# Read support for original files of Hive transactional tables in Presto

DevFeed: [Read support for original files of Hive transactional tables in Presto](<https://devfeed.tech/articles/read-support-for-original-files-of-hive-transactional-tables-in-presto-8650.md>)

Original publisher: [Read original article](<https://trino.io/blog/2020/09/23/hive-acid-original-files.html>)

Author: Harmandeep Singh, Qubole

Published: 2020-09-23T00:00:00Z

Content type: article

Language: en

Sources: [Trino Blog](<https://devfeed.tech/sources/trino-blog.md>)

Topics: [data](<https://devfeed.tech/topics/data.md>)

Tags: [blog](<https://devfeed.tech/tags/blog.md>), [support](<https://devfeed.tech/tags/support.md>)

## AI overview

This article explains how Presto 340 added read support for original files in Hive transactional tables. It describes why tables converted from non-ACID format could previously fail to read and how synthetic ACID columns support updates and deletes on those original files.

## Source excerpt

In Presto 331, read support for Hive transactional tables was introduced. It works well, if a user creates a new Hive transactional table and reads it from Presto. However, if an existing table is converted to a Hive transactional table, Presto would fail to read data from such a table because read support for original files was missing. Original files are those files in a Hive transactional table that existed before the table was converted into a Hive transactional table. Until version 340, Presto expected all files in a Hive transactional table to be in Hive ACID format. Users would have to perform a major compaction to convert original files into ACID files (i.e. base files) in such tables. This is not always possible as the original flat table (table in non-ACID format) could be huge and converting all the existing data into ACID format can be very expensive. This blog is an extension of the blog Hive ACID and transactional tables' support in Presto. It first describes original files and then goes into details of read support for such files that was added in Presto 340.