sql: add TRIGGER datatype

This patch adds support for the special datatype `TRIGGER`. It is only
used as the return type of a trigger function, and leads to an error in
other contexts. This patch does not add support for trigger functions,
tracked in cockroachdb#126356.

Fixes cockroachdb#126476

Release note: None

pkg/ccl/logictestccl/testdata/logic_test/triggers

@@ -0,0 +1,164 @@
+# TODO(#126356): remove this case when trigger functions are supported.
+statement error pgcode 0A000 pq: unimplemented: trigger functions are not yet supported
+CREATE FUNCTION f() RETURNS TRIGGER LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL; END $$;
+
+# ==============================================================================
+# Trigger functions cannot be directly invoked.
+# ==============================================================================
+
+subtest direct_invocation
+
+# TODO(#126356): uncomment these cases when trigger functions are supported.
+#statement ok
+#CREATE FUNCTION f() RETURNS TRIGGER LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL; END $$;
+#
+#statement error pgcode 0A000 pq: trigger functions can only be called as triggers
+#SELECT f();
+#
+#statement error pgcode 0A000 pq: trigger functions can only be called as triggers
+#CREATE FUNCTION foo() RETURNS INT LANGUAGE SQL AS $$ SELECT f(); SELECT 1; $$;
+#
+#statement error pgcode 0A000 pq: trigger functions can only be called as triggers
+#CREATE FUNCTION foo() RETURNS INT LANGUAGE PLpgSQL AS $$ BEGIN SELECT f(); RETURN 1; END $$;
+#
+#statement ok
+#DROP FUNCTION f;
+
+# ==============================================================================
+# Test invalid usage of parameters in trigger functions.
+# ==============================================================================
+
+# Trigger functions are not allowed to be defined with parameters. Instead,
+# arguments are passed through the implicitly defined TG_ARGV variable.
+subtest parameters
+
+statement error pgcode 42P13 pq: trigger functions cannot have declared arguments
+CREATE FUNCTION f(x TEXT) RETURNS TRIGGER LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL; END $$;
+
+statement error pgcode 42P13 pq: function result type must be string because of OUT parameters
+CREATE FUNCTION f(OUT x TEXT) RETURNS TRIGGER LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL; END $$;
+
+statement error pgcode 42P13 pq: function result type must be string because of OUT parameters
+CREATE FUNCTION f(INOUT x TEXT) RETURNS TRIGGER LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL; END $$;
+
+# ==============================================================================
+# Test invalid usage of the TRIGGER datatype in PL/pgSQL routines.
+# ==============================================================================
+
+subtest trigger_in_plpgsql_routine
+
+statement error pgcode 0A000 pq: cannot accept a value of type trigger
+CREATE FUNCTION f() RETURNS RECORD LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL::TRIGGER; END $$;
+
+statement error pgcode 0A000 pq: PL/pgSQL functions cannot accept type trigger
+CREATE FUNCTION f(x TRIGGER) RETURNS INT LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL; END $$;
+
+statement error pgcode 0A000 pq: PL/pgSQL functions cannot accept type trigger
+CREATE FUNCTION f(OUT x TRIGGER) LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL; END $$;
+
+statement error pgcode 0A000 pq: PL/pgSQL functions cannot accept type trigger
+CREATE FUNCTION f(INOUT x TRIGGER) RETURNS INT LANGUAGE PLpgSQL AS $$ BEGIN RETURN NULL; END $$;
+
+statement error pgcode 0A000 pq: PL/pgSQL functions cannot accept type trigger
+CREATE PROCEDURE p(x TRIGGER) LANGUAGE PLpgSQL AS $$ BEGIN END $$;
+
+statement error pgcode 0A000 pq: PL/pgSQL functions cannot accept type trigger
+CREATE PROCEDURE p(OUT x TRIGGER) LANGUAGE PLpgSQL AS $$ BEGIN END $$;
+
+statement error pgcode 0A000 pq: PL/pgSQL functions cannot accept type trigger
