Hi, As documented to https://www.postgresql.org/docs/11/arrays.html#ARRAYS-DECLARATION one can create column of an array type using `<typename>[]` form.
Internally, array types get a name in the form of `_<typename>`. This is documented https://www.postgresql.org/docs/11/sql-createtype.html#id-1.9.3.94.5.9 *So -- the question: * *Can a user use `_<typename>` to define a column of array type?* *Is it supported?* The reason I am asking is that e.g. int4[] and _int4 behave differently. Although they look the same, the have different pg_attribute.attndims. I am testing on Postgres 11.2. ================================================ create table t(a int4[], b _int4); \d t Table "public.t" Column | Type | Collation | Nullable | Default --------+-----------+-----------+----------+--------- a | integer[] | | | b | integer[] | | | SELECT attname, attndims FROM pg_attribute att JOIN pg_class tbl ON tbl.oid = att.attrelid WHERE tbl.relname = 't'; attname | attndims ----------+---------- ... * a | 1* * b | 0* ================================================ This has also been discussed previously in 2006 in the https://www.postgresql.org/message-id/8C5B026B51B6854CBE88121DBF097A8651DB95%40ehost010-33.exch010.intermedia.net user group thread. However, it was a while ago (so something might have changed since then) and the conclusion from that discussion wasn't fully clear to me. Best regards, Piotr
