sql: add support for REFCURSOR data type

This patch adds support for the `REFCURSOR` type. It is a special type
used to hold the name of a cursor for PLpgSQL, although it can be used
in other contexts (like function return types or column types). `REFCURSOR`
is a string under the hood, and behaves like the `TEXT` data type in most
cases.

`REFCURSOR` has no casts in the `pg_cast` table; instead, all of its
casts are the "IO" string casts. That means that there is an assignment
cast from every type to `REFCURSOR, and an explicit cast from `REFCURSOR`
to every other type (except other string types, which are again assignment).
See `ContextOriginAutomaticIOConversion` in `cast.go` for more info.

This patch also adds `REFCURSOR` to the checks from the previous commit,
so that statements with `REFCURSOR` are disallowed unless all nodes
are running v23.2.

Fixes cockroachdb#111560

Release note (sql change): Added support for the `REFCURSOR` data type.
`REFCURSOR` is a special string type that is used to handle cursors.
PLpgSQL cursor declarations are required to use a variable of type
`REFCURSOR`, and the name of a cursor can be passed to and from a
PLpgSQL function or procedure.

pkg/sql/catalog/colinfo/col_type_info.go

@@ -78,6 +78,14 @@ func ValidateColumnDefType(ctx context.Context, version clusterversion.Handle, t
 				return pgerror.Newf(pgcode.Syntax, `invalid locale %s`, t.Locale())
 			}
 		}
+		if t.Oid() == oid.T_refcursor {
+			if !version.IsActive(ctx, clusterversion.V23_2) {
+				return pgerror.Newf(
+					pgcode.FeatureNotSupported,
+					"refcursor not supported until version 23.2",
+				)
+			}
+		}
 
 	case types.DecimalFamily:
 		switch {

pkg/sql/catalog/colinfo/column_type_properties_test.go

@@ -55,6 +55,7 @@ func TestCanHaveCompositeKeyEncoding(t *testing.T) {
 		{types.Jsonb, true},
 		{types.Name, false},
 		{types.Oid, false},
+		{types.RefCursor, false},
 		{types.String, false},
 		{types.StringArray, false},
 		{types.Time, false},

