The Distributed SQL Blog

Thoughts on distributed databases, open source and cloud native

Distributed SQL Tricks and Tips – Dec 20, 2019

VP Developer Relations

Welcome to this week’s tips and tricks blog where we recap some distributed SQL questions from around the Internet. We’ll also review upcoming events, new blogs and documentation that has been published since the last blog. Got questions? Make sure to ask them on our YugabyteDB Slack channel, Forum, GitHub or Stackoverflow. Ok, let’s dive right in:

How can I update a JSONB document in YugabyteDB?

To perform updates to JSONB you use an update statement via the YSQL API. For example:

Create a schema called store:

CREATE SCHEMA store;

Next, create a table called books:

CREATE TABLE store.books ( id int PRIMARY KEY, details jsonb );

Insert some sample JSONB documents:

INSERT INTO store.books (id, details) VALUES
(1, '{ "name": "Macbeth", "author": { "first_name": "William", "last_name": "Shakespeare" }, "year": 1623, "editors": ["John", "Elizabeth", "Jeff"] }');
INSERT INTO store.books (id, details) VALUES
(2, '{ "name": "Hamlet", "author": { "first_name": "William", "last_name": "Shakespeare" }, "year": 1603, "editors": ["Lysa", "Mark", "Robert"] }');
INSERT INTO store.books (id, details) VALUES
(3, '{ "name": "Oliver Twist", "author": { "first_name": "Charles", "last_name": "Dickens" }, "year": 1838, "genre": "novel", "editors": ["Mark", "Tony", "Britney"] }');
INSERT INTO store.books (id, details) VALUES
(4, '{ "name": "Great Expectations", "author": { "first_name": "Charles", "last_name": "Dickens" }, "year": 1950, "genre": "novel", "editors": ["Robert", "John", "Melisa"] }');
INSERT INTO store.books (id, details) VALUES
(5, '{ "name": "A Brief History of Time", "author": { "first_name": "Stephen", "last_name": "Hawking" }, "year": 1988, "genre": "science", "editors": ["Melisa", "Mark", "John"] }');

Perform a simple select to confirm you have data.

SELECT * FROM store.books;

Now, update the document which has the id set to 4:

UPDATE store.books
SET details='{"name": "Great Expectations", "year": 1950, "genre": "novel", "author": {"last_name": "Dickens", "first_name": "Jerome"}, "editors": ["Robert", "John", "Melisa"]}'
WHERE id=4;

Finally, do a select to confirm the document has been updated:

SELECT * FROM store.books WHERE id = 4;

In YugabyteDB do I need to keep string and byte objects under 64kb and 1 MB respectively in order to avoid potential performance problems?

The short answer is no, you don’t have to keep your objects below those limits. In fact, YugabyteDB’s upper limit is bound by a 32 MB RPC ceiling. Obviously, keeping columns in the 2 MB or less range will deliver better performance. But, if your use case demands it and depending on the size of the other columns, we support 32 MB sized columns.

When deploying YugabyteDB on Kubernetes, I would like to add CPU and memory request limits to my secure and insecure StatefulSet configurations. How can I go about this?

Out-of-the-box, YugabyteDB supports setting memory and CPU request limits on Kubernetes. For example:

helm install yugabyte --set resource.tserver.limits.cpu=16,resource.tserver.limits.memory=30Gi --namespace yb-demo --name yb-demo --wait

For additional information, check out the documentation on Helm Hub.

I am using yb-ctl to create a 3 node, rf=3 cluster. How can make it listen on external IP address instead of localhost?

The yb-ctl command only works for local deployments. To bring up YugabyteDB on three separate hosts, you can follow the instructions detailed in the manual deployments section of the Docs. There are a number of orchestrated multi-node deployment options available:

  • Terraform on any cloud
  • Cloud formation on AWS, Deployment manager in GCP and ARM templates in Azure
  • Kubernetes is another easy way to deploy using Operators or Helm charts.

All the available multi-host, cloud installation options are detailed at: https://download.yugabyte.com/cloud

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VP Developer Relations