+CREATE PROCEDURE p(INOUT x TRIGGER) LANGUAGE PLpgSQL AS $$ BEGIN END $$;
+
+# ==============================================================================
+# Test invalid usage of the TRIGGER datatype in SQL routines.
+# ==============================================================================
+
+subtest trigger_in_sql_routine
+
+statement error pgcode 0A000 pq: cannot accept a value of type trigger
+CREATE FUNCTION f() RETURNS RECORD LANGUAGE SQL AS $$ SELECT NULL::TRIGGER; $$;
+
+statement error pgcode 42P13 pq: SQL functions cannot return type trigger
+CREATE FUNCTION f() RETURNS TRIGGER LANGUAGE SQL AS $$ SELECT NULL $$;
+
+statement error pgcode 42P13 pq: SQL functions cannot have arguments of type trigger
+CREATE FUNCTION f(x TRIGGER) RETURNS INT LANGUAGE SQL AS $$ SELECT NULL $$;
+
+statement error pgcode 42P13 pq: SQL functions cannot return type trigger
+CREATE FUNCTION f(OUT x TRIGGER) LANGUAGE SQL AS $$ SELECT NULL $$;
+
+statement error pgcode 42P13 pq: SQL functions cannot return type trigger
+CREATE FUNCTION f(INOUT x TRIGGER) RETURNS INT LANGUAGE SQL AS $$ SELECT NULL $$;
+
+statement error pgcode 42P13 pq: SQL functions cannot have arguments of type trigger
+CREATE PROCEDURE p(x TRIGGER) LANGUAGE SQL AS $$ SELECT NULL $$;
+
+statement error pgcode 42P13 pq: SQL functions cannot return type trigger
+CREATE PROCEDURE p(OUT x TRIGGER) LANGUAGE SQL AS $$ SELECT NULL $$;
+
+statement error pgcode 42P13 pq: SQL functions cannot return type trigger
+CREATE PROCEDURE p(INOUT x TRIGGER) LANGUAGE SQL AS $$ SELECT NULL $$;
+
+# ==============================================================================
+# Test invalid usage of the TRIGGER datatype in SQL statements.
+# ==============================================================================
+
+subtest trigger_in_sql_statement
+
+# Cast.
+statement error pgcode 0A000 pq: cannot accept a value of type trigger
+SELECT NULL::TRIGGER;
+
+# Trigger array cast.
+statement error pgcode 42704 pq: at or near "EOF": syntax error: type trigger\[\] does not exist
+SELECT NULL::TRIGGER[];
+
+# Invalid cast from integer.
+statement error pgcode 42846 pq: invalid cast: int -> trigger
+SELECT 1::TRIGGER;
+
+# Type annotation.
+statement error pgcode 0A000 pq: cannot accept a value of type trigger
+SELECT NULL:::TRIGGER;
+
+# Builtin type conversion function.
+statement error pgcode 0A000 pq: cannot accept a value of type trigger
+SELECT triggerin(1);
+
+# Builtin type conversion function with NULL argument.
+# NOTE: this case succeeds because the function is not actually called
+# or fully type-checked when it is supplied NULL arguments.
+# statement error pgcode 0A000 pq: cannot accept a value of type trigger
+statement ok
+SELECT triggerin(NULL);
+
+# ==============================================================================
+# Test invalid usage of the TRIGGER datatype in CREATE statements.
+# ==============================================================================
+
+subtest trigger_in_create
+
+# Column type.
+statement error pgcode 42P16 pq: value type trigger cannot be used for table columns
+CREATE TABLE t (x INT, y TRIGGER, z TEXT);
+
+# Array column type.
+statement error pgcode 42704 pq: at or near ",": syntax error: type trigger\[\] does not exist
+CREATE TABLE t (x INT, y TRIGGER[], z TEXT);
+
+# Cast in partial index predicate.
+statement error pgcode 0A000 pq: cannot accept a value of type trigger
+CREATE TABLE t (x INT, y INT, INDEX (y) WHERE (NULL::TRIGGER IS NOT NULL));
+
+# Cast in computed column expression.
+statement error pgcode 0A000 pq: cannot accept a value of type trigger
+CREATE TABLE t (x INT, y BOOL GENERATED ALWAYS AS (NULL::TRIGGER IS NOT NULL) STORED);
+
+# Trigger UDT field.
+statement error pgcode 0A000 pq: cannot accept a value of type trigger
+CREATE TYPE udt AS (x INT, y TRIGGER, z TEXT);
+
+# Trigger array UDT field.
+statement error pgcode 42601 pq: at or near "\[": syntax error
+CREATE TYPE udt AS (x INT, y TRIGGER[], z TEXT);
+
+subtest end

