v2-0001-get-the-base-type-of-a-domain.patch

From 55a64f371e34ae62928fef57928256456ceda5cd Mon Sep 17 00:00:00 2001
From: pgaddict <jian.universality@gmail.com>
Date: Sat, 18 Nov 2023 00:08:08 +0800
Subject: [PATCH v2 1/1] get the base type of a domain.

Mainly used for get the base type of a domain.
Currently obtaining the base type of a domain involves
a long SQL query, this specially in the case of recursive domain types.

To solve this, add another function: getBaseTypeAndTypmodExtended,
and expose it to pg_basetype SQL function.

function getBaseTypeAndTypmodExtended the same as getBaseTypeAndTypmod,
except that the third arg is missing_ok (bool).

If missing_ok is true, type syscache search can not found, it will return InvalidOid.
If missing_ok is false, type syscache cannot found, it will return error.
---
 doc/src/sgml/func.sgml               | 25 ++++++++++++++
 src/backend/utils/adt/misc.c         | 18 ++++++++++
 src/backend/utils/cache/lsyscache.c  | 49 ++++++++++++++++++++++++++++
 src/include/catalog/pg_proc.dat      |  4 +++
 src/include/utils/lsyscache.h        |  2 ++
 src/test/regress/expected/domain.out | 36 ++++++++++++++++++++
 src/test/regress/sql/domain.sql      | 17 ++++++++++
 7 files changed, 151 insertions(+)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 93f068ed..ad1c2b26 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -24361,6 +24361,31 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_basetype</primary>
+        </indexterm>
+        <function>pg_basetype</function> ( <parameter>type</parameter> <type>oid</type> )
+        <returnvalue>regtype</returnvalue>
+       </para>
+       <para>
+       Returns the OID of the base type of a domain or if the argument is not a domain, returns the argument.
+       If there's a chain of domain dependencies, it will recurse until finding the base type.
+       </para>
+       <para>
+        For example:
+<programlisting>
+CREATE DOMAIN mytext as text;
+
+SELECT pg_basetype('mytext'::regtype);
+ pg_basetype
+-----------
+ text
+</programlisting>
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-char-to-encoding" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 5d78d6dc..0bb5453b 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -45,6 +45,7 @@
 #include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
 #include "utils/ruleutils.h"
+#include "utils/syscache.h"
 #include "utils/timestamp.h"
 
 
@@ -566,6 +567,23 @@ pg_typeof(PG_FUNCTION_ARGS)
 	PG_RETURN_OID(get_fn_expr_argtype(fcinfo->flinfo, 0));
 }
 
+/*
+ * Return the base type of the argument.
+ */
+Datum
+pg_basetype(PG_FUNCTION_ARGS)
+{
+	Oid			oid = PG_GETARG_OID(0);
+	int32		base_typmod = -1;
+	Oid			result;
+
+	result = getBaseTypeAndTypmodExtended(oid, &base_typmod, true);
+
+	if (!OidIsValid(result))
+		PG_RETURN_NULL();
+
+	PG_RETURN_OID(result);
+}
 
 /*
  * Implementation of the COLLATE FOR expression; returns the collation
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index fc6d267e..ce9abcfa 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -2548,6 +2548,55 @@ getBaseTypeAndTypmod(Oid typid, int32 *typmod)
 	return typid;
 }
 
