P: Unknown Error while importing a catalog into an existing catalog
Lightroom Classic Version: 15.5
Operating System: macOS Tahoe 26.6.2 (25G83)
Steps to reproduce:
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Open a primary Lightroom Classic catalog.
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Go to File > Import from Another Catalog.
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Select a large secondary catalog (e.g., 16,000+ or 43,000+ images).
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Start the import process.
Expected result: The catalog import should process all images and complete successfully.
Actual result: The import process fails midway with a generic "An unknown error occurred" dialog box.
Key Pattern Identified: The import process stops at exact, round batch numbers:
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On a catalog containing 16,623 images, the import halted at exactly 15,000 images.
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On a catalog containing 43,881 images, the import halted at exactly 25,000 images.
Additional Diagnostic Details:
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Telemetry log right before crash:
last_command = "ag.file.import.fromlibrary" -
RAM usage remains low (under 3 GB / ~8% memory total), ruling out memory saturation.
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The exact round numbers (15k / 25k) strongly suggest a batch transaction commit failure or an index buffer overflow during the SQLite database merge process.
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