SortSupport is a Postgres optimization technique that speeds up sorting of pass-by-reference types (like UUIDs, text, and macaddr) by generating compact 'abbreviated keys' — pointer-sized digests of full heap values — that fit directly into sort tuples. This avoids expensive heap lookups during comparisons. The abbreviated key for UUIDs, for example, takes the first 64 bits and compares them as native integers (with byte-swapping for endianness correctness). If two abbreviated keys are equal, Postgres falls back to a full authoritative comparison. To guard against low-cardinality datasets where abbreviation would hurt performance, SortSupport uses HyperLogLog to estimate distinct value counts and aborts abbreviation if cardinality is too low. The technique typically doubles or triples performance for ORDER BY, DISTINCT, and CREATE INDEX operations.
