Optimize save_report_lines a bit

This avoids some intermediate allocations in particular for a `flag_map` case, as well as avoiding another allocation.

In other cases its unfortunately not possible to avoid more intermediate allocations.

core/src/parsers/pyreport/utils.rs

@@ -78,7 +78,7 @@ fn create_model_sets_for_line_session<R: Report, B: ReportBuilder<R>>(
     coverage_type: &models::CoverageType,
     line_no: i64,
     datapoint: Option<&CoverageDatapoint>,
-    ctx: &mut ParseCtx<R, B>,
+    ctx: &ParseCtx<R, B>,
 ) -> LineSessionModels {
     let source_file_id = ctx.report_json_files[&ctx.chunk.index];
     let (hits, hit_branches, total_branches) = separate_pyreport_coverage(&line_session.coverage);
@@ -184,32 +184,30 @@ fn create_model_sets_for_line_session<R: Report, B: ReportBuilder<R>>(
     }
 }
 
-fn create_model_sets_for_report_line<R: Report, B: ReportBuilder<R>>(
-    report_line: &ReportLine,
-    ctx: &mut ParseCtx<R, B>,
-) -> Vec<LineSessionModels> {
+fn create_model_sets_for_report_line<'a, R: Report, B: ReportBuilder<R>>(
+    report_line: &'a ReportLine,
+    ctx: &'a ParseCtx<R, B>,
+) -> impl Iterator<Item = LineSessionModels> + 'a {
     // A `ReportLine` is a collection of `LineSession`s, and each `LineSession` has
     // a set of models we need to insert for it. Build a list of those sets of
     // models.
-    let mut line_session_models = vec![];
-    for line_session in &report_line.sessions {
+    report_line.sessions.iter().map(|session| {
         // Datapoints are effectively `LineSession`-scoped, but they don't actually live
         // in the `LineSession`. Get the `CoverageDatapoint` for this
         // `LineSession` if there is one.
         let datapoint = if let Some(Some(datapoints)) = &report_line.datapoints {
-            datapoints.get(&(line_session.session_id as u32))
+            datapoints.get(&(session.session_id as u32))
         } else {
             None
         };
-        line_session_models.push(create_model_sets_for_line_session(
-            line_session,
+        create_model_sets_for_line_session(
+            session,
             &report_line.coverage_type,
             report_line.line_no,
             datapoint,
             ctx,
-        ));
-    }
-    line_session_models
+        )
+    })
 }
 
 /// Each [`ReportLine`] from a chunks file is comprised of a number of
@@ -231,12 +229,9 @@ pub fn save_report_lines<R: Report, B: ReportBuilder<R>>(
     // assigned as a side-effect of this insertion. That lets us populate the
     // `local_sample_id` foreign key on all of the models associated with each
     // `CoverageSample`.
-    ctx.db.report_builder.multi_insert_coverage_sample(
-        models
-            .iter_mut()
-            .map(|LineSessionModels { sample, .. }| sample)
-            .collect(),
-    )?;
+    ctx.db
+        .report_builder
+        .multi_insert_coverage_sample(models.iter_mut().map(|m| &mut m.sample))?;
 
     // Populate `local_sample_id` and insert all of the context assocs for each
     // `LineSession` (if there are any)
@@ -921,10 +916,11 @@ mod tests {
             datapoints: None,
         };
 
-        let model_sets = create_model_sets_for_report_line(&report_line, parse_ctx);
+        let model_sets: Vec<_> =
+            create_model_sets_for_report_line(&report_line, parse_ctx).collect();
         assert_eq!(
             model_sets,
-            vec![
+            &[
                 LineSessionModels {
                     sample: models::CoverageSample {
                         raw_upload_id: 123,
@@ -1018,10 +1014,11 @@ mod tests {
             datapoints: Some(Some(datapoints)),
         };
 
