Add the new tasks with most of the job done

crates/index-scheduler/src/scheduler/process_upgrade/mod.rs

@@ -0,0 +1,42 @@
+use meilisearch_types::{
+    milli,
+    milli::progress::{Progress, VariableNameStep},
+    tasks::{KindWithContent, Status, Task},
+    versioning::{VERSION_MAJOR, VERSION_MINOR, VERSION_PATCH},
+};
+
+use crate::{processing::UpgradeDatabaseProgress, Error, IndexScheduler, Result};
+
+impl IndexScheduler {
+    pub(super) fn process_upgrade(
+        &self,
+        progress: Progress,
+        mut tasks: Vec<Task>,
+    ) -> Result<Vec<Task>> {
+        progress.update_progress(UpgradeDatabaseProgress::EnsuringCorrectnessOfTheSwap);
+
+        // Since we should not have multiple upgrade tasks, we're only going to process the latest one:
+        let KindWithContent::UpgradeDatabase { from } = tasks.last().unwrap().kind else {
+            unreachable!()
+        };
+
+        enum UpgradeIndex {}
+        let indexes = self.index_names()?;
+
+        for (i, uid) in indexes.iter().enumerate() {
+            progress.update_progress(VariableNameStep::<UpgradeIndex>::new(
+                format!("Upgrading index `{uid}`"),
+                i as u32,
+                indexes.len() as u32,
+            ));
+            let index = self.index(uid)?;
+            milli::update::upgrade::upgrade(&index, from, progress.clone());
+        }
+
+        for task in tasks.iter_mut() {
+            task.status = Status::Succeeded;
+        }
+
+        Ok(tasks)
+    }
+}