Information_schema on Postgres Scripts

List PostgreSQL Partitioned Tables with SQL

Thu, 09 Apr 2026 00:00:00 +0000

How to List PostgreSQL Partitioned Tables

PostgreSQL table partitioning splits a large table into smaller physical pieces called child partitions. This improves query performance and simplifies data lifecycle management. But as a DBA, you need a quick way to see which tables in your database use partitioning — and which do not.

This SQL query reads directly from the PostgreSQL system catalogs to list every table in your database, labeling each as a partitioned table or an ordinary table, while excluding system schemas and child partition tables.

Find PostgreSQL Tables Without a Primary Key

Wed, 08 Apr 2026 00:00:00 +0000

How to Find PostgreSQL Tables Without a Primary Key

A missing primary key is one of the most common and damaging database design oversights. Without a primary key, PostgreSQL has no reliable way to uniquely identify a row. This causes problems with logical replication, ORM frameworks, and application-level updates or deletes that may silently affect the wrong rows.

This SQL query scans information_schema to find every user table in your database that has no primary key or unique key constraint. Running it regularly is a simple way to catch schema problems before they reach production.

List All Views in a PostgreSQL Database with SQL

Tue, 07 Apr 2026 00:00:00 +0000

How to List All Views in a PostgreSQL Database

Views are saved SQL queries stored in the database. A production database can accumulate dozens or hundreds of views over time — many created by developers, some by tools, and some that are no longer used. Knowing what views exist, which schema they belong to, and what they actually do is essential for documentation, auditing, and cleanup.

This SQL script queries information_schema.views to return every view in the current database, along with its schema and full SQL definition.

List PostgreSQL Enum Types and Their Values with SQL

Mon, 06 Apr 2026 00:00:00 +0000

How to List All Enum Types in a PostgreSQL Database

PostgreSQL supports user-defined enum types — a fixed ordered set of string values stored efficiently as integers. Enums are common in application schemas for columns like status, role, or priority. Once created, their allowed values are managed in the database catalog, not in application code.

Over time, a database can accumulate many enum types, some with values that no longer match what the application uses. This SQL script queries pg_type and pg_enum to list every enum type in the current database along with all of its allowed values.

List Foreign Key Constraints in PostgreSQL

Sun, 05 Apr 2026 00:00:00 +0000

List Foreign Key Constraints in PostgreSQL

Foreign key constraints enforce referential integrity between tables. They guarantee that a value in one table's column always has a matching row in another table. Knowing which foreign keys exist — and how they are defined — is essential before dropping tables, renaming columns, or loading large datasets.

This SQL query lists every foreign key in the public schema, showing the table that owns the constraint, the constraint name, and the full constraint definition including which columns it spans and which table it references.

List PostgreSQL Object Comments with SQL

Sat, 04 Apr 2026 00:00:00 +0000

List PostgreSQL Object Comments with SQL

PostgreSQL allows you to attach plain-text comments to tables, columns, indexes, functions, and other database objects using the COMMENT ON command. These comments are stored in the system catalog and are visible in psql, pgAdmin, and any tool that reads pg_description. They are one of the most underused features for keeping a schema self-documenting.

This SQL query lists comments on every column across all tables in your database, showing the schema, table name, column name, and the comment text. It is useful for auditing schema documentation, onboarding new team members, and verifying that comments are in place before a schema handover.

Detect Soft Delete Patterns in PostgreSQL

Fri, 03 Apr 2026 00:00:00 +0000

Detecting Soft Delete Patterns in PostgreSQL

Soft deletes are a common application pattern. Instead of removing a row with a DELETE statement, the application marks it as deleted by setting a column — typically deleted_at — to a non-null timestamp. The row stays in the table forever. The application simply filters it out with a WHERE deleted_at IS NULL clause.

This pattern is useful for audit trails, undo functionality, and referential integrity. It is also a significant source of problems for PostgreSQL DBAs who do not know it is in use.

List PostgreSQL Tables by Size with SQL

Sun, 15 Mar 2026 00:00:00 +0000

List PostgreSQL Tables by Size with SQL

This PostgreSQL query lists all tables in the current database sorted by their total size, largest first. It uses pg_total_relation_size() to include the table data, indexes, TOAST storage, and free space map in the size calculation.

