graph: Allow remove followed by remove in write batches

If subgraphs delete entities without checking if they exist, we get two
removes in a row. In the database, the second remove would just lead to a
query that changes nothing. We'll do the same when putting a write batch
together.

Fixes #5449

Author: lutter

graph/src/components/store/write.rs

@@ -439,7 +439,7 @@ impl RowGroup {
             // clamping an old version
             match (&*prev_row, &row) {
                 (Insert { end: None, .. } | Overwrite { end: None, .. }, Insert { .. })
-                | (Remove { .. }, Overwrite { .. } | Remove { .. })
+                | (Remove { .. }, Overwrite { .. })
                 | (
                     Insert { end: Some(_), .. } | Overwrite { end: Some(_), .. },
                     Overwrite { .. } | Remove { .. },
@@ -450,6 +450,11 @@ impl RowGroup {
                         row
                     ))
                 }
+                (Remove { .. }, Remove { .. }) => {
+                    // Ignore the new row, since prev_row is already a
+                    // delete. This can happen when subgraphs delete
+                    // entities without checking if they even exist
+                }
                 (
                     Insert { end: Some(_), .. } | Overwrite { end: Some(_), .. } | Remove { .. },
                     Insert { .. },