DROP TABLE IF EXISTS codecTest; CREATE TABLE codecTest ( key UInt64, name String, ref_valueF64 Float64, ref_valueF32 Float32, valueF64 Float64 CODEC(Gorilla), valueF32 Float32 CODEC(Gorilla) ) Engine = MergeTree ORDER BY key; -- best case - same value INSERT INTO codecTest (key, name, ref_valueF64, valueF64, ref_valueF32, valueF32) SELECT number AS n, 'e()', e() AS v, v, v, v FROM system.numbers LIMIT 1, 100; -- good case - values that grow insignificantly INSERT INTO codecTest (key, name, ref_valueF64, valueF64, ref_valueF32, valueF32) SELECT number AS n, 'log2(n)', log2(n) AS v, v, v, v FROM system.numbers LIMIT 101, 100; -- bad case - values differ significantly INSERT INTO codecTest (key, name, ref_valueF64, valueF64, ref_valueF32, valueF32) SELECT number AS n, 'n*sqrt(n)', n*sqrt(n) AS v, v, v, v FROM system.numbers LIMIT 201, 100; -- worst case - almost like a random values INSERT INTO codecTest (key, name, ref_valueF64, valueF64, ref_valueF32, valueF32) SELECT number AS n, 'sin(n*n*n)*n', sin(n * n * n * n* n) AS v, v, v, v FROM system.numbers LIMIT 301, 100; -- These floating-point values are expected to be BINARY equal, so comparing by-value is Ok here. -- referencing previous row key, value, and case name to simplify debugging. SELECT 'F64'; SELECT c1.key, c1.name, c1.ref_valueF64, c1.valueF64, c1.ref_valueF64 - c1.valueF64 AS dF64, 'prev:', c2.key, c2.ref_valueF64 FROM codecTest as c1, codecTest as c2 WHERE dF64 != 0 AND c2.key = c1.key - 1 LIMIT 10; SELECT 'F32'; SELECT c1.key, c1.name, c1.ref_valueF32, c1.valueF32, c1.ref_valueF32 - c1.valueF32 AS dF32, 'prev:', c2.key, c2.ref_valueF32 FROM codecTest as c1, codecTest as c2 WHERE dF32 != 0 AND c2.key = c1.key - 1 LIMIT 10; DROP TABLE IF EXISTS codecTest;