-        let model_sets = create_model_sets_for_report_line(&report_line, parse_ctx);
+        let model_sets: Vec<_> =
+            create_model_sets_for_report_line(&report_line, parse_ctx).collect();
         assert_eq!(
             model_sets,
-            vec![
+            &[
                 LineSessionModels {
                     sample: models::CoverageSample {
                         raw_upload_id: 123,

core/src/report/mod.rs

@@ -63,9 +63,9 @@ pub trait ReportBuilder<R: Report> {
     /// passed-in models' `local_sample_id` fields are ignored and overwritten
     /// with values that are unique among all `CoverageSample`s with the same
     /// `raw_upload_id`.
-    fn multi_insert_coverage_sample(
+    fn multi_insert_coverage_sample<'a>(
         &mut self,
-        samples: Vec<&mut models::CoverageSample>,
+        samples: impl ExactSizeIterator<Item = &'a mut models::CoverageSample>,
     ) -> Result<()>;
 
     /// Create a [`models::BranchesData`] record and return it. The passed-in

core/src/report/sqlite/models.rs

@@ -102,9 +102,11 @@ pub trait Insertable {
         Ok(())
     }
 
-    fn multi_insert<'a, I>(mut models: I, conn: &rusqlite::Connection) -> Result<()>
+    fn multi_insert<'a>(
+        mut models: impl ExactSizeIterator<Item = &'a Self>,
+        conn: &rusqlite::Connection,
+    ) -> Result<()>
     where
-        I: Iterator<Item = &'a Self> + ExactSizeIterator,
         Self: 'a,
     {
         let chunk_size = Self::maximum_chunk_size(conn);

core/src/report/sqlite/report_builder.rs

@@ -95,9 +95,9 @@ impl ReportBuilder<SqliteReport> for SqliteReportBuilder {
         self.transaction()?.insert_coverage_sample(sample)
     }
 
-    fn multi_insert_coverage_sample(
+    fn multi_insert_coverage_sample<'a>(
         &mut self,
-        samples: Vec<&mut models::CoverageSample>,
+        samples: impl ExactSizeIterator<Item = &'a mut models::CoverageSample>,
     ) -> Result<()> {
         self.transaction()?.multi_insert_coverage_sample(samples)
     }
@@ -237,14 +237,17 @@ impl ReportBuilder<SqliteReport> for SqliteReportBuilderTx<'_> {
         Ok(sample)
     }
 
-    fn multi_insert_coverage_sample(
+    fn multi_insert_coverage_sample<'a>(
         &mut self,
-        mut samples: Vec<&mut models::CoverageSample>,
+        samples: impl ExactSizeIterator<Item = &'a mut models::CoverageSample>,
     ) -> Result<()> {
-        for sample in &mut samples {
-            sample.local_sample_id = self.id_sequence.next().unwrap();
-        }
-        models::CoverageSample::multi_insert(samples.iter().map(|v| &**v), &self.conn)?;
+        models::CoverageSample::multi_insert(
+            samples.map(|sample| {
+                sample.local_sample_id = self.id_sequence.next().unwrap();
+                &*sample
+            }),
+            &self.conn,
+        )?;
         Ok(())
     }
 
@@ -452,7 +455,7 @@ mod tests {
             .insert_raw_upload(Default::default())
             .unwrap();
 
-        let mut samples: Vec<models::CoverageSample> = vec![
+        let mut samples = vec![
             models::CoverageSample {
                 source_file_id: file.id,
                 raw_upload_id: raw_upload.id,
@@ -461,7 +464,7 @@ mod tests {
             5
         ];
         report_builder
-            .multi_insert_coverage_sample(samples.iter_mut().collect())
+            .multi_insert_coverage_sample(samples.iter_mut())
             .unwrap();
 
         let report = report_builder.build().unwrap();

core/src/test_utils/test_report.rs

@@ -93,9 +93,9 @@ impl ReportBuilder<TestReport> for TestReportBuilder {
         Ok(sample)
     }
 
-    fn multi_insert_coverage_sample(
+    fn multi_insert_coverage_sample<'a>(
         &mut self,
-        samples: Vec<&mut CoverageSample>,
+        samples: impl ExactSizeIterator<Item = &'a mut CoverageSample>,
     ) -> error::Result<()> {
         self.report
             .samples