PrestoDB Questions & Answers

Creating tables in a S3 Bucket gives “Query failed External location must be a directory” So here’s why you are here. You are using Presto’s Hive connector and you want … Continue reading Creating Tables In A S3 Bucket Issues | Ahana

Big Data Query When it comes to querying big data using standard SQL you have come to the right place as this is what Presto was designed to do. Presto, … Continue reading Big Data Query | Presto Big Data | Ahana

I use RDS Postgres databases and need some complex queries done which tend to slow down my databases for everyone else on the system. What do I need to consider … Continue reading RDS Postgres Databases Complex Queries | Ahana

Advanced SQL Tutorial JSON Presto has a wide-range of JSON functions. Consider this json test input data (represented in the query using the  VALUES function) which contains 3 key/value elements. … Continue reading Advanced SQL Tutorial & SQL Queries Support

Complex SQL Queries Complex SQL queries benefit from Presto’s distributed, parallel, in-memory processing architecture and cost-based optimizer. And with Presto’s federation capabilities even more complex queries can be unleashed on … Continue reading Complex SQL Queries | SQL Complex Queries | Ahana

Advanced SQL Queries with Presto Advanced SQL features and functions are used by analysts when, for example, complex calculations are needed, or when many tables (perhaps from multiple sources) need … Continue reading Advanced SQL Queries with Presto | SQL Queries Presto | Ahana

Presto Platform Overview Presto is an open source distributed SQL query engine for running interactive analytic queries against data sources of all sizes. Some of the world’s most innovative and … Continue reading Presto Platform Overview: Interactive Analytic Queries

How To Stop Presto If you are using the presto-admin tool this is how to stop Presto safely: $ presto-admin server stop In addition these commands are also useful: presto-admin … Continue reading How to Stop Presto Tutorial | EMR Restart Presto Tutorial | Ahana

Presto New Releases Where is the latest release of PrestoDB? And where can I find the release notes? Where is the documentation? These are common questions with easy answers. Presto’s … Continue reading Presto New Releases & Latest Release

How Much Memory To Give A Presto Worker Node Presto is an in-memory query engine and so naturally memory configuration and management is important. A common question that comes up is … Continue reading How Much Memory To Give A Presto Worker Node | Presto Memory | Ahana

How to Show Tables From All Schemas with Presto In Presto it is straightforward to show all tables in a schema e.g. If we have a MySQL data source/catalog that … Continue reading Show Tables From Schemas With Presto | Presto Information_Shema | Ahana

How To Convert Bigint to Timestamp with Presto UNIX timestamps are normally stored as doubles. If you have UNIX timestamps stored as big integers then you may encounter errors when … Continue reading Convert Presto Bigint To Timestamp | Bigint To Timestamp Presto | Ahana

How do I convert timestamp to date with Presto? Luckily Presto has a wide range of conversion functions and they are listed in the docs.  Many of these allow us … Continue reading Convert Timestamp To Date With Presto | Ahana

Case Sensitive Search Configuration with Presto When dealing with character data, case sensitivity can be important when  searching for specific matches or patterns. But not all databases and query engines … Continue reading Case Sensitive Search Configuration with Presto | Presto Regex | Ahana

When should I use ORC versus Parquet when using Presto? If you’re working with open data lakes using open source and open formats, you can have multiple formats. Presto works … Continue reading Use ORC Versus Parquet When Using Presto | Ahana

What’s the advantage of having your own Hive metastore with Presto? How does it compare to Amazon Glue? First let’s define what Apache Hive is versus Amazon Glue. Apache Hive … Continue reading Benefits Of Hive Metastore With Presto | Ahana

How to Find Out Data Type of Value with Presto Presto has a typeof() function to make finding out data types of values easy. This is particularly useful when you … Continue reading Find Out Data Type of Value with Presto | Presto Check Data Type | Ahana

How to Rotate Rows to Columns with Presto Sometimes called pivoting, here is one example of how to switch columns to rows via rotation with Presto.   Suppose we have rows … Continue reading Presto Pivot Rows to Columns | Rows to Columns via Rotation | Ahana

Sometimes called unpivoting, here is one example of how to rotate column data with Presto.   Suppose we have some integer data arranged in two columns called a and b: a … Continue reading How do you rotate columns to rows with Presto?

