result_from_raw = ptr_to_ref(result);
     let index_usize: usize = index.try_into().unwrap();
 
-    if index_usize >= result_from_raw.metadata.col_specs.len() {
+    if index_usize >= result_from_raw.metadata.col_data_types.len() {
         return CassError::CASS_ERROR_LIB_INDEX_OUT_OF_BOUNDS;
     }
 
-    let column_spec: &ColumnSpec = result_from_raw.metadata.col_specs.get(index_usize).unwrap();
-    let column_name = column_spec.name();
+    let column_name = result_from_raw.metadata.col_names.get(index_usize).unwrap();
 
     write_str_to_c(column_name, name, name_length);
 
@@ -1334,7 +1338,7 @@ pub unsafe extern "C" fn cass_result_row_count(result_raw: *const CassResult) ->
 pub unsafe extern "C" fn cass_result_column_count(result_raw: *const CassResult) -> size_t {
     let result = ptr_to_ref(result_raw);
 
-    result.metadata.col_specs.len() as size_t
+    result.metadata.col_data_types.len() as size_t
 }
 
 #[no_mangle]
@@ -1411,7 +1415,7 @@ mod tests {
     const THIRD_COLUMN_NAME: &str = "list_double_col";
     fn create_cass_rows_result() -> CassResult {
         let metadata = Arc::new(CassResultData::from_result_payload(
-            vec![
+            &[
                 col_spec(FIRST_COLUMN_NAME, ColumnType::BigInt),
                 col_spec(SECOND_COLUMN_NAME, ColumnType::Varint),
                 col_spec(
@@ -1528,7 +1532,7 @@ mod tests {
     }
 
     fn create_non_rows_cass_result() -> CassResult {
-        let metadata = Arc::new(CassResultData::from_result_payload(vec![], None));
+        let metadata = Arc::new(CassResultData::from_result_payload(&[], None));
         CassResult {
             rows: None,
             metadata,

scylla-rust-wrapper/src/session.rs

@@ -220,7 +220,7 @@ pub unsafe extern "C" fn cass_session_execute_batch(
         match query_res {
             Ok(_result) => Ok(CassResultValue::QueryResult(Arc::new(CassResult {
                 rows: None,
-                metadata: Arc::new(CassResultData::from_result_payload(vec![], None)),
+                metadata: Arc::new(CassResultData::from_result_payload(&[], None)),
                 tracing_id: None,
                 paging_state_response: PagingStateResponse::NoMorePages,
             }))),
@@ -355,7 +355,7 @@ pub unsafe extern "C" fn cass_session_execute(
         match query_res {
             Ok((result, paging_state_response, maybe_col_data_types)) => {
                 let metadata = Arc::new(CassResultData::from_result_payload(
-                    result.col_specs().to_vec(),
+                    result.col_specs(),
                     maybe_col_data_types,
                 ));
                 let cass_rows = result