Re: proposal: schema variables

On Thu, Dec 5, 2024 at 2:52 PM Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>
> Hi
>
> only rebase

hi.
disclaimer, i *only* applied
v20241205-0001-Enhancing-catalog-for-support-session-variables-and-.patch.

create variable v2 as text;
alter variable v2 rename to v2;
ERROR: session variable "v2" already exists in schema "public"

the above is coverage tests for report_namespace_conflict:
case VariableRelationId:
Assert(OidIsValid(nspOid));
msgfmt = gettext_noop("session variable \"%s\" already
exists in schema \"%s\"");
break;

create type t1 as (a int, b int);
CREATE VARIABLE var1 AS t1;
alter type t1 drop attribute a;
should "alter type t1 drop attribute a;" not allowed?

GetCommandLogLevel also needs to deal with case T_CreateSessionVarStmt?

there are no regress tests for the change we made in
find_composite_type_dependencies?
It looks like it will be reachable for sure.

CreateVariable, print out error position:
if (get_typtype(typid) == TYPTYPE_PSEUDO)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("session variable cannot be pseudo-type %s",
format_type_be(typid)),
parser_errposition(pstate, stmt->typeName->location)));

Alvaro Herrera told me actually, you don't need the extra parentheses
around errcode.
so you can:
if (get_typtype(typid) == TYPTYPE_PSEUDO)
ereport(ERROR,
errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("session variable cannot be pseudo-type %s",
format_type_be(typid)),
parser_errposition(pstate, stmt->typeName->location))

pg_variable_is_visible seems to have done twice the system cache call.
maybe follow through with the pg_table_is_visible, pg_type_is_visible
code pattern.

IN src/bin/psql/describe.c
+ appendPQExpBufferStr(&buf, "\nWHERE true\n");
this is not needed?
------------------------------------------------
some of the `foreach` can change to foreach_oid, foreach_node
see: https://git.postgresql.org/cgit/postgresql.git/commit/?id=14dd0f27d7cd56ffae9ecdbe324965073d01a9ff
------------------------------------------------
doc/src/sgml/ref/create_variable.sgml
<programlisting>
CREATE VARIABLE var1 AS date;
LET var1 = current_date;
SELECT var1;
</programlisting>

v20241205-0001-Enhancing-catalog-for-support-session-variables-and-.patch
alone cannot do `LET var1 = current_date;`, `SELECT var1;`
maybe the following patch can do it. but that makes
we cannot commit
v20241205-0001-Enhancing-catalog-for-support-session-variables-and-.patch
alone.
------------------------------------------------
since CREATE VARIABLE is an extension to standard, so in create_schema.sgml
Compatibility section,
do we need to mention CREATE SCHEMA CREATE VARIABLE is an extension
from standard
?
-----------------------------------------------

/*
* Drop variable by OID, and register the needed session variable
* cleanup.
*/
void
DropVariableById(Oid varid)
i am not sure of the meaning of "register the needed session variable cleanup".