sql: implement function OID reference

This commit implements `[FUNCTION xxxx]` OID references syntax
of functions. With this change, functions can be called with
the new OID numerical representation. For example
`SELECT [FUNCTION 123]('helloworld')`. The intention of this
syntax is only for internal serialization of references to UDFs.
But it's general enough for builtin functions as well.

A new implementation of the `ResolvableFunctionReference`
interface, `OIDFunctionReference` is introduced for function
resolution purpose for the new syntax.

The `ResolveFunctionByOID` method is also refactored to return
a qualified name.

Fixes: #83231

Release note: None

docs/generated/sql/bnf/stmt_block.bnf

@@ -3495,11 +3495,11 @@ opt_interval_qualifier ::=
 	| 
 
 func_application ::=
-	func_name '(' ')'
-	| func_name '(' expr_list opt_sort_clause ')'
-	| func_name '(' 'ALL' expr_list opt_sort_clause ')'
-	| func_name '(' 'DISTINCT' expr_list ')'
-	| func_name '(' '*' ')'
+	func_application_name '(' ')'
+	| func_application_name '(' expr_list opt_sort_clause ')'
+	| func_application_name '(' 'ALL' expr_list opt_sort_clause ')'
+	| func_application_name '(' 'DISTINCT' expr_list ')'
+	| func_application_name '(' '*' ')'
 
 within_group_clause ::=
 	'WITHIN' 'GROUP' '(' single_sort_clause ')'
@@ -3751,10 +3751,9 @@ rowsfrom_item ::=
 opt_col_def_list ::=
 	'(' col_def_list ')'
 
-func_name ::=
-	type_function_name
-	| prefixed_column_path
-	| 'INDEX'
+func_application_name ::=
+	func_name
+	| '[' 'FUNCTION' iconst32 ']'
 
 single_sort_clause ::=
 	'ORDER' 'BY' sortby
@@ -3902,10 +3901,10 @@ create_as_params ::=
 col_def_list ::=
 	( col_def ) ( ( ',' col_def ) )*
 
-type_function_name ::=
-	'identifier'
-	| unreserved_keyword
-	| type_func_name_keyword
+func_name ::=
+	type_function_name
+	| prefixed_column_path
+	| 'INDEX'
 
 opt_existing_window_name ::=
 	name
@@ -3946,6 +3945,11 @@ trim_list ::=
 	| 'FROM' expr_list
 	| expr_list
 
+type_function_name ::=
+	'identifier'
+	| unreserved_keyword
+	| type_func_name_keyword
+
 char_aliases ::=
 	'CHAR'
 	| 'CHARACTER'

pkg/ccl/changefeedccl/cdceval/func_resolver.go

@@ -88,13 +88,13 @@ func (rs *cdcFunctionResolver) ResolveFunction(
 // ResolveFunctionByOID implements FunctionReferenceResolver interface.
 func (rs *cdcFunctionResolver) ResolveFunctionByOID(
 	ctx context.Context, oid oid.Oid,
-) (string, *tree.Overload, error) {
+) (*tree.FunctionName, *tree.Overload, error) {
 	fnName, overload, err := rs.wrapped.ResolveFunctionByOID(ctx, oid)
 	if err != nil {
-		return "", nil, err
+		return nil, nil, err
 	}
-	if err := checkOverloadSupported(fnName, overload); err != nil {
-		return "", nil, err
+	if err := checkOverloadSupported(fnName.Object(), overload); err != nil {
+		return nil, nil, err
 	}
 	return fnName, overload, err
 }

pkg/sql/faketreeeval/evalctx.go

@@ -453,8 +453,8 @@ func (ep *DummyEvalPlanner) ResolveFunction(
 // ResolveFunctionByOID implements FunctionReferenceResolver interface.
 func (ep *DummyEvalPlanner) ResolveFunctionByOID(
 	ctx context.Context, oid oid.Oid,
-) (string, *tree.Overload, error) {
-	return "", nil, errors.AssertionFailedf("ResolveFunctionByOID unimplemented")
+) (*tree.FunctionName, *tree.Overload, error) {
+	return nil, nil, errors.AssertionFailedf("ResolveFunctionByOID unimplemented")
 }
 
 // GetMultiregionConfig is part of the eval.Planner interface.

pkg/sql/importer/import_table_creation.go

@@ -431,6 +431,6 @@ func (r fkResolver) ResolveFunction(
 // ResolveFunctionByOID implements the resolver.SchemaResolver interface.
 func (r fkResolver) ResolveFunctionByOID(
 	ctx context.Context, oid oid.Oid,
-) (string, *tree.Overload, error) {
-	return "", nil, errSchemaResolver
+) (*tree.FunctionName, *tree.Overload, error) {
+	return nil, nil, errSchemaResolver
 }

