On 1/16/26 02:32, Dominique Devienne wrote:
On Fri, Jan 16, 2026 at 10:13 AM Marcelo Fernandes <[email protected]> wrote:
From the documentation:
TRUNCATE quickly removes all rows from a set of tables. It has the same
effect as an unqualified DELETE on each table, but since it does not actually
scan the tables it is faster.
(...)
You must have the TRUNCATE privilege on a table to truncate it.
Granted that TRUNCATE and DELETE are different operations under the hood, but
why would the TRUNCATE operation require its own specific privilege rather than
say, use the same privilege as the DELETE operation?
It's kinda obvious, when you read the notes.
1) Not MVCC-safe.
2) Do not fire TRIGGERs, thus breaking data-integrity
It will not fire ON DELETE triggers, it will fire ON TRUNCATE triggers.
3) "Viral" in the presence of FKs, i.e. related tables must also be TRUNCATEd
Only if you add the CASCADE option, or TRUNCATE them in the same
command. Otherwise it will fail.
Just these 3 are HUGE departures from a DELETE. --DD
I would add from:
https://www.postgresql.org/docs/current/sql-truncate.html
"TRUNCATE acquires an ACCESS EXCLUSIVE lock on each table it operates
on, which blocks all other concurrent operations on the table. When
RESTART IDENTITY is specified, any sequences that are to be restarted
are likewise locked exclusively. If concurrent access to a table is
required, then the DELETE command should be used instead."
and
""
When RESTART IDENTITY is specified, the implied ALTER SEQUENCE RESTART
operations are also done transactionally; that is, they will be rolled
back if the surrounding transaction does not commit. Be aware that if
any additional sequence operations are done on the restarted sequences
before the transaction rolls back, the effects of these operations on
the sequences will be rolled back, but not their effects on currval();
that is, after the transaction currval() will continue to reflect the
last sequence value obtained inside the failed transaction, even though
the sequence itself may no longer be consistent with that. This is
similar to the usual behavior of currval() after a failed transaction."
--
Adrian Klaver
[email protected]
