Too wide composite indexes

Query goal:

Find composite indexes that do not support any constraint but are on more than three columns.

Notes about the query:

The query does not count any included columns, which are merely stored and do not participate in the index semantics. According to the PostgreSQL documentation: "Multicolumn indexes should be used sparingly. In most situations, an index on a single column is sufficient and saves space and time. Indexes with more than three columns are unlikely to be helpful unless the usage of the table is extremely stylized."

Query type:

Problem detection (Each row in the result could represent a flaw in the design)

Query reliability:

Low (Many false-positive results)

Query license:

MIT License

Data source:

system catalog only

SQL query:

Click on query to copy it

SELECT pg_get_indexdef(indexrelid) AS indexdef, indnkeyatts AS number_of_columns, n.nspname AS table_schema, c.relname AS table_name
FROM pg_index AS i INNER JOIN pg_class AS c ON i.indrelid=c.oid
INNER JOIN pg_namespace AS n ON n.oid=c.relnamespace
INNER JOIN pg_authid AS a ON n.nspowner=a.oid
WHERE (n.nspname='public' OR a.rolname<>'postgres')
AND indnkeyatts >3
AND NOT EXISTS (SELECT *
FROM pg_constraint
WHERE i.indexrelid=pg_constraint.conindid)
ORDER BY indnkeyatts DESC, table_schema, table_name;

Collections where the query belongs to

Collection name	Collection description
Find problems automatically	Queries, that results point to problems in the database. Each query in the collection produces an initial assessment. However, a human reviewer has the final say as to whether there is a problem or not .

Collection name

Collection description

Find problems automatically

Queries, that results point to problems in the database. Each query in the collection produces an initial assessment. However, a human reviewer has the final say as to whether there is a problem or not .

Categories where the query belongs to

Category name	Category description
Performance	Queries of this category provide information about indexes in a database.

Category name

Category description

Performance

Queries of this category provide information about indexes in a database.

Reference materials for further reading

Reference
https://www.postgresql.org/docs/current/indexes-multicolumn.html

Reference

https://www.postgresql.org/docs/current/indexes-multicolumn.html