replicators: Allow --replication-tables-ignore '*.*'

Starting Readyset with --replication-tables-ignore '*.*' will now deny
all tables.  This is intended to be useful for deployments that want to
initially start Readyset without replicating anything.

If desired, tables can still be added to a Readyset process running in
this mode via the ALTER READYSET ADD TABLES command.

Addresses: REA-5257
Change-Id: If2502611902a1e9685dbd58475f386ff66d79938
Reviewed-on: https://gerrit.readyset.name/c/readyset/+/8727
Tested-by: Buildkite CI
Reviewed-by: Jason Brown <jason.b@readyset.io>

Author: davisjc

database-utils/src/lib.rs

@@ -119,6 +119,8 @@ pub struct UpstreamConfig {
     /// schema) or `<schema>.*` (all tables in a schema) for Postgres and `<database>.<table>`
     /// for MySQL.
     ///
+    /// You can also specify "*.*" to indicate that no tables should be replicated at all.
+    ///
     /// Tables specified in the list will not be eligible to be used by caches.
     #[arg(long, env = "REPLICATION_TABLES_IGNORE")]
     #[serde(default)]

replicators/src/table_filter.rs

@@ -132,6 +132,13 @@ impl TableFilter {
         })
     }
 
+    fn deny_all() -> Self {
+        Self {
+            strategy_by_schema: HashMap::new(),
+            allow_unregistered_schemas: false,
+        }
+    }
+
     pub(crate) fn try_new(
         dialect: Dialect,
         replication_tables: Option<&str>,
@@ -148,9 +155,7 @@ impl TableFilter {
             return Ok(Self::allow_all());
         }
         if let Some("*.*") = replication_tables_ignore {
-            return Err(ReadySetError::ReplicationFailed(
-                "Cannot filter out all tables".to_string(),
-            ));
+            return Ok(Self::deny_all());
         }
 
         let allow_unregistered_schemas = replication_tables.is_none() && default_schema.is_none();
@@ -378,4 +383,16 @@ mod tests {
         assert!(!filter.should_be_processed("readyset", "t4"));
         assert!(filter.should_be_processed("readyset", "table"));
     }
+
+    #[test]
+    fn wildcard_deny_list() {
+        let filter = TableFilter::try_new(
+            readyset_sql::Dialect::MySQL,
+            None,
+            Some("*.*"),
+            Some("noria"),
+        )
+        .unwrap();
+        assert!(!filter.should_be_processed("noria", "t1"));
+    }
 }