What are the operational benefits of using a managed service for Presto with Ahana Cloud? First let’s hear from an AWS Solution Architect: “Ahana Cloud uses the best practices of … Continue reading Benefits Of Using Managed Service For Presto | Ahana

How to Lateral View Explode in Presto Hive’s explode() function takes an array (or a map) as input and outputs the elements of the array (map) as separate rows. Explode … Continue reading Presto Explode Array | Lateral View Explode in Presto | Ahana

Let’s take a look at how you can cross join unnest a JSON array by doing Presto joins. Here’s an example using test results data in json form as input, … Continue reading How do you cross join unnest a JSON array?

With Ahana Cloud, we’ve made it easy for you write output of queries to S3. While there’s a variety of formats, here’s an example:

With Amazon Athena you’re limited in scope when it comes to doing joins across other data sources like relational data systems and more. You have to set up a Lambda, … Continue reading Does Amazon Athena do joins across other data sources besides S3? Does Amazon Athena connect to other data sources?

If you’re managing Presto on your own, either through your own installation or through a service like AWS EMR or AWS Athena, you have to maintain and manage all of … Continue reading If I have catalogs connected and configurations attached to my Presto cluster, what happens when I take the cluster down?

Check If Map Or Presto Array Is Empty Or Contains When working with array (indexable lists) or map (key-value tuple) complex types in Presto, it is useful to be able … Continue reading Presto Map | Check If Map Or Presto Array Is Empty Or Contains | Ahana

Export Result Of Select Statement in Presto A common question is “how can I run a query and export result of select statement quickly and easily in Presto?”  You are … Continue reading Export Result Of Select Statement in Presto | Presto Export to CSV | Ahana

How to Manage Presto Queries Running Slow There are a few reasons that Presto performance is impacted and queries might be running slow. Below we’ll share some things to do … Continue reading Presto Queries Running Slow | Slow Queries & Presto Tuning | Ahana

Extract Keys in a Nested JSON Array Object With Presto Let’s say we have some JSON that looks like this: In this instance our json contains key value pairs. How … Continue reading Presto JSON | Extract Keys In A Nested JSON Array Object | Ahana

Generate Interval from Variable Using PrestoDB There are numerous ways to generate interval from variable using PrestoDB SQL for different data types. Dates Date intervals can be generated for a … Continue reading Generate Interval from Variable Using PrestoDB | Ahana

How to Presto Escape a Single Quote In reality there will be some occasions when you need to use a quote character in your data, in your query, or in … Continue reading How To Presto Escape Single Quote | Presto Escape Quote | Ahana

Check if null and return default (NVL analog) SQL has a number of functions for dealing with null values, and everyone has their favorite. The complicating factor is that not … Continue reading Check If Null & Return Default (NVL analog) | Ahana

Static date and timestamp in where clause In this post we’ll look at the static date and timestamp in where clause when it comes to Presto. Many databases automatically convert … Continue reading Static Date & Timestamp In Where Clause | PrestoDB Timestamp

Where can I find the Presto Server Bootstrap logs? A common question is “where can I find the Presto server bootstrap logs?”  These are logs that indicate what is happening … Continue reading Where Can I Find The Presto Server Bootstrap Logs | Ahana

Where can I find different Presto metrics for monitoring? If you’re wondering “Where can I find different Presto metrics for monitoring?”, we’ll help explain it. There are several ways to … Continue reading Where Can I Find Different Presto Metrics For Monitoring | Ahana

Where to Find Presto Logs If you’re wondering “where do I find Presto logs”, we’ll help explain it. Presto needs a data directory for storing logs, etc. and it is … Continue reading Where To Find Presto Logs | Presto Logs EMR | Ahana

Presto equivalent of mysql group_concat PrestoDB supports ANSI SQL and includes support for several SQL dialects, including MySQL dialect, making it easy to group and aggregate data in a variety … Continue reading Presto Equivalent Of mysql group_concat | group_concat Presto

How to Get the Presto CLI Tool The Presto CLI provides a terminal-based interactive shell for running queries. The CLI is a self-executing JAR file, which means it acts like … Continue reading Presto CLI Download | How to Get the Presto CLI Tool | Ahana

How To Convert Date String to Presto Date Format PrestoDB supports ANSI SQL and includes support for several SQL dialects, so it’s straightforward to convert a date string to date … Continue reading Convert Date String to Date Format in Presto | Presto Date Function | Ahana

Where to Find Presto Source Code & How to Work With It The main branch: PrestoDB source code Presto is an open source project that is developed in the open … Continue reading Where to Find Presto Source Code | PrestoDB Source Code GitHub | Ahana