pkg/ccl/logictestccl/tests/fakedist-disk/BUILD.bazel

@@ -12,7 +12,7 @@ go_test(
         "//build/toolchains:is_heavy": {"test.Pool": "heavy"},
         "//conditions:default": {"test.Pool": "large"},
     }),
-    shard_count = 29,
+    shard_count = 30,
     tags = ["cpu:2"],
     deps = [
         "//pkg/base",

pkg/ccl/logictestccl/tests/fakedist-vec-off/BUILD.bazel

@@ -12,7 +12,7 @@ go_test(
         "//build/toolchains:is_heavy": {"test.Pool": "heavy"},
         "//conditions:default": {"test.Pool": "large"},
     }),
-    shard_count = 29,
+    shard_count = 30,
     tags = ["cpu:2"],
     deps = [
         "//pkg/base",

pkg/ccl/logictestccl/tests/fakedist/BUILD.bazel

@@ -12,7 +12,7 @@ go_test(
         "//build/toolchains:is_heavy": {"test.Pool": "heavy"},
         "//conditions:default": {"test.Pool": "large"},
     }),
-    shard_count = 30,
+    shard_count = 31,
     tags = ["cpu:2"],
     deps = [
         "//pkg/base",

pkg/ccl/logictestccl/tests/local-legacy-schema-changer/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
         "//pkg/ccl/logictestccl:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 29,
+    shard_count = 30,
     tags = ["cpu:1"],
     deps = [
         "//pkg/base",

pkg/ccl/logictestccl/tests/local-mixed-23.2/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
         "//pkg/ccl/logictestccl:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 25,
+    shard_count = 26,
     tags = ["cpu:1"],
     deps = [
         "//pkg/base",

pkg/ccl/logictestccl/tests/local-read-committed/BUILD.bazel

@@ -10,7 +10,7 @@ go_test(
         "//pkg/sql/opt/exec/execbuilder:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 36,
+    shard_count = 37,
     tags = ["cpu:1"],
     deps = [
         "//pkg/base",

pkg/ccl/logictestccl/tests/local-vec-off/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
         "//pkg/ccl/logictestccl:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 29,
+    shard_count = 30,
     tags = ["cpu:1"],
     deps = [
         "//pkg/base",

pkg/ccl/logictestccl/tests/local/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
         "//pkg/ccl/logictestccl:testdata",  # keep
     ],
     exec_properties = {"test.Pool": "large"},
-    shard_count = 46,
+    shard_count = 47,
     tags = ["cpu:1"],
     deps = [
         "//pkg/base",

pkg/sql/create_type.go

@@ -418,8 +418,10 @@ func createCompositeTypeDesc(
 		if err != nil {
 			return nil, err
 		}
-		err = tree.CheckUnsupportedType(params.ctx, &params.p.semaCtx, typ)
-		if err != nil {
+		if typ.Identical(types.Trigger) {
+			return nil, tree.CannotAcceptTriggerErr
+		}
+		if err = tree.CheckUnsupportedType(params.ctx, &params.p.semaCtx, typ); err != nil {
 			return nil, err
 		}
 		if typ.UserDefined() {

pkg/sql/exec_util.go

@@ -2070,6 +2070,10 @@ func checkResultType(typ *types.T, fmtCode pgwirebase.FormatCode) error {
 	case types.AnyFamily:
 		// Placeholder case.
 		return errors.Errorf("could not determine data type of %s", typ)
+	case types.TriggerFamily:
+		// The TRIGGER datatype is only allowed as the return type of a trigger
+		// function.
+		return tree.CannotAcceptTriggerErr
 	default:
 		return errors.Errorf("unsupported result type: %s", typ)
 	}