Postgres 12

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CREATE TABLE t(amount) AS
SELECT round((random() * generate_series (1,100000))::numeric, 2);
100000 rows affected

VACUUM ANALYZE t;
EXPLAIN (ANALYZE, TIMING OFF, COSTS OFF)
SELECT count(*) FROM t WHERE amount <> trunc(amount);

QUERY PLAN

Aggregate (actual rows=1 loops=1)

  ->  Seq Scan on t (actual rows=99056 loops=1)

        Filter: (amount <> trunc(amount, 0))

        Rows Removed by Filter: 944

Planning Time: 0.314 ms

Execution Time: 34.885 ms

EXPLAIN (ANALYZE, TIMING OFF, COSTS OFF)
SELECT count(*) FROM t WHERE amount != round(amount);

QUERY PLAN

Aggregate (actual rows=1 loops=1)

  ->  Seq Scan on t (actual rows=99056 loops=1)

        Filter: (amount <> round(amount, 0))

        Rows Removed by Filter: 944

Planning Time: 0.069 ms

Execution Time: 36.095 ms

EXPLAIN (ANALYZE, TIMING OFF, COSTS OFF)
SELECT count(*) FROM t WHERE amount <> amount::int;

QUERY PLAN

Aggregate (actual rows=1 loops=1)

  ->  Seq Scan on t (actual rows=99056 loops=1)

        Filter: (amount <> ((amount)::integer)::numeric)

        Rows Removed by Filter: 944

Planning Time: 0.051 ms

Execution Time: 41.392 ms

EXPLAIN (ANALYZE, TIMING OFF, COSTS OFF)
SELECT count(*) FROM t WHERE round(amount,2) != round(amount);

QUERY PLAN

Aggregate (actual rows=1 loops=1)

  ->  Seq Scan on t (actual rows=99056 loops=1)

        Filter: (round(amount, 2) <> round(amount, 0))

        Rows Removed by Filter: 944

Planning Time: 0.069 ms

Execution Time: 45.788 ms

EXPLAIN (ANALYZE, TIMING OFF, COSTS OFF)
SELECT count(*) FROM t WHERE amount <> amount::bigint;

QUERY PLAN

Aggregate (actual rows=1 loops=1)

  ->  Seq Scan on t (actual rows=99056 loops=1)

        Filter: (amount <> ((amount)::bigint)::numeric)

        Rows Removed by Filter: 944

Planning Time: 0.057 ms

Execution Time: 40.146 ms

EXPLAIN (ANALYZE, TIMING OFF, COSTS OFF)
SELECT count(*) FROM t WHERE amount <> floor(amount);

QUERY PLAN

Aggregate (actual rows=1 loops=1)

  ->  Seq Scan on t (actual rows=99056 loops=1)

        Filter: (amount <> floor(amount))

        Rows Removed by Filter: 944

Planning Time: 0.072 ms

Execution Time: 36.532 ms

EXPLAIN (ANALYZE, TIMING OFF, COSTS OFF)
SELECT count(*) FROM t WHERE amount - floor(amount) > .00;

QUERY PLAN

Aggregate (actual rows=1 loops=1)

  ->  Seq Scan on t (actual rows=99056 loops=1)

        Filter: ((amount - floor(amount)) > 0.00)

        Rows Removed by Filter: 944

Planning Time: 0.080 ms

Execution Time: 47.603 ms