psql helpers for CID inspection

scripts/cid_decode.sql

@@ -0,0 +1,78 @@
+-- Decode singularity's bytea CID columns (the raw cid.Bytes() form, e.g.
+-- car_blocks.cid, cars.piece_cid, cars.root_cid) into the canonical CID
+-- string, matching go-cid's Cid.String(). Pure PL/pgSQL, no extension needed.
+--   CIDv1 -> multibase base32 with a leading 'b'  (bafy…/bafk…/baga…)
+--   CIDv0 -> base58btc, no prefix                 (Qm…)
+--
+-- usage:
+--   SELECT cid_str(cid) FROM car_blocks WHERE file_id = 123 LIMIT 20;
+--   SELECT cid_str(piece_cid), cid_str(root_cid) FROM cars WHERE id = 456;
+-- cid_str is IMMUTABLE, so it can also back a functional index or a
+-- GENERATED ALWAYS AS (cid_str(cid)) STORED column. It's per-row PL/pgSQL,
+-- so filter (WHERE/LIMIT) rather than scanning all of car_blocks.
+
+-- base32, lowercase, RFC 4648, no padding (CIDv1 multibase 'b')
+CREATE OR REPLACE FUNCTION cid_b32(data bytea) RETURNS text
+LANGUAGE plpgsql IMMUTABLE STRICT AS $$
+DECLARE
+  alpha CONSTANT text := 'abcdefghijklmnopqrstuvwxyz234567';
+  out text := '';
+  buf  int  := 0;
+  bits int  := 0;
+  i    int;
+BEGIN
+  FOR i IN 0 .. length(data)-1 LOOP
+    buf  := (buf << 8) | get_byte(data, i);
+    bits := bits + 8;
+    WHILE bits >= 5 LOOP
+      bits := bits - 5;
+      out  := out || substr(alpha, ((buf >> bits) & 31) + 1, 1);
+    END LOOP;
+    buf := buf & ((1 << bits) - 1);   -- keep only the leftover bits (avoid int overflow)
+  END LOOP;
+  IF bits > 0 THEN
+    out := out || substr(alpha, ((buf << (5 - bits)) & 31) + 1, 1);
+  END IF;
+  RETURN out;
+END $$;
+
+-- base58btc (Bitcoin alphabet)
+CREATE OR REPLACE FUNCTION cid_b58(data bytea) RETURNS text
+LANGUAGE plpgsql IMMUTABLE STRICT AS $$
+DECLARE
+  alpha CONSTANT text := '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz';
+  n     numeric := 0;
+  out   text := '';
+  i     int;
+  zeros int := 0;
+BEGIN
+  WHILE zeros < length(data) AND get_byte(data, zeros) = 0 LOOP   -- leading 0x00 -> '1'
+    zeros := zeros + 1;
+  END LOOP;
+  FOR i IN 0 .. length(data)-1 LOOP                               -- big-endian bytes -> bignum
+    n := n * 256 + get_byte(data, i);
+  END LOOP;
+  WHILE n > 0 LOOP
+    out := substr(alpha, (n % 58)::int + 1, 1) || out;
+    n   := div(n, 58);
+  END LOOP;
+  RETURN repeat('1', zeros) || out;
+END $$;
+
+-- main entry point: bytea CID -> canonical string
+CREATE OR REPLACE FUNCTION cid_str(data bytea) RETURNS text
+LANGUAGE plpgsql IMMUTABLE STRICT AS $$
+BEGIN
+  IF length(data) = 0 THEN
+    RETURN NULL;
+  END IF;
+  -- CIDv0: bare 34-byte sha2-256 multihash (0x12 0x20 …)
+  IF length(data) = 34 AND get_byte(data,0) = 18 AND get_byte(data,1) = 32 THEN
+    RETURN cid_b58(data);
+  END IF;
+  -- CIDv1: version byte 0x01 -> base32 multibase
+  IF get_byte(data,0) = 1 THEN
+    RETURN 'b' || cid_b32(data);
+  END IF;
+  RETURN NULL;   -- not a CID we recognize
+END $$;