Purpose and Overview

Disk space pressure is a common operational concern in any growing database. Knowing which tables consume the most space allows administrators to prioritise archiving, partitioning, or compression efforts. It also helps explain sudden disk growth when a particular table has expanded unexpectedly.

PostgreSQL Table Row Count Estimates with SQL

Sat, 14 Mar 2026 00:00:00 +0000

PostgreSQL Table Row Count Estimates with SQL

This PostgreSQL query returns estimated row counts for all user tables, sorted by the largest tables first. It reads from the statistics collector rather than scanning the tables, making it near-instant even on tables with billions of rows.

Purpose and Overview

Counting rows with SELECT COUNT(*) FROM table requires a full sequential scan of the table — on large tables this can run for minutes and generate significant I/O load. PostgreSQL's statistics collector maintains a continuously updated row estimate for every table in pg_stat_user_tables. This estimate is fast to read and accurate enough for most operational purposes.

Identify Underutilized PostgreSQL Columns for Optimization

Wed, 03 Apr 2024 00:00:00 +0000

Identifying Underutilized Columns in Your PostgreSQL Database

Keeping your PostgreSQL database clean and efficient is crucial for optimal performance. One way to achieve this is by identifying and potentially removing "useless" columns – those that hold minimal or redundant data. This article explores a PostgreSQL code snippet designed to unearth such columns, helping you optimize your database schema.

Sample Code from Command Line

 1SELECT
 2 nspname,
 3 relname,
 4 attname,
 5 typname,
 6 (stanullfrac*100)::int AS null_percent,
 7 case
 8 when stadistinct >= 0
 9 then stadistinct
10 else
11 abs(stadistinct)*reltuples
12 end AS "distinct",
13 case 1
14 when stakind1
15 then stavalues1
16 when stakind2
17 then stavalues2
18 end AS "values"
19FROM
20 pg_class c
21JOIN
22 pg_namespace ns
23ON
24 (ns.oid=relnamespace)
25JOIN
26 pg_attribute
27ON
28 (c.oid=attrelid)
29JOIN
30 pg_type t
31ON
32 (t.oid=atttypid)
33JOIN
34 pg_statistic
35ON
36 (c.oid=starelid AND staattnum=attnum)
37WHERE
38 nspname NOT LIKE E'pg\\_%'
39 AND
40 nspname != 'information_schema'
41 AND
42 relkind = 'r'
43 AND
44 NOT attisdropped
45 AND
46 attstattarget != 0
47 AND
48 reltuples >= 100
49 AND
50 stadistinct BETWEEN 0 AND 1
51ORDER BY
52 nspname,
53 relname,
54 attname;

Notes: Finds useless PostgreSQL columns containing only a single value eg. all NULLs or a redundant non-distinguishing field. Only returns columns with over 100 rows. Tested on PostgreSQL 8.4, 9.x, 10.x, 11.x, 12.x, 13.0

PostgreSQL query to find columns containing only NULL values

Sun, 24 Mar 2024 00:00:00 +0000

Identifying Null-Only Columns in PostgreSQL

This article explores a valuable PostgreSQL query for database administrators. It helps identify columns within your database tables that exclusively contain NULL values. Uncovering these "null-only" columns can be a key step in optimizing storage usage and streamlining your database schema design.

Sample Code from Command Line

 1SELECT
 2 nspname,
 3 relname,
 4 attname,
 5 typname,
 6 (
 7 stanullfrac*100
 8 )
 9 ::int AS null_percent
10FROM
11 pg_class c
12 JOIN
13 pg_namespace ns
14 ON (ns.oid = relnamespace)
15 JOIN
16 pg_attribute
17 ON (c.oid = attrelid)
18 JOIN
19 pg_type t
20 ON (t.oid = atttypid)
21 JOIN
22 pg_statistic
23 ON (c.oid = starelid
24 AND staattnum = attnum)
25WHERE
26 (
27 stanullfrac*100
28 )
29 ::int = 100
30 AND nspname NOT LIKE E'pg\\_%'
31 AND nspname != 'information_schema'
32 AND relkind = 'r'
33 AND NOT attisdropped
34 AND attstattarget != 0 -- AND
35 --reltuples >= 100
36ORDER BY
37 nspname,
38 relname,
39 attname;

Notes: Finds PostgreSQL columns that contain only NULLs. Tested on PostgreSQL 8.4, 9.x, 10.x, 11.x, 12.x, 13.0.