+/*
+ * getBaseTypeAndTypmodExtended
+ *		If the given type is a domain, return its base type and typmod;
+ *		otherwise return the type's own OID, and leave *typmod unchanged.
+ *   	If missing_ok is false, throw an error if base type not found.
+ * 		If missing_ok is true, return InvalidOid if base type not found.
+ *
+ * Note that the "applied typmod" should be -1 for every domain level
+ * above the bottommost; therefore, if the passed-in typid is indeed
+ * a domain, *typmod should be -1.
+ */
+Oid
+getBaseTypeAndTypmodExtended(Oid typid, int32 *typmod, bool missing_ok)
+{
+	/*
+	 * We loop to find the bottom base type in a stack of domains.
+	 */
+	for (;;)
+	{
+		HeapTuple	tup;
+		Form_pg_type typTup;
+
+		tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
+		if (HeapTupleIsValid(tup))
+		{
+			typTup = (Form_pg_type) GETSTRUCT(tup);
+			if (typTup->typtype != TYPTYPE_DOMAIN)
+			{
+				/* Not a domain, so done */
+				ReleaseSysCache(tup);
+				break;
+			}
+			Assert(*typmod == -1);
+			typid = typTup->typbasetype;
+			*typmod = typTup->typtypmod;
+
+			ReleaseSysCache(tup);
+		}
+	}
+
+	if(missing_ok && !OidIsValid(typid))
+		return InvalidOid;
+
+	if(!missing_ok && !OidIsValid(typid))
+		elog(ERROR, "cache lookup failed for type %u", typid);
+
+	return typid;
+}
+
 /*
  * get_typavgwidth
  *
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index fb58dee3..725267d9 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3877,6 +3877,10 @@
 { oid => '1619', descr => 'type of the argument',
   proname => 'pg_typeof', proisstrict => 'f', provolatile => 's',
   prorettype => 'regtype', proargtypes => 'any', prosrc => 'pg_typeof' },
+{ oid => '6312', descr => 'get the base type of a domain',
+  proargnames => '{type}',
+  proname => 'pg_basetype', proisstrict => 'f', provolatile => 's',
+  prorettype => 'regtype', proargtypes => 'oid', prosrc => 'pg_basetype' },
 { oid => '3162',
   descr => 'collation of the argument; implementation of the COLLATION FOR expression',
   proname => 'pg_collation_for', proisstrict => 'f', provolatile => 's',
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index c22cabdf..c003ca7a 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -184,6 +184,8 @@ extern const struct SubscriptRoutines *getSubscriptingRoutines(Oid typid,
 															   Oid *typelemp);
 extern Oid	getBaseType(Oid typid);
 extern Oid	getBaseTypeAndTypmod(Oid typid, int32 *typmod);
+extern Oid getBaseTypeAndTypmodExtended(Oid typid, int32 *typmod,
+													bool missing_ok);
 extern int32 get_typavgwidth(Oid typid, int32 typmod);
 extern int32 get_attavgwidth(Oid relid, AttrNumber attnum);
 extern bool get_attstatsslot(AttStatsSlot *sslot, HeapTuple statstuple,
diff --git a/src/test/regress/expected/domain.out b/src/test/regress/expected/domain.out
index 6d94e844..4f0253cd 100644
--- a/src/test/regress/expected/domain.out
+++ b/src/test/regress/expected/domain.out
@@ -1207,3 +1207,39 @@ create domain testdomain1 as int constraint unsigned check (value > 0);
 alter domain testdomain1 rename constraint unsigned to unsigned_foo;
 alter domain testdomain1 drop constraint unsigned_foo;
 drop domain testdomain1;
+--
+-- Get the base type of a domain
+--
+create domain mytext as text;
+create domain mytext_child_1 as mytext;
+create domain mytext_child_2 as mytext_child_1;
+select pg_basetype('mytext'::regtype);
+ pg_basetype 
+-------------
+ text
+(1 row)
+
+-- gets base types recursively
+select pg_basetype('mytext_child_1'::regtype);
+ pg_basetype 
+-------------
+ text
+(1 row)
+
+select pg_basetype('mytext_child_2'::regtype);
+ pg_basetype 
+-------------
+ text
+(1 row)
+
+-- if already a base type, get the same
+select pg_basetype('text'::regtype);
+ pg_basetype 
+-------------
+ text
+(1 row)
+
+drop domain mytext cascade;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to type mytext_child_1
+drop cascades to type mytext_child_2
diff --git a/src/test/regress/sql/domain.sql b/src/test/regress/sql/domain.sql
index 745f5d5f..3c824da0 100644
--- a/src/test/regress/sql/domain.sql
+++ b/src/test/regress/sql/domain.sql
@@ -809,3 +809,20 @@ create domain testdomain1 as int constraint unsigned check (value > 0);
 alter domain testdomain1 rename constraint unsigned to unsigned_foo;
 alter domain testdomain1 drop constraint unsigned_foo;
 drop domain testdomain1;
+
+--
+-- Get the base type of a domain
+--
+
+create domain mytext as text;
+create domain mytext_child_1 as mytext;
+create domain mytext_child_2 as mytext_child_1;
+
+select pg_basetype('mytext'::regtype);
+-- gets base types recursively
+select pg_basetype('mytext_child_1'::regtype);
+select pg_basetype('mytext_child_2'::regtype);
+-- if already a base type, get the same
+select pg_basetype('text'::regtype);
+
+drop domain mytext cascade;
-- 
2.34.1