pkg/sql/logictest/testdata/logic_test/mixed_version_refcursor

@@ -0,0 +1,146 @@
+# LogicTest: cockroach-go-testserver-upgrade-to-master
+
+statement ok
+CREATE TABLE xy (x INT, y INT);
+
+# ----------------------------------------------------------------------
+# Test REFCURSOR references with all nodes running old binaries.
+# ----------------------------------------------------------------------
+
+# Cast to REFCURSOR.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+SELECT 'foo'::REFCURSOR;
+
+# Cast to REFCURSOR using the vectorized engine.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+SELECT 'foo'::REFCURSOR FROM generate_series(1, 100) LIMIT 1;
+
+# Table that references REFCURSOR.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+CREATE TABLE t (x REFCURSOR);
+
+# Add a REFCURSOR column.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+ALTER TABLE xy ADD COLUMN curs REFCURSOR;
+
+# Alter a column type to REFCURSOR.
+statement ok
+SET enable_experimental_alter_column_type_general=true;
+
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+ALTER TABLE xy ALTER COLUMN y TYPE REFCURSOR;
+
+# Create a partial index that uses the REFCURSOR type.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+CREATE INDEX part ON xy (x) WHERE y::REFCURSOR < 'foo';
+
+# Add a check constraint that uses the REFCURSOR type.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+ALTER TABLE xy ADD CONSTRAINT bar CHECK (y::REFCURSOR < 'baz');
+
+# UDT that references REFCURSOR.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+CREATE TYPE typ AS (x INT, y REFCURSOR);
+
+# Function that returns REFCURSOR.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+CREATE OR REPLACE FUNCTION f() RETURNS REFCURSOR AS $$
+  SELECT 'foo';
+$$ LANGUAGE SQL;
+
+# Function that takes REFCURSOR argument.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+CREATE OR REPLACE FUNCTION f(curs REFCURSOR) RETURNS STRING AS $$
+  SELECT curs;
+$$ LANGUAGE SQL;
+
+# Function that references REFCURSOR internally.
+statement error pgcode 42704 pq: type \"refcursor\" does not exist
+CREATE OR REPLACE FUNCTION f() RETURNS INT AS $$
+  SELECT 'foo'::REFCURSOR;
+  SELECT 0;
+$$ LANGUAGE SQL;
+
+# ----------------------------------------------------------------------
+# Verify that REFCURSOR is not allowed after upgrading the gateway.
+# ----------------------------------------------------------------------
+
+upgrade 0
+
+user root nodeidx=0
+
+# Cast to REFCURSOR.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+SELECT 'foo'::REFCURSOR;
+
+# Cast to REFCURSOR using the vectorized engine.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+SELECT 'foo'::REFCURSOR FROM generate_series(1, 100) LIMIT 1;
+
+# Table that references REFCURSOR.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE TABLE t (x REFCURSOR);
+
+# Add a REFCURSOR column.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+ALTER TABLE xy ADD COLUMN curs REFCURSOR;
+
+# Alter a column type to REFCURSOR.
+statement ok
+SET enable_experimental_alter_column_type_general=true;
+
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+ALTER TABLE xy ALTER COLUMN y TYPE REFCURSOR;
+
+# Create a partial index that uses the REFCURSOR type.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE INDEX part ON xy (x) WHERE y::REFCURSOR < 'foo';
+
+# Add a check constraint that uses the REFCURSOR type.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+ALTER TABLE xy ADD CONSTRAINT bar CHECK (y::REFCURSOR < 'baz');
+
+# UDT that references REFCURSOR.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE TYPE typ AS (x INT, y REFCURSOR);
+
+# Function that returns REFCURSOR.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE OR REPLACE FUNCTION f() RETURNS REFCURSOR AS $$
+  SELECT 'foo';
+$$ LANGUAGE SQL;
+
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE OR REPLACE FUNCTION f() RETURNS REFCURSOR AS $$
+  BEGIN
+    RETURN 'foo';
+  END
+$$ LANGUAGE PLpgSQL;
+
+# Function that takes REFCURSOR argument.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE OR REPLACE FUNCTION f(curs REFCURSOR) RETURNS INT AS $$
+  SELECT 0;
+$$ LANGUAGE SQL;
+
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE OR REPLACE FUNCTION f(curs REFCURSOR) RETURNS INT AS $$
+  BEGIN
+    RETURN 0;
+  END
+$$ LANGUAGE PLpgSQL;
+
+# Function that references REFCURSOR internally.
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE OR REPLACE FUNCTION f() RETURNS INT AS $$
+  SELECT 'foo'::REFCURSOR;
+  SELECT 0;
+$$ LANGUAGE SQL;
+
+statement error pgcode 0A000 pq: refcursor not supported until version 23.2
+CREATE OR REPLACE FUNCTION f() RETURNS INT AS $$
+  BEGIN
+    SELECT 'foo'::REFCURSOR;
+    RETURN 0;
+  END
+$$ LANGUAGE PLpgSQL;

