WITH cand AS (
  SELECT
    $1::bytea AS b,                         -- $1 is the input parameter; cast to BYTEA (not a function, a cast)
    length($1::bytea) AS n                  -- length(bytea): number of bytes in the candidate bytecode
)
SELECT
  b.id,
  b.normalized_bytecode,
  b.diff_offsets
FROM bytecode_norm AS b
JOIN cand c
  ON c.n = b.nbytes                         -- (no function) prefilter by total length
WHERE NOT EXISTS (                           -- NOT EXISTS: ensures there is NO mismatching kept segment
-- this part can be a bit tricky:
-- basically here we are putting the diff offsets of each row in the select
-- in a virtual table
-- then we are checking for each of these chunks if it's included in the candidate
  SELECT 1
  FROM unnest(                               -- unnest(anymultirange): expands a multirange into its constituent ranges
         (multirange(                        -- multirange(range): wraps a single range into a multirange
            int4range(0, b.nbytes)          -- int4range(lower, upper): constructs [lower, upper) over int4 (here [0, nbytes))
          )
          - COALESCE(
              b.diff_offsets,                --   diff_offsets is an int4multirange of masked (ignored) byte spans
              '{}'::int4multirange          --   empty multirange when there are no diffs
            )
        )
       ) AS r
  WHERE substr(                               -- substr(bytea, start, length): slice of BYTEA; start is 1-based
          c.b,
          lower(r) + 1,                      -- lower(range): lower bound of range r (0-based); +1 to convert to 1-based for substr
          upper(r) - lower(r)                -- upper(range): upper bound of r; (upper - lower) is the segment length
        )
     <> substr(                               -- compare the same kept slice of the stored normalized bytecode
          b.normalized_bytecode,
          lower(r) + 1,
          upper(r) - lower(r)
        )
);