Declare only the tables and columns pixa writes and reads (closes #310)

Removes output_content and request_cache, which nothing writes, and every
column that was written but never read: the host, path, query and
fetched_at of source_content, the content_type and created_at of
variant_content, and the status_code, error_message and fetched_at of
negative_cache.

StoreVariant no longer takes a content type and StoreNegative no longer
takes a status code or message, so extractStatusCode and the status
constants, which only fed status_code, are gone. Reconciliation adopts a
variant file without opening it, as its row no longer records a content
type. Tests that set or checked a removed column follow.

Model: opus-5-5

internal/imgcache/cache.go

@@ -231,17 +231,13 @@ func (c *Cache) StoreSource(
 	}
 
 	_, err = c.db.ExecContext(ctx, `
-		INSERT INTO source_content
-			(source_key, source_host, source_path, source_query,
-			 content_type, size_bytes)
-		VALUES (?, ?, ?, ?, ?, ?)
+		INSERT INTO source_content (source_key, content_type, size_bytes)
+		VALUES (?, ?, ?)
 		ON CONFLICT(source_key) DO UPDATE SET
 			content_type = excluded.content_type,
 			size_bytes = excluded.size_bytes,
-			fetched_at = CURRENT_TIMESTAMP,
 			last_accessed_at = CURRENT_TIMESTAMP
-	`, string(key), req.Source.Host, req.Source.Path, req.Source.Query,
-		result.ContentType, size)
+	`, string(key), result.ContentType, size)
 	if err != nil {
 		deleteErr := c.srcContent.Delete(key)
 		if deleteErr != nil {
@@ -262,8 +258,7 @@ func (c *Cache) StoreSource(
 // accounting insert is best-effort (the startup reconciliation pass
 // adopts any variant file that misses its accounting row).
 func (c *Cache) StoreVariant(
-	ctx context.Context, cacheKey imagerequest.VariantKey,
-	content io.Reader, contentType string,
+	ctx context.Context, cacheKey imagerequest.VariantKey, content io.Reader,
 ) error {
 	if c.disabled {
 		return nil
@@ -275,13 +270,12 @@ func (c *Cache) StoreVariant(
 	}
 
 	_, err = c.db.ExecContext(ctx, `
-		INSERT INTO variant_content (cache_key, size_bytes, content_type)
-		VALUES (?, ?, ?)
+		INSERT INTO variant_content (cache_key, size_bytes)
+		VALUES (?, ?)
 		ON CONFLICT(cache_key) DO UPDATE SET
 			size_bytes = excluded.size_bytes,
-			content_type = excluded.content_type,
 			last_accessed_at = CURRENT_TIMESTAMP
-	`, string(cacheKey), size, contentType)
+	`, string(cacheKey), size)
 	if err != nil {
 		c.log.Warn("failed to record variant in size accounting",
 			"cache_key", cacheKey, "error", err)
@@ -331,22 +325,16 @@ func (c *Cache) LookupSource(
 }
 
 // StoreNegative stores a negative cache entry for a failed fetch.
-func (c *Cache) StoreNegative(
-	ctx context.Context, req *imagerequest.Request, statusCode int, errMsg string,
-) error {
+func (c *Cache) StoreNegative(ctx context.Context, req *imagerequest.Request) error {
 	expiresAt := time.Now().UTC().Add(c.config.NegativeTTL)
 
 	_, err := c.db.ExecContext(ctx, `
 		INSERT INTO negative_cache
-			(source_host, source_path, source_query, status_code,
-			 error_message, expires_at)
-		VALUES (?, ?, ?, ?, ?, ?)
+			(source_host, source_path, source_query, expires_at)
+		VALUES (?, ?, ?, ?)
 		ON CONFLICT(source_host, source_path, source_query) DO UPDATE SET
-			status_code = excluded.status_code,
-			error_message = excluded.error_message,
-			fetched_at = CURRENT_TIMESTAMP,
 			expires_at = excluded.expires_at
-	`, req.Source.Host, req.Source.Path, req.Source.Query, statusCode, errMsg, expiresAt)
+	`, req.Source.Host, req.Source.Path, req.Source.Query, expiresAt)
 	if err != nil {
 		return fmt.Errorf("failed to insert negative cache: %w", err)
 	}