How to Retrieve Indexed Columns in PostgreSQL?

Retrieve Indexed Columns in PostgreSQL

To obtain the columns indexed within PostgreSQL, you can utilize the following query:

SELECT
    t.relname AS table_name,
    i.relname AS index_name,
    a.attname AS column_name
FROM
    pg_class t,
    pg_class i,
    pg_index ix,
    pg_attribute a
WHERE
    t.oid = ix.indrelid
    AND i.oid = ix.indexrelid
    AND a.attrelid = t.oid
    AND a.attnum = ANY(ix.indkey)
    AND t.relkind = 'r';

To further aggregate the results by index, use this query:

SELECT
    t.relname AS table_name,
    i.relname AS index_name,
    array_to_string(array_agg(a.attname), ', ') AS column_names
FROM
    pg_class t,
    pg_class i,
    pg_index ix,
    pg_attribute a
WHERE
    t.oid = ix.indrelid
    AND i.oid = ix.indexrelid
    AND a.attrelid = t.oid
    AND a.attnum = ANY(ix.indkey)
    AND t.relkind = 'r'
GROUP BY
    t.relname,
    i.relname;

Additional Resources for PostgreSQL Meta-Information Extraction:

• [pg_index](https://www.postgresql.org/docs/current/static/view-pg-index.html)
• ["Extracting META information from PostgreSQL"](https://www.depesz.com/2007/08/12/extracting-meta-information-from-postgresql/)

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