Wrong result when reducing timestamp precision in a cast to timestamp with time zone

[hk8suva]

Trino version

483

Please describe the bug

Trino incorrectly returns zero rows when a timestamp(9) is cast to timestamp(6) with time zone inside a filter.

Reproduction

SELECT count(*) FROM ( VALUES CAST( TIMESTAMP '2026-07-26 03:00:00' AS timestamp(9) ) ) t(lastupdate) WHERE CAST(lastupdate AS timestamp(6) WITH TIME ZONE) > TIMESTAMP '2026-07-25 00:00:00 UTC';

Expected result: 1 (The timestamp is later than the value used in the filter.)
Actual result: 0

EXPLAIN shows that Trino removes the input during planning:

Trino version: 483
Fragment 0 [SINGLE]
    Output layout: [count]
    Output partitioning: SINGLE []
    Output[columnNames = [_col0]]
    │   Layout: [count:bigint]
    │   Estimates: {rows: 1 (9B), cpu: 0, memory: 0B, network: 0B}
    │   _col0 := count
    └─ Aggregate[]
       │   Layout: [count:bigint]
       │   Estimates: {rows: 1 (9B), cpu: 0, memory: 9B, network: 0B}
       │   count := count(*)
       └─ Values[]
              Layout: []
              Estimates: {rows: 0 (0B), cpu: 0, memory: 0B, network: 0B}

Working variants

SELECT count(*) FROM ( VALUES CAST( TIMESTAMP '2026-07-26 03:00:00' AS timestamp(9) ) ) t(lastupdate) WHERE CAST(lastupdate AS timestamp(9) WITH TIME ZONE) > CAST( TIMESTAMP '2026-07-25 00:00:00 UTC' AS timestamp(9) WITH TIME ZONE );

or

SELECT count(*) FROM ( VALUES CAST( TIMESTAMP '2026-07-26 03:00:00' AS timestamp(9) ) ) t(lastupdate) WHERE with_timezone(lastupdate, 'Europe/Zurich') > TIMESTAMP '2026-07-25 00:00:00 UTC';

The problem seems to occur specifically when the cast reduces the precision from timestamp(9) to timestamp(6).