pgsql: Fix incorrect Datum conversion in timestamptz_trunc_internal()

Fix incorrect Datum conversion in timestamptz_trunc_internal()

The code used a PG_RETURN_TIMESTAMPTZ() where the return type is
TimestampTz and not a Datum.

On 64-bit systems, there is no effect since this just ends up casting
64-bit integers back and forth. On 32-bit systems, timestamptz is
pass-by-reference. PG_RETURN_TIMESTAMPTZ() allocates new memory and
returns the address, meaning that the caller could interpret this as a
timestamp value.

The effect is using "date_trunc(..., 'infinity'::timestamptz) will
return random values (instead of the correct return value 'infinity').

Bug introduced in commit d85ce012f99f.

Author: Peter Eisentraut <peter(at)eisentraut(dot)org>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/[email protected]
Discussion: https://postgr.es/m/[email protected]
Backpatch-through: 18

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2242b26ce472db9ac69dc71008c566ea9cd3a5fd

Modified Files
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src/backend/utils/adt/timestamp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)