pg_index
   The catalog pg_index contains part of the information
   about indexes.  The rest is mostly in
   pg_class.
  
Table 53.26. pg_index Columns
Column Type Description  | 
|---|
        
       The OID of the   | 
        
       The OID of the   | 
        
       The total number of columns in the index (duplicates
         | 
        The number of key columns in the index, not counting any included columns, which are merely stored and do not participate in the index semantics  | 
        If true, this is a unique index  | 
        
       If true, this index represents the primary key of the table
       (  | 
        If true, this index supports an exclusion constraint  | 
        
       If true, the uniqueness check is enforced immediately on
       insertion
       (irrelevant if   | 
        If true, the table was last clustered on this index  | 
        
       If true, the index is currently valid for queries.  False means the
       index is possibly incomplete: it must still be modified by
         | 
        
       If true, queries must not use the index until the   | 
        
       If true, the index is currently ready for inserts.  False means the
       index must be ignored by   | 
        If false, the index is in process of being dropped, and should be ignored for all purposes (including HOT-safety decisions)  | 
        
       If true this index has been chosen as “replica identity”
       using   | 
        
       This is an array of   | 
        
       For each column in the index key
       (  | 
        
       For each column in the index key
       (  | 
        
       This is an array of   | 
        
       Expression trees (in   | 
        
       Expression tree (in   |