Description:
The Merge node in SQL Query mode intermittently returns “No output data returned” and halts the workflow, despite identical inputs and logic that worked reliably until recently.
Key observations:
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All upstream nodes execute successfully
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Inputs still contain data
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The SQL query executes without error
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The node returns zero rows, even though it previously returned valid results with the same logic
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Removing the where clause or simplifying joins sometimes produces output, suggesting a behavior change rather than a query syntax issue
Expected behavior:
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Input data shape is unchanged
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Join keys are present
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Filters match existing rows
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Behavior should be consistent across versions or documented if changed
Actual behavior:
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Merge node outputs no data
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Workflow stops execution
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No warnings or errors indicating why rows were filtered out
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Same data and logic previously worked