pkg/sql/logictest/testdata/logic_test/udf_oid_ref

@@ -0,0 +1,134 @@
+# 1074 is the OID of builtin function "string_to_array" with signature
+# "string_to_array(str: string, delimiter: string) -> string[]".
+query T
+SELECT [FUNCTION 1074]('hello,world', ',')
+----
+{hello,world}
+
+statement ok
+CREATE TABLE t1(a INT PRIMARY KEY, b STRING DEFAULT ([FUNCTION 1074]('hello,world', ',')))
+
+statement ok
+INSERT INTO t1(a) VALUES (1)
+
+query IT
+SELECT * FROM t1
+----
+1  {hello,world}
+
+statement ok
+INSERT INTO t1 VALUES (2, 'hello,new,world')
+
+statement ok
+CREATE INDEX idx ON t1([FUNCTION 1074](b,','))
+
+query IT
+SELECT * FROM t1@idx WHERE [FUNCTION 1074](b, ',') = ARRAY['hello','new','world']
+----
+2  hello,new,world
+
+# 814 is the OID of builtin function "length" with signature
+# "length(val: string) -> int".
+statement ok
+ALTER TABLE t1 ADD CONSTRAINT c_len CHECK ([FUNCTION 814](b) > 2)
+
+statement error pq: failed to satisfy CHECK constraint \(length\(b\) > 2:::INT8\)
+INSERT INTO t1 VALUES (3, 'a')
+
+statement ok
+CREATE FUNCTION f1() RETURNS INT LANGUAGE SQL AS $$ SELECT 1 $$
+
+let $fn_oid
+SELECT oid FROM pg_catalog.pg_proc WHERE proname = 'f1'
+
+query I
+SELECT [FUNCTION $fn_oid]()
+----
+1
+
+statement ok
+CREATE FUNCTION f2(a STRING) RETURNS STRING LANGUAGE SQL AS $$ SELECT a $$
+
+let $fn_oid
+SELECT oid FROM pg_catalog.pg_proc WHERE proname = 'f2'
+
+query T
+SELECT [FUNCTION $fn_oid]('hello world')
+----
+hello world
+
+# Make sure that argument types are still checked even we know which function
+# overload to use.
+statement error pq: unknown signature: f2\(int\)
+SELECT [FUNCTION $fn_oid](123)
+
+# Make sure that renaming does not break the reference.
+statement ok
+ALTER FUNCTION f2(STRING) RENAME TO f2_new;
+
+query T
+SELECT [FUNCTION $fn_oid]('hello world')
+----
+hello world
+
+statement ok
+CREATE SCHEMA sc1;
+
+statement ok
+ALTER FUNCTION f2_new(STRING) SET SCHEMA sc1;
+
+query T
+SELECT [FUNCTION $fn_oid]('hello world')
+----
+hello world
+
+# Make sure that function dropped cannot be resolved.
+statement ok
+DROP FUNCTION sc1.f2_new(STRING);
+
+statement error function undefined
+SELECT [FUNCTION $fn_oid]('maybe')
+
+# Referencing UDF OID within a UDF
+
+statement ok
+CREATE FUNCTION f_in_udf() RETURNS INT LANGUAGE SQL AS $$ SELECT 1 $$;
+
+let $fn_oid
+SELECT oid FROM pg_catalog.pg_proc WHERE proname = 'f_in_udf'
+
+# TODO(chengxiong,mgartner): Fix this test when we enable support of calling UDFs from UDFs.
+statement error pq: function \d+ not found: function undefined
+CREATE FUNCTION f_using_udf() RETURNS INT LANGUAGE SQL AS $$ SELECT [FUNCTION $fn_oid]() $$;
+
+# 814 is the OID of builtin function "length" with signature, and it's ok to
+# call it from a UDF.
+statement ok
+CREATE FUNCTION f_using_udf() RETURNS INT LANGUAGE SQL AS $$ SELECT [FUNCTION 814]('abc') $$;
+
+query I
+SELECT f_using_udf();
+----
+3
+
+# Make sure cross-db reference by OID is ok
+
+statement ok
+CREATE DATABASE db1
+
+statement ok
+USE db1
+
+statement ok
+CREATE FUNCTION f_cross_db() RETURNS INT LANGUAGE SQL AS $$ SELECT 321 $$;
+
+let $fn_oid
+SELECT oid FROM pg_catalog.pg_proc WHERE proname = 'f_cross_db'
+
+statement ok
+USE test
+
+query I
+SELECT [FUNCTION $fn_oid]()
+----
+321

pkg/sql/opt/cat/catalog.go

@@ -155,7 +155,7 @@ type Catalog interface {
 	) (*tree.ResolvedFunctionDefinition, error)
 
 	// ResolveFunctionByOID resolves a function overload by OID.
-	ResolveFunctionByOID(ctx context.Context, oid oid.Oid) (string, *tree.Overload, error)
+	ResolveFunctionByOID(ctx context.Context, oid oid.Oid) (*tree.FunctionName, *tree.Overload, error)
 
 	// CheckPrivilege verifies that the current user has the given privilege on
 	// the given catalog object. If not, then CheckPrivilege returns an error.

pkg/sql/opt/testutils/testcat/function.go

@@ -51,8 +51,8 @@ func (tc *Catalog) ResolveFunction(
 // ResolveFunctionByOID part of the tree.FunctionReferenceResolver interface.
 func (tc *Catalog) ResolveFunctionByOID(
 	ctx context.Context, oid oid.Oid,
-) (string, *tree.Overload, error) {
-	return "", nil, errors.AssertionFailedf("ResolveFunctionByOID not supported in test catalog")
+) (*tree.FunctionName, *tree.Overload, error) {
+	return nil, nil, errors.AssertionFailedf("ResolveFunctionByOID not supported in test catalog")
 }
 
 // CreateFunction handles the CREATE FUNCTION statement.

pkg/sql/opt_catalog.go

@@ -344,7 +344,7 @@ func (oc *optCatalog) ResolveFunction(
 
 func (oc *optCatalog) ResolveFunctionByOID(
 	ctx context.Context, oid oid.Oid,
-) (string, *tree.Overload, error) {
+) (*tree.FunctionName, *tree.Overload, error) {
 	return oc.planner.ResolveFunctionByOID(ctx, oid)
 }