src/gausskernel/dbmind/kernel/hypopg_index.cpp

@@ -31,6 +31,8 @@ l index HypoPG will create is not stored in any directory, but in the connection
 will not inflate any tables, nor will it affect any concurrent connections. Because it is assumed that indexes 
 don't really exist, HypoPG ensures that they will only be used with a simple EXPLAIN statement (no ANALYZE option).
 
+Virtual index does not occupy space, and can be used to evaluate the performance of sql query conveniently, 
+which helps us to understand the effect of query optimization.
 */
 #include <unistd.h>
 #include <math.h>