topn
topn
topn : type for top-n JSONB
Overview
| ID | Extension | Package | Version | Category | License | Language |
|---|---|---|---|---|---|---|
| 4600 | topn | topn | 2.7.0 | FUNC | AGPL-3.0 | C |
| Attribute | Has Binary | Has Library | Need Load | Has DDL | Relocatable | Trusted |
|---|---|---|---|---|---|---|
--s-d-- | No | Yes | No | Yes | no | no |
| Relationships | |
|---|---|
| See Also | count_distinct quantile lower_quantile first_last_agg omnisketch ddsketch aggs_for_arrays aggs_for_vecs |
Packages
| Type | Repo | Version | PG Major Compatibility | Package Pattern | Dependencies |
|---|---|---|---|---|---|
| EXT | PGDG | 2.7.0 | 18 17 16 15 14 | topn | - |
| RPM | PGDG | 2.7.0 | 18 17 16 15 14 | topn_$v | - |
| DEB | PIGSTY | 2.7.0 | 18 17 16 15 14 | postgresql-$v-topn | - |
| Linux / PG | PG18 | PG17 | PG16 | PG15 | PG14 |
|---|---|---|---|---|---|
el8.x86_64 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 |
el8.aarch64 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 |
el9.x86_64 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 |
el9.aarch64 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 |
el10.x86_64 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 |
el10.aarch64 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 | PGDG 2.7.0 |
d12.x86_64 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 |
d12.aarch64 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 |
d13.x86_64 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 |
d13.aarch64 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 |
u22.x86_64 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 |
u22.aarch64 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 |
u24.x86_64 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 |
u24.aarch64 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 | PIGSTY 2.7.0 |
Source
pig build pkg topn; # build debInstall
Make sure PGDG repo available:
pig repo add pgdg -u # add pgdg repo and update cacheInstall this extension with pig:
pig install topn; # install via package name, for the active PG version
pig install topn -v 18; # install for PG 18
pig install topn -v 17; # install for PG 17
pig install topn -v 16; # install for PG 16
pig install topn -v 15; # install for PG 15
pig install topn -v 14; # install for PG 14Create this extension with:
CREATE EXTENSION topn;Usage
Provides approximate top-N value tracking using an approximation algorithm that keeps a predefined number of frequent items and counters. Supports materialization, incremental updates, and merging across time intervals.
CREATE EXTENSION topn;Data Type
Uses JSONB to store the frequent items and their frequencies.
Aggregates
| Function | Description |
|---|---|
topn_add_agg(text) | Aggregate that creates a JSONB counter from a text column |
topn_union_agg(jsonb) | Aggregate that merges multiple JSONB counter lists |
Functions
| Function | Description |
|---|---|
topn(jsonb, n) | Return the top-N elements and frequencies as rows |
topn_add(jsonb, text) | Add a text value to a JSONB counter |
topn_union(jsonb, jsonb) | Merge two JSONB counter lists |
Configuration
topn.number_of_counters– number of counters to track (default: 1000)
Examples
-- Materialize top products by date
CREATE TABLE popular_products (
review_date date UNIQUE,
agg_data jsonb
);
INSERT INTO popular_products
SELECT review_date, topn_add_agg(product_id)
FROM customer_reviews GROUP BY review_date;
-- Get the top-1 product for each day
SELECT review_date, (topn(agg_data, 1)).*
FROM popular_products ORDER BY review_date;
-- Top 10 across a time range (merging daily summaries)
SELECT (topn(topn_union_agg(agg_data), 10)).*
FROM popular_products
WHERE review_date >= '2000-01-01' AND review_date < '2000-02-01'
ORDER BY 2 DESC;Last updated on