Avoid permission checks for masked columns when the table doesn't have any

patch by Francisco Guerrero; reviewed by Shailaja Koppu, Caleb Rackliffe, Dmitry Konstantinov for CASSANDRA-21299

Author: frankgh

CHANGES.txt

@@ -1,4 +1,5 @@
 6.0-alpha2
+ * Avoid permission checks for masked columns when the table doesn't have any (CASSANDRA-21299)
  * Reduce allocations and array copies due to buffer resizing in LocalDataResponse during row serialization (CASSANDRA-21285)
  * Implement a guardrail for client driver versions (CASSANDRA-21146)
  * Enable IAuthenticator to declare supported and alterable role options (CASSANDRA-20834)

src/java/org/apache/cassandra/cql3/statements/SelectStatement.java

@@ -321,7 +321,8 @@ public void authorize(ClientState state) throws InvalidRequestException, Unautho
         for (Function function : getFunctions())
             state.ensurePermission(Permission.EXECUTE, function);
 
-        if (!state.hasTablePermission(table, Permission.UNMASK) &&
+        if (table.hasMaskedColumns() &&
+            !state.hasTablePermission(table, Permission.UNMASK) &&
             !state.hasTablePermission(table, Permission.SELECT_MASKED))
         {
             List<ColumnMetadata> queriedMaskedColumns = table.columns()

src/java/org/apache/cassandra/schema/TableMetadata.java

@@ -223,6 +223,9 @@ public enum Kind
     public final List<ColumnMetadata> columnsWithConstraints;
     public final List<ColumnMetadata> notNullColumns;
 
+    // remember whether there are masked columns or not
+    private final boolean hasMaskedColumns;
+
     protected TableMetadata(Builder builder)
     {
         flags = Sets.immutableEnumSet(builder.flags);
@@ -285,6 +288,7 @@ else if (isIndex())
 
         List<ColumnMetadata> columnsWithConstraints = new ArrayList<>();
         List<ColumnMetadata> notNullColumns = new ArrayList<>();
+        boolean hasMaskedColumns = false;
 
         for (ColumnMetadata column : this.columns())
         {
@@ -295,7 +299,10 @@ else if (isIndex())
                     notNullColumns.add(column);
 
             }
+            if (column.isMasked())
+                hasMaskedColumns = true;
         }
+        this.hasMaskedColumns = hasMaskedColumns;
         this.columnsWithConstraints = columnsWithConstraints;
         this.notNullColumns = notNullColumns;
     }
@@ -584,12 +591,7 @@ public boolean hasStaticColumns()
      */
     public boolean hasMaskedColumns()
     {
-        for (ColumnMetadata column : columns.values())
-        {
-            if (column.isMasked())
-                return true;
-        }
-        return false;
+        return hasMaskedColumns;
     }
 
     /**