Publish file sizes into both legacy and 64-bit content database columns

[rtibbles]

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Overview

Studio can now store files larger than 2.1 GB (#5974). But publish still exports only the legacy 32-bit LocalFile.file_size, which cannot represent them. This adds a 64-bit file_size_bigint column to the exported content database, populated at publish. New Kolibri (learningequality/kolibri#14881) reads the true size; old Kolibri keeps reading the legacy column. Ships with the merged included_presets change (#6004) in the same content-schema hotfix.

Complexity: Low
Target branch: hotfixes

Context

• Studio generates the content database through the vendored kolibri_content schema (base_models.py).
• create_associated_file_objects (publish.py:644) writes LocalFile rows through those models.
• The export already advertises content schema VERSION_6, set by the merged included_presets change (Publish a renderer-preset bitmask (File.included_presets) into the content database #6004).
• This issue adds file_size_bigint into that schema — no further version bump.
• MIN_SCHEMA_VERSION stays "1" (publish.py:67), so old Kolibri still imports.
• Kolibri's VERSION_6 import (Widen LocalFile.file_size to BigIntegerField for content > 2.1 GB kolibri#14881) reads LocalFile.file_size_bigint directly.
• Pre-VERSION_6 exports have their legacy file_size mapped into it instead.
• file_size_bigint is a LocalFile column only.
• Kolibri does not read a bigint size on File.
• Both the kolibri_content export mirror and the kolibri_public API mirror derive from base_models.LocalFile.

The Change

• Add a nullable file_size_bigint BigIntegerField to LocalFile in base_models.py, keeping the legacy file_size.
• Migrate both mirrors: kolibri_content/0025_* and kolibri_public/0010_*.
• In create_associated_file_objects (publish.py:661), set file_size_bigint to the real size on every LocalFile.
• Set the legacy file_size to the real size when it fits in 32 bits, else NULL.

Out of Scope

• A bigint size on the File model — Kolibri reads size from LocalFile only.
• Widening Studio's own File.file_size storage column (Widen File.file_size to 64-bit (bigint) via zero-downtime expand/contract #5974, done).
• The channel published_size aggregate (publish.py:936).
• Resumable upload changes.

Acceptance Criteria

General

• LocalFile in the export models carries a nullable file_size_bigint alongside the legacy file_size.
• Both the kolibri_content and kolibri_public mirrors migrate the new column.
• A channel with a >2.1 GB file imports into current Kolibri with the full size, and into pre-VERSION_6 Kolibri with NULL for that file's size.

Testing

• Publishing a file ≤2.1 GB writes the same value to file_size and file_size_bigint.
• Publishing a file >2.1 GB writes the real value to file_size_bigint and NULL to file_size.
• The exported database imports into current Kolibri with the full size populated.

References

• contentcuration/contentcuration/utils/publish.py — create_associated_file_objects, MIN_SCHEMA_VERSION
• contentcuration/kolibri_content/base_models.py — LocalFile
• Widen LocalFile.file_size to BigIntegerField for content > 2.1 GB kolibri#14881 — Kolibri LocalFile.file_size_bigint counterpart
• Widen File.file_size to 64-bit (bigint) via zero-downtime expand/contract #5974 — Studio-side bigint storage (done)
• Publish a renderer-preset bitmask (File.included_presets) into the content database #6004 — sibling content-schema change (included_presets)

AI usage

I used Claude (Opus 4.8, via le-skills:writing-github-issues) to draft this issue against the merged included_presets export (#6004) and the Kolibri counterpart (#14881). The design was mine; Claude mapped the code and wrote it up.

[rtibblesbot]

Plan: Export a 64-bit file_size_bigint on LocalFile at publish so channels with >2.1 GB files carry their true size into new Kolibri, while old Kolibri keeps reading the legacy 32-bit file_size.

• Schema — file_size_bigint field + both mirror migrations
• Populate file_size_bigint and clamp legacy file_size at publish

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@rtibblesbot's comments are generated by an LLM, and should be evaluated accordingly

How was this generated?

• Implemented code following the pre-approved plan using test-driven development (red-green-refactor)
• Ran the project's full test suite and linter before committing
• For UI changes: captured live screenshots to verify rendering
• For backend changes: verified with example API/CLI output

[rtibbles]

Fixed in #6041