[processor/metricstransform] Fix silent data loss for single Summary metric in combine action

[himanshu130700]

fixes #49693

Documentation

Authorship

• I, a human, wrote this pull request description myself.

[opentelemetry-pr-dashboard]

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Merged · refreshed 2026-08-05 11:32 UTC

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[Copilot]

Pull request overview

Fixes a metrics transform processor edge case where combine on a single matched Summary metric could silently drop all Summary datapoints, by ensuring Summary metrics are rejected before the len(metrics) <= 1 early-return.

Changes:

• Update canBeCombined to always guard against Summary metrics (including the single-match case).
• Add a regression test covering combine + single Summary match to ensure the metric passes through unchanged.
• Add a user-facing changelog entry describing the behavioral fix.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
processor/metricstransformprocessor/metrics_transform_processor_otlp.go	Moves the Summary-type guard ahead of the len <= 1 early exit to prevent combine from proceeding for Summary metrics.
processor/metricstransformprocessor/metrics_transform_processor_testcases_test.go	Adds a regression test ensuring a single matched Summary metric is not combined/dropped.
.chloggen/49693-metricstransform-combine-summary-single.yaml	Adds a changelog entry documenting the fix for silent Summary datapoint loss.

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