trinodb/trino

Return execution metrics while running the `OPTIMIZE` command in Delta Lake

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#28999 opened on Apr 6, 2026

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 (3 comments) (1 reaction) (0 assignees)Java (9,113 stars) (2,678 forks)batch import
delta-lakegood first issue

Description

We can return metrics such as rewritten data files, removed deletion vectors, added data files in Delta Lake OPTIMIZE procedure.

https://github.com/trinodb/trino/blob/11bf3c068037352ed9ee6fb8293154c7b9416452/plugin/trino-delta-lake/src/main/java/io/trino/plugin/deltalake/DeltaLakeMetadata.java#L2940-L2950

Contributor guide

Tech stack
java
Domain
databaseperformance
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Java programmingUnderstanding of Delta Lake OPTIMIZE
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
Examine the referenced file DeltaLakeMetadata.java around line 2940 for the current OPTIMIZE implementation. Review the follow up PR #28992 to understand the expected pattern for returning metrics. Implement changes to collect and return metrics such as rewritten data files, removed deletion vectors, and added data files after the OPTIMIZE procedure.