How to get table index size in PostgreSQL

Software Engineer

2024-07-10 23:01:49 +0700 · 2 mins read

Indexes play a crucial role in enhancing the performance of database queries. They allow for faster data retrieval by creating a separate data structure pointing to the data stored in a table. However, indexes come with a cost in terms of disk space consumption. Understanding the size of indexes helps you evaluate their impact on storage requirements and overall database performance. In this blog post, we will explore how to get the table index size in PostgreSQL

1. Index size of all tables

To retrieve the index size of all tables in PostgreSQL

// language: sql
SELECT
    relname AS object_name,
    pg_size_pretty(pg_relation_size(relid)) AS table_size,
    pg_size_pretty(pg_indexes_size(relid)) AS index_size,
    pg_size_pretty(pg_total_relation_size(relid)) AS total_size
FROM pg_catalog.pg_statio_user_tables
ORDER BY pg_total_relation_size(relid) DESC;

The sample result is

// language: bash
"object_name"    "table_size"    "index_size"   "total_size"
"users"          "8192 bytes"    "64 kB"        "80 kB"
"admin_users"    "8192 bytes"    "48 kB"        "64 kB"

2. Index type of each table

To retrieve each index type in the table "users" (you can try with other tables)

// language: sql
SELECT i.relname "Table Name",indexrelname "Index Name",
 pg_size_pretty(pg_total_relation_size(relid)) As "Total Size",
 pg_size_pretty(pg_indexes_size(relid)) as "Total Size of all Indexes",
 pg_size_pretty(pg_relation_size(relid)) as "Table Size",
 pg_size_pretty(pg_relation_size(indexrelid)) "Index Size"
FROM pg_stat_all_indexes i JOIN pg_class c ON i.relid=c.oid 
WHERE i.relname='users'

The sample result is

// language: bash
"Table Name"   "Index Name"                             "Total Size"    "Total Size of all Indexes"    "Table Size"    "Index Size"
"users"        "users_pkey"                             "80 kB"         "64 kB"                        "8192 bytes"    "16 kB"
"users"        "index_users_on_email"                   "80 kB"         "64 kB"                        "8192 bytes"    "16 kB"
"users"        "index_users_on_reset_password_token"    "80 kB"         "64 kB"                        "8192 bytes"    "16 kB"
"users"        "index_users_on_confirmation_token"      "80 kB"         "64 kB"                        "8192 bytes"    "16 kB"

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