How to Quickly Enumerate Indexes in Oracle 11gR2

Do you want to know real quick what kind of indexes there are on any given table in your Oracle schema? Nothing simpler than that. Just run the following query:

SELECT
  i.index_name,
  listagg(c.column_name, ', ') 
    WITHIN GROUP (ORDER BY c.column_position)
    AS columns
FROM all_indexes i
JOIN all_ind_columns c 
  ON i.index_name = c.index_name
WHERE i.table_name = 'FILM_ACTOR'
GROUP BY i.index_name

The above query is ran against the Sakila database. Just replace the “FILM_ACTOR” table by your table and you’re all set. The result looks like:

INDEX_NAME                COLUMNS
-------------------------------------------
IDX_FK_FILM_ACTOR_ACTOR   ACTOR_ID
IDX_FK_FILM_ACTOR_FILM    FILM_ID
SYS_C007155               ACTOR_ID, FILM_ID

Sometimes, it’s the simple things…

Explanation about LISTAGG

LISTAGG is a so-called ordered-set aggregate function, added in 11gR2, i.e. the aggregate function will aggregate the data “WITHIN a GROUP” given a specific “ORDER”. This is obviously useful for string concatenation, but it can be very useful also for a variety of other functions, such as inverse distribution functions, such as the MEDIAN, which we’ve blogged about here.

The syntax is:

function(...) WITHIN GROUP (ORDER BY ...)

Oracle Tip: v$sql Table or View does not Exist

If we want to analyse execution plans on the SQL console, we probably need to find a SQL_ID first, which we can the pass to the DBMS_XPLAN.DISPLAY_CURSOR function. One way to find this SQL_ID is by querying the v$sql table first, e.g.:

SELECT   last_active_time, 
         sql_id, 
         child_number, 
         sql_text
FROM     v$sql
WHERE    upper(sql_fulltext) LIKE '%SOME_SQL_TEXT%'
ORDER BY last_active_time DESC;

Now, often, you will then get an error message like:

ORA-00942: table or view does not exist

This simply means that you do not have the required privileges to select from that table. Have your DBA give you the required grant, or do it yourself on your local Oracle instance with:

C:\> sqlplus "/ as sysdba"

SQL> GRANT SELECT ANY DICTIONARY TO MY_USER;

Grant succeeded

Done. You can now query v$sql

More details about how to analyse execution plans on the SQL console can be seen here.