apache/iceberg

Spark: Fix map value decoding in test helpers for older versions

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#17,717 opened on Aug 19, 2026

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good first issuespark

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Description

Problem

The map comparison helpers decode both keys and values with the map key type:

Object actualKey = actualKeys.get(i, convert(keyType));
Object actualValue = actualValues.get(i, convert(keyType));

The value must be decoded with convert(valueType). When the key and value types differ, the current assertions may decode the value incorrectly and do not validate what they appear to validate.

PR #14984 fixes GenericsHelpers for Spark 4.2 and will also fix the duplicate in Spark 4.2 TestHelpers. The same issue remains in both helpers for:

  • spark/v3.5
  • spark/v4.0
  • spark/v4.1

Proposed fix

Update the remaining six occurrences to use:

Object actualValue = actualValues.get(i, convert(valueType));

Add or confirm coverage using a map whose key and value have different Spark types.

Context

Identified while reviewing Spark 4.2 support in #14984: https://github.com/apache/iceberg/pull/14984#discussion_r3788259735

Contributor guide

Research direction
Inspect the map comparison helpers in the spark/v3.5, spark/v4.0, and spark/v4.1 directories. Locate the six lines where both keys and values are decoded with convert(keyType) and change the value lines to use convert(valueType). Add a test with a map whose key and value have different Spark types to ensure correct behavior.
Tech stack
java
Domain
backendtesting
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitJava
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80