ORDER-INDEPENDENT rollup of a partition's records into a single hash. Each record's mapped fields
are content-hashed via computeContentHash, the per-record hashes are SORTED, then the sorted list
is concatenated and SHA-256'd. Sorting before combining is what makes the rollup stable regardless
of the order records were fetched in — [a,b] and [b,a] produce the identical partition digest,
so a re-fetch that merely reorders rows never spuriously flags the partition as changed.
An empty partition rolls up to the SHA-256 of the empty string, a stable sentinel distinct from any
non-empty partition.
ORDER-INDEPENDENT rollup of a partition's records into a single hash. Each record's mapped fields are content-hashed via
computeContentHash, the per-record hashes are SORTED, then the sorted list is concatenated and SHA-256'd. Sorting before combining is what makes the rollup stable regardless of the order records were fetched in —[a,b]and[b,a]produce the identical partition digest, so a re-fetch that merely reorders rows never spuriously flags the partition as changed.An empty partition rolls up to the SHA-256 of the empty string, a stable sentinel distinct from any non-empty partition.