57 lines
2.9 KiB
SQL
57 lines
2.9 KiB
SQL
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-- Put the output format inside `variant`, where the plan says new axes go.
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--
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-- `content_derived_blobs.variant` held the size alone (`icon` | `preview` |
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-- `large`), so a size could hold exactly ONE stored artifact regardless of
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-- codec. That surfaced when the read order flipped (step 10c): a JPEG request
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-- matched the WebP row and would have been served the wrong codec, which the
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-- old ordering hid because the `.jpg` sidecar won first. The flip had to be
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-- gated to WebP, which in turn means JPEG clients can never leave the sidecar
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-- — so the sidecar can never be deleted.
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--
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-- It blocks transcodes harder still: those are multi-format by nature, so
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-- without a format term two output codecs of one source collide on the
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-- primary key.
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--
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-- Per the column's own comment — "new axes go inside this string, never into
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-- new columns" — the axis goes in the string rather than into a fourth PK
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-- column. The PK stays `(source_hash, kind, variant)`.
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--
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-- Shape: `{size}.{ext}` — `preview.webp`, `icon.jpg`, and later `720p.webp`
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-- for transcodes.
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--
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-- The backfill is deterministic rather than a guess: `store_derived_blob` has
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-- only ever been called with `"image/webp"` for thumbnails, so every existing
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-- thumbnail row is WebP. `content_type` is checked anyway rather than assumed
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-- — if that assumption is ever wrong, the row is left alone for a human to
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-- look at instead of being silently mislabelled.
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UPDATE storage.content_derived_blobs
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SET variant = variant || '.webp'
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WHERE kind = 'thumbnail'
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AND content_type = 'image/webp'
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-- Idempotent: skip anything already carrying a format suffix, so a
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-- re-applied migration cannot produce `preview.webp.webp`.
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AND variant NOT LIKE '%.%';
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-- Anything left without a format suffix did not match the WebP assumption.
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-- Surfaced as a warning rather than coerced: the read path will simply miss
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-- those rows and fall back to the sidecar, which is safe, whereas guessing a
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-- codec would serve the wrong bytes.
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DO $$
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DECLARE
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v_unsuffixed INT;
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BEGIN
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SELECT COUNT(*) INTO v_unsuffixed
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FROM storage.content_derived_blobs
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WHERE kind = 'thumbnail' AND variant NOT LIKE '%.%';
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IF v_unsuffixed > 0 THEN
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RAISE WARNING
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'derived_variant_encodes_format: % thumbnail row(s) have no format suffix (content_type was not image/webp). They will be ignored by the read path and re-derived on demand; inspect before deleting the sidecars.',
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v_unsuffixed;
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END IF;
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END $$;
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COMMENT ON COLUMN storage.content_derived_blobs.variant IS
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'Opaque discriminator carrying every axis but the source and the kind: size AND output format, as {size}.{ext} (preview.webp | icon.jpg | 720p.webp). New axes go inside this string, never into new columns. A format term is required — without one, two codecs of the same source collide on the primary key, and the read path cannot tell which codec a row holds.';
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