Changeset 0.8.0 (#39)

server/database/migrations/013_message_forking.sql

@@ -0,0 +1,28 @@
+-- ==========================================
+-- Migration 013: Message Forking Support
+-- ==========================================
+-- Adds soft delete and sibling ordering to support
+-- conversation forking (edit, regenerate, branch).
+-- See ARCHITECTURE.md §8 for the full tree model.
+-- ==========================================
+
+-- Soft delete: pruned branches keep their structure for undo
+ALTER TABLE messages ADD COLUMN IF NOT EXISTS deleted_at TIMESTAMPTZ;
+
+-- Sibling ordering: explicit position among children of same parent
+-- First child = 0, second = 1, etc. Set at insert time.
+ALTER TABLE messages ADD COLUMN IF NOT EXISTS sibling_index INTEGER DEFAULT 0;
+
+-- Partial index: fast lookup of live messages only
+CREATE INDEX IF NOT EXISTS idx_messages_alive
+    ON messages(channel_id, created_at)
+    WHERE deleted_at IS NULL;
+
+-- Children of a parent (for sibling queries)
+CREATE INDEX IF NOT EXISTS idx_messages_parent_alive
+    ON messages(parent_id, sibling_index)
+    WHERE deleted_at IS NULL;
+
+-- Backfill sibling_index for existing messages.
+-- In linear conversations every message is the sole child of its parent,
+-- so all get sibling_index = 0 (already the default). No update needed.