On 23 Mar 2026 at 14:57 +0100, jian he <jian.universality@gmail.com>, wrote:
hi.
https://postgr.es/m/CAEze2Wi4M1grsR0q27etuB-jncJ6qN-1FMdRX-2PkQxcFpM3sQ@mail.gmail.com
Make me realize that ArrayCoerceExpr (one type of array cast to
another type of array) table rewrite is necessary.
For example, the following will cause a table rewrite:
+CREATE TABLE t22(a INT, b INT, c text COLLATE "C", col1 INT[]);
+CREATE DOMAIN domain1 AS INT CHECK(VALUE > 1) NOT NULL;
+CREATE DOMAIN domain2 AS domain1 CHECK(VALUE > 1) NOT NULL;
+CREATE DOMAIN domain6 AS domain2[];
+ALTER TABLE t22 ALTER COLUMN col1 SET DATA TYPE domain6 USING col1;
Now: if the new type is a constrained domain over the old type,
tablescan is enough.
ATColumnChangeRequiresRewrite works just as before.
--
jian
This appears to address some of my comments but not this one?
CREATE DOMAIN domain1 AS INT CHECK(VALUE > 1) NOT NULL;
CREATE TABLE t_const_using(a INT);
INSERT INTO t_const_using VALUES(-2);
ALTER TABLE t_const_using ALTER COLUMN a SET DATA TYPE domain1 USING 5;
SELECT a FROM t_const_using; -- should be 5 after rewrite, not -2
a
----
-2
