pg_index #
   The catalog pg_index contains part of the information
   about indexes.  The rest is mostly in
   pg_class.
  
Table 51.26. 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 | 
| 
        This value is only used for unique indexes. If false, this unique index will consider null values distinct (so the index can contain multiple null values in a column, the default PostgreSQL behavior). If it is true, it will consider null values to be equal (so the index can only contain one null value in a column). | 
| 
        
       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  |