![]() Without a partition_spec the table is truncated before inserting the first row.If you specify OVERWRITE the following applies: If schema evolution is enabled, new columns can exist as the last columns of your schema (or nested columns) for the schema to evolve. If a column’s data type cannot be safely cast to a Delta table’s data type, a runtime exception is thrown. Raise exception 'Explicit insert into serial id, currval = %, tried to insert = %', currval(pg_get_serial_sequence(TG_TABLE_NAME, 'id')), new.When you INSERT INTO a Delta table, schema enforcement and evolution is supported. If new.id > currval(pg_get_serial_sequence(TG_TABLE_NAME, 'id')) then (Note that pg_get_serial_sequence relies on the sequence's OWNED BY property being correctly set.) create or replace function serial_id_check() returns trigger as Also note the use of pg_get_serial_sequence to more reliably determine the name of the sequence. This slight fix to the trigger condition fixes that issue. The OPs own solution does break in the scenario where you do multiple inserts via either INSERT INTO table (col2) VALUES ('val'), ('val') or INSERT INTO table (col2) SELECT somefield FROM anothertable. The approved answer is all good, but when trying to troubleshoot a scenario where code from somewhere appears to be inserting explicit ID values and thereby breaking the sequence down the road, you really want to raise an error to the offending code instead of simply fixing the problem on the fly (or rewriting everything to use a view). Still assuming the column name id which I personally never use since it's not descriptive. Think of "MyTable" or a non-default sequence name. Note the use of pg_get_serial_sequence(), which won't break like your original for non-basic identifiers. How to prevent a PostgreSQL trigger from being fired by another trigger?.You could fine-tune the UPDATE case with a separate trigger and a condition on the trigger itself WHEN (OLD.id NEW.id). Then you rely on the trigger exclusively. Typically, gaps in a sequence should not be a problem (to be expected anyway), but you can avoid the side effect by removing the DEFAULT from the column. Like commented, this burns two numbers per row in normal operation with a serial column because a default is fetched before the trigger function kicks in. quote_ident() to safely escape otherwise illegal names (also defends against SQL injection). That's simpler and cheaper and less error-prone than trying to be smart about it. NEW.id := nextval(pg_get_serial_sequence(quote_ident(TG_TABLE_NAME), 'id')) Simple triggerĪlternatively, you could simply overwrite the serial column with the next value from its sequence unconditionally: CREATE OR REPLACE FUNCTION force_serial_id() Important difference: while the automatically updatable view rejects attempts to INSERT / UPDATE values in id with an exception, the demonstrated RULE simply ignores values for id and proceeds without exception. Now, INSERT on the view is possible, but not yet UPDATE or DELETE. INSERT INTO test_table (foobar) VALUES (NEW.foobar) ![]() Example: CREATE VIEW test_view1 AS TABLE test_table You might want to use this even in Postgres 9.4+ to fine-tune functionality. While writing rules / triggers manually, you don't need the id * 1 trick. In Postgres 9.3 or older, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule. Automatically updatable views were introduced with Postgres 9.3, but all columns need to be updatable in that version for the feature to work. This simple and quick solution works out of the box in Postgres 9.4. Now they can do everything, but they cannot manually set or alter the value in id. GRANT INSERT / UPDATE on test_view to your users.Make another role holding those privileges own the view.REVOKE INSERT / UPDATE privileges on test_table from your users.SELECT id * 1 AS id - id unchanged but not updatable!īy multiplying id with 1, the value is unchanged but the column is not automatically updatable any more. We can exploit this feature: CREATE TABLE test_table( I.e., as long as basic conditions are met, columns are automatically updatable for plain references to underlying columns. In Postgres 9.4, views are automatically updatable per column. Original answer for older versions: Updateable View Like: id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY In Postgres 10 or later, consider an IDENTITY column instead.
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