Fix comment

pingcap · Apr 5, 2019 · 6ea2ec8 · 6ea2ec8
1 parent a5f5029
commit 6ea2ec8
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/expression/expression.go b/expression/expression.go
@@ -79,7 +79,12 @@ type Expression interface {
 	// IsCorrelated checks if this expression has correlated key.
 	IsCorrelated() bool
 
-	// ConstItem checks if this expression refers to a table.
+	// ConstItem checks if this expression is constant item, regardless of query evaluation state.
+	// An expression is constant item if it:
+	// refers no tables.
+	// refers no subqueries that refers any tables.
+	// refers no non-deterministic functions.
+	// refers no statement parameters.
 	ConstItem() bool
 
 	// Decorrelate try to decorrelate the expression by schema.