I have an index named idx_1 which i want to rebuilding.
First I used the query "Select * from dba_indexes where index_name='idx_1'; ". It returned blank row. Then I gave these 2 stms "Analyze index idx_1 compute statistics; Analyze index idx_1 validate structure; ". After that I again checked the status in dba_indexes where the row was now populated. After that I gave the cmd to rebuild "Alter index idx_1 rebuild". Now when I checked the status in dba_indexes the row returned the same values before rebuilding. Why so. Who will I know that the index is rebuild.

What is the purpose of Analyze compute statistics & Analyze validate structure here.