Partition files by age (id)

New rows went into free space scattered through the 9.6 GB heap on the HDD
(left behind by inspection's updates): one random HDD read per insert, and
seed batches took a median 13 s to store. The existing table becomes the
first partition as it is (a CHECK scan, no rewrite; indexes, its foreign
key and the triggers are taken over by the partitioned parent); new
partitions of 4M ids go in the same tablespace and stay in memory while
they fill.

- Every partition has a unique file_key index; FileStore.insert looks keys
  up in all partitions first (a key can't be unique across partitions).
- FilePartitions.ensure() (gc:scheduler) keeps two partitions ahead.
- Stats count files from the partitions; seed:node waits ~20 minutes for
  the API before giving a range up.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/services/FilePartitions.ts

@@ -0,0 +1,39 @@
+import db from '@adonisjs/lucid/services/db'
+import logger from '@adonisjs/core/services/logger'
+
+/** Ids per partition (as the migration that partitioned files: …150). */
+export const FILE_PARTITION_SIZE = 4_000_000
+/** Ids kept covered beyond the newest file: two partitions. */
+const AHEAD = 2 * FILE_PARTITION_SIZE
+
+/**
+ * `files` is partitioned by id (CONCEPT.md D39). An insert with an id no
+ * partition covers fails, so gc:scheduler calls ensure() every sweep to keep
+ * two partitions ready ahead of the newest id. Each new partition gets its
+ * own unique index on file_key (FileStore.insert checks the older ones),
+ * in the parent's tablespace (the HDD on homelab).
+ */
+class FilePartitions {
+  async ensure(): Promise<string[]> {
+    const created: string[] = []
+    while (true) {
+      const { rows } = await db.rawQuery(
+        `SELECT (SELECT coalesce(max(id), 0) FROM files) AS max_id,
+                -- ''{0,1}, not ''?: knex reads ? as a binding.
+                max((regexp_match(pg_get_expr(c.relpartbound, c.oid), 'TO \\(''{0,1}(\\d+)''{0,1}\\)'))[1]::bigint) AS upper
+         FROM pg_inherits i JOIN pg_class c ON c.oid = i.inhrelid
+         WHERE i.inhparent = 'files'::regclass`
+      )
+      const maxId = Number(rows[0].max_id)
+      const upper = Number(rows[0].upper)
+      if (upper - maxId >= AHEAD) return created
+      const name = `files_p${upper}`
+      await db.rawQuery(`CREATE TABLE ${name} PARTITION OF files FOR VALUES FROM (${upper}) TO (${upper + FILE_PARTITION_SIZE})`)
+      await db.rawQuery(`ALTER TABLE ${name} ADD CONSTRAINT ${name}_file_key_unique UNIQUE (file_key)`)
+      logger.info(`files: partition ${name} created (ids ${upper}–${upper + FILE_PARTITION_SIZE - 1}).`)
+      created.push(name)
+    }
+  }
+}
+
+export default new FilePartitions()