pkg/sql/logictest/testdata/logic_test/refcursor

@@ -0,0 +1,181 @@
+statement ok
+CREATE TABLE xy (x INT, y INT);
+
+# Cast to REFCURSOR.
+query T
+SELECT 'foo'::REFCURSOR;
+----
+foo
+
+# Cast to REFCURSOR using the vectorized engine.
+query T
+SELECT 'foo'::REFCURSOR FROM generate_series(1, 100) LIMIT 1;
+----
+foo
+
+# Table that references REFCURSOR.
+statement ok
+CREATE TABLE t (x REFCURSOR);
+
+# Add a REFCURSOR column.
+statement ok
+ALTER TABLE xy ADD COLUMN curs REFCURSOR;
+
+statement ok
+INSERT INTO xy VALUES (1, 2, 'foo');
+
+query IIT
+SELECT * FROM xy;
+----
+1  2  foo
+
+# Alter a column type to REFCURSOR.
+statement ok
+DROP TABLE IF EXISTS xy;
+CREATE TABLE xy (x INT, y INT);
+SET enable_experimental_alter_column_type_general=true;
+
+statement ok
+ALTER TABLE xy ALTER COLUMN y TYPE REFCURSOR;
+
+statement ok
+INSERT INTO xy VALUES (1, 'bar');
+
+query IT
+SELECT * FROM xy;
+----
+1  bar
+
+statement ok
+DROP TABLE IF EXISTS xy;
+CREATE TABLE xy (x INT, y INT);
+INSERT INTO xy VALUES (1, 2);
+INSERT INTO xy VALUES (3, 4);
+
+# Create a partial index that uses the REFCURSOR type.
+statement ok
+CREATE INDEX part ON xy (x) WHERE y::REFCURSOR < '3';
+
+query II
+SELECT * FROM xy@part WHERE y::REFCURSOR < '3';
+----
+1  2
+
+statement ok
+DROP TABLE IF EXISTS xy;
+CREATE TABLE xy (x INT, y INT);
+INSERT INTO xy VALUES (1, 2);
+
+# Add a check constraint that uses the REFCURSOR type.
+statement ok
+ALTER TABLE xy ADD CONSTRAINT bar CHECK (y::REFCURSOR < 'baz');
+
+query II
+SELECT * FROM xy;
+----
+1  2
+
+# UDT that references REFCURSOR.
+statement ok
+CREATE TYPE typ AS (x INT, y REFCURSOR);
+
+query T
+SELECT (100, 'bar')::typ;
+----
+(100,bar)
+
+# Function that returns REFCURSOR.
+statement ok
+CREATE FUNCTION f() RETURNS REFCURSOR AS $$
+  SELECT 'foo';
+$$ LANGUAGE SQL;
+
+query T
+SELECT f();
+----
+foo
+
+statement ok
+DROP FUNCTION f;
+
+statement ok
+CREATE FUNCTION f() RETURNS REFCURSOR AS $$
+  BEGIN
+    RETURN 'foo';
+  END
+$$ LANGUAGE PLpgSQL;
+
+query T
+SELECT f();
+----
+foo
+
+statement ok
+DROP FUNCTION f;
+
+# Function that takes REFCURSOR argument.
+statement ok
+CREATE FUNCTION f(curs REFCURSOR) RETURNS INT AS $$
+  SELECT 0;
+$$ LANGUAGE SQL;
+
+query I
+SELECT f('foo');
+----
+0
+
+statement ok
+DROP FUNCTION f;
+
+statement ok
+CREATE FUNCTION f(curs REFCURSOR) RETURNS INT AS $$
+  BEGIN
+    RETURN 0;
+  END
+$$ LANGUAGE PLpgSQL;
+
+query I
+SELECT f('foo');
+----
+0
+
+statement ok
+DROP FUNCTION f;
+
+# Function that references REFCURSOR internally.
+statement ok
+CREATE FUNCTION f() RETURNS INT AS $$
+  SELECT 'foo'::REFCURSOR;
+  SELECT 0;
+$$ LANGUAGE SQL;
+
+query I
+SELECT f();
+----
+0
+
+statement ok
+DROP FUNCTION f;
+
+statement ok
+CREATE FUNCTION f() RETURNS INT AS $$
+  BEGIN
+    SELECT 'foo'::REFCURSOR;
+    RETURN 0;
+  END
+$$ LANGUAGE PLpgSQL;
+
+query I
+SELECT f();
+----
+0
+
+# TODO(drewk): REFCURSOR should not support collation.
+query T
+SELECT 'foo'::REFCURSOR COLLATE en;
+----
+foo
+
+# REFCURSOR does not have a width.
+statement error pgcode 42601 syntax error
+SELECT 'foo'::REFCURSOR(2);

pkg/sql/logictest/tests/cockroach-go-testserver-upgrade-to-master/BUILD.bazel

@@ -15,7 +15,7 @@ go_test(
         "//pkg/sql/logictest:testdata",  # keep
     ],
     exec_properties = {"Pool": "large"},
-    shard_count = 12,
+    shard_count = 13,
     tags = [
         "cpu:2",
     ],