Disallow indexing of non-indexable columns

minisql/src/type_system.rs

@@ -30,6 +30,18 @@ pub enum IndexableValue {
     // TODO: what about null?
 }
 
+impl DbType {
+    pub fn is_indexable(&self) -> bool {
+        match self {
+            Self::String => true,
+            Self::Int => true,
+            Self::Number => false,
+            Self::Uuid => true,
+        }
+    }
+
+}
+
 impl Value {
     pub fn to_type(&self) -> DbType {
         match self {