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PostgreSQL Update HStore field | Guide

In PostgreSQL, the HStore data type is a helpful tool that manages dynamic key-value pairs within a single column.

Today, we are going to take a close look at HStore.

Before we begin, make sure the HStore extension is enabled in your PostgreSQL database. If not already enabled, run this command:

CREATE EXTENSION hstore;

How to Create Tables with HStore Fields

Once the extension is in place, we can easily create tables with HStore fields effortlessly.
It involves defining the field as an HStore type during table creation as seen here:

CREATE TABLE products (
id serial primary key,
title VARCHAR (255),
attr hstore
);


When dealing with PostgreSQL’s HStore fields, you may have multiple values or attributes in one field. This means updating them requires more flexibility. In some case cases we may want to update just parts of it. Thankfully, PostgreSQL provides operators and options to help you manage your HStore data effectively.

How to Manipulate HStore Data

• Adding Key-Value Pairs

  We can use the `||` operator to add another key-value pair to an existing hstore field in Postgres. We also need to use the :: operator to convert the result into an hstore type.
• Updating Existing Key-Value Pairs

  We can easily update an existing key-value pair by just using the existing key. As a result, the old value will be replaced by the new one automatically.

  Furthermore, PL/pgSQL cannot detect variables within a string literal. So, we need to use the “constructor” method of the hstore type as seen here:

  
UPDATE products
SET attr = attr || hstore('new_key', 'new_value')
WHERE id = desired_id;


Now, suppose we want to cast a variable defined as a number to a text value. In this case, we can follow this example:

UPDATE files
SET details = hstore('new_users', new_user_count::text)
where id = v_file_id;


Furthermore, we can do this for multiple variables by:

• Concatenating two hstore values:

  details = hstore('new_users', new_user_count::text)||hstore('post_count', c_post_count::text)
• Using arrays:

  details = hstore(array['new_users','post_count'], array[c_user_count, c_post_count]::text[]);


However, if we want to replace only new_users in the HStore:

UPDATE files
SET details = details || hstore('new_users', c_new_user_count::text)
where id = v_file_id;


Alternatively, we can use this:

UPDATE tab SET h = h || ARRAY['b => 2'::hstore,'c => 3'::hstore];

This will replace new_users if it is already present in the column or add a new entry.

Let us know in the comments if you need further help with updating an hstore field in PostgreSQL

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Conclusion

In brief, our Support Experts demonstrated how to update HStore field in PostgreSQL.