Ensure portdb selects _all_ rows with negative rowids (#13226)

matrix-org · Jul 11, 2022 · 28d96cb · 28d96cb
1 parent 739adf1
commit 28d96cb
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diff --git a/changelog.d/13226.bugfix b/changelog.d/13226.bugfix
@@ -0,0 +1 @@
+Fix a long-standing bug where the `synapse_port_db` script could fail to copy rows with negative row ids.
diff --git a/synapse/_scripts/synapse_port_db.py b/synapse/_scripts/synapse_port_db.py
@@ -418,12 +418,15 @@ async def handle_table(
             self.progress.update(table, table_size)  # Mark table as done
             return
 
+        # We sweep over rowids in two directions: one forwards (rowids 1, 2, 3, ...)
+        # and another backwards (rowids 0, -1, -2, ...).
         forward_select = (
             "SELECT rowid, * FROM %s WHERE rowid >= ? ORDER BY rowid LIMIT ?" % (table,)
         )
 
         backward_select = (
-            "SELECT rowid, * FROM %s WHERE rowid <= ? ORDER BY rowid LIMIT ?" % (table,)
+            "SELECT rowid, * FROM %s WHERE rowid <= ? ORDER BY rowid DESC LIMIT ?"
+            % (table,)
         )
 
         do_forward = [True]