feat(casts): add root_parent tracking for thread identification

migrations/006_add_root_parent_columns.sql

@@ -0,0 +1,18 @@
+-- Add root parent tracking columns for efficient thread identification
+-- Root casts have NULL values; replies have values pointing to the thread root
+
+ALTER TABLE public.casts ADD COLUMN root_parent_fid bigint;
+ALTER TABLE public.casts ADD COLUMN root_parent_hash bytea;
+ALTER TABLE public.casts ADD COLUMN root_parent_url text;
+
+-- Index for efficient thread lookups by root hash
+CREATE INDEX casts_root_parent_hash_index ON public.casts USING btree (root_parent_hash)
+WHERE (root_parent_hash IS NOT NULL);
+
+-- Index for finding threads by author (the FID who started the thread)
+CREATE INDEX casts_root_parent_fid_index ON public.casts USING btree (root_parent_fid)
+WHERE (root_parent_fid IS NOT NULL);
+
+-- Index for finding casts in URL-rooted threads (e.g., channel posts)
+CREATE INDEX casts_root_parent_url_index ON public.casts USING btree (root_parent_url)
+WHERE (root_parent_url IS NOT NULL);

src/backfill/mod.rs

@@ -1,4 +1,5 @@
 pub mod bench;
 pub mod onchain_events;
 pub mod reconciler;
+pub mod root_parent;
 pub mod worker;