fix: get_storage_timestamp/lock_for_read should ignore PRETOUCH_DT (#2067)

Closes STOR-484

Author: pjenvey

syncstorage-db/src/tests/batch.rs

@@ -374,3 +374,20 @@ async fn test_append_async_w_empty_string() -> Result<(), DbError> {
     })
     .await
 }
+
+#[tokio::test]
+async fn pretouch() -> Result<(), DbError> {
+    let settings = Settings::test_settings().syncstorage;
+    with_test_transaction(settings, async |db: &mut dyn Db<Error = DbError>| {
+        let uid = 1;
+        let coll = "clients";
+        db.delete_storage(hid(uid)).await?;
+        let _batch = db.create_batch(cb(uid, coll, vec![])).await?;
+        // client with no timestamp (or PRETOUCH on some backends) should act as if
+        // no timestamp exists
+        let ts = db.get_storage_timestamp(hid(uid)).await?;
+        assert_eq!(ts, SyncTimestamp::zero());
+        Ok(())
+    })
+    .await
+}

syncstorage-postgres/src/db/db_impl.rs

@@ -98,6 +98,7 @@ impl Db for PgDb {
             .select(user_collections::modified)
             .filter(user_collections::user_id.eq(user_id))
             .filter(user_collections::collection_id.eq(collection_id))
+            .filter(user_collections::modified.gt(PRETOUCH_DT))
             .for_share()
             .first(&mut self.conn)
             .await
@@ -235,6 +236,7 @@ impl Db for PgDb {
         let modified = user_collections::table
             .select(max(user_collections::modified))
             .filter(user_collections::user_id.eq(params.legacy_id as i64))
+            .filter(user_collections::modified.gt(PRETOUCH_DT))
             .first::<Option<_>>(&mut self.conn)
             .await?
             .unwrap_or_else(SyncTimestamp::zero);