[YSQL] Dropping a renamed table reserves a table name

[frozenspider]

Consider this simple example:

CREATE TABLE x (id int PRIMARY KEY);
ALTER TABLE x RENAME TO y;
DROP TABLE y;

-- This operation fails:
CREATE TABLE y (id int PRIMARY KEY);
-- ERROR:  Invalid argument: Invalid table definition: Timed out waiting for Table Creation

Thanks @nspiegelberg for tracking this, it happens because rename uses names map that is intended for YCQL only.
Name is freed by restarting yb-master.
He proposed this patch, which seem to do the trick:

diff --git a/src/yb/master/catalog_manager.cc b/src/yb/master/catalog_manager.cc
index 54b9d49cd..32a06f6d4 100644
--- a/src/yb/master/catalog_manager.cc
+++ b/src/yb/master/catalog_manager.cc
@@ -4085,7 +4085,9 @@ Status CatalogManager::AlterTable(const AlterTableRequestPB* req,
     }
 
     // Acquire the new table name (now we have 2 name for the same table).
-    table_names_map_[{new_namespace_id, new_table_name}] = table;
+    if (l->data().table_type() != PGSQL_TABLE_TYPE) {
+      table_names_map_[{new_namespace_id, new_table_name}] = table;
+    }
     table_pb.set_namespace_id(new_namespace_id);
     table_pb.set_name(new_table_name);
 
@@ -4177,10 +4179,7 @@ Status CatalogManager::AlterTable(const AlterTableRequestPB* req,
     TRACE("Removing (namespace, table) combination ($0, $1) from by-name map",
         namespace_id, table_name);
     std::lock_guard<LockType> l_map(lock_);
-    if (table->GetTableType() != PGSQL_TABLE_TYPE &&
-        table_names_map_.erase({namespace_id, table_name}) != 1) {
-      PANIC_RPC(rpc, "Could not remove table from map, name=" + l->data().name());
-    }
+    table_names_map_.erase({namespace_id, table_name}); // Not present if PGSQL.
   }
 
   // Update the in-memory state.

[frozenspider]

Resolved in 9d94a97