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PostgreSQL: Dropping Indexes (DROP INDEX)

Remove indexes from PostgreSQL tables using DROP INDEX. This guide explains when and how to drop indexes to improve database performance.

Dropping Indexes in PostgreSQL

In PostgreSQL, the `DROP INDEX` command removes an index from a table. Indexes speed up data retrieval but can slow down data modification (inserts and updates). Dropping an unused or inefficient index can improve overall database performance.

Understanding PostgreSQL Indexes

Indexes in PostgreSQL are data structures that speed up data retrieval. They're similar to the index at the back of a book—they let the database quickly locate specific rows without needing to examine every single row in the table. However, indexes add some overhead to data modification operations (inserts and updates).

`DROP INDEX` Command Syntax


DROP INDEX [CONCURRENTLY] [IF EXISTS] index_name [CASCADE | RESTRICT];

This command removes the index named `index_name`. The optional clauses are:

  • CONCURRENTLY: Drops the index concurrently with other database operations (reads and writes are allowed during the drop). This is generally preferred unless you have a specific reason to use an exclusive lock on the table. However, `CASCADE` is not allowed when using `CONCURRENTLY`.
  • IF EXISTS: Avoids errors if the index doesn't exist (results in a notice instead of an error).
  • CASCADE: Automatically removes dependent objects (like foreign key constraints referencing the index).
  • RESTRICT: (Default) Fails if the index has dependencies.

Example: Dropping an Index

(Note: This example assumes a table named `Employee` already exists with an index named `idex_emp_address`. Screenshots from the original text are not included here. Please refer to the original document for visual verification of the commands' success. The descriptions below aim to convey the information present in those screenshots.)

  1. Create Table and Index: Create an `Employee` table and an index named `idex_emp_address` on the `address` column.
  2. Verify Index: Check that the index exists using `psql` (e.g., using `\d` to list indexes).
  3. Drop the Index: Use `DROP INDEX idex_emp_address;` to drop the index.
  4. Verify Drop: Confirm the index has been removed (again using `psql`).

Dropping Multiple Indexes

You can drop multiple indexes simultaneously by listing their names separated by commas:


DROP INDEX index1, index2, index3;