sql: sql parser for CREATE FUNCTION statement

This commit added parser support for `CREATE FUNCTION` sql
statement. Scanner was extended so that it can recognize the
`BEGIN ATOMIC` context so that it doesnot return early when it
sees `;` charater which normally indicates the end of a
statement.

Release note (sql change): `CREATE FUNCTION` statement now
can be parsed by crdb, but an unimplemented error would be
thrown since the statement processing is not done yet.

docs/generated/sql/bnf/BUILD.bazel

@@ -74,6 +74,7 @@ FILES = [
     "create_database_stmt",
     "create_ddl_stmt",
     "create_extension_stmt",
+    "create_func_stmt",
     "create_index_stmt",
     "create_inverted_index_stmt",
     "create_role_stmt",
@@ -126,6 +127,9 @@ FILES = [
     "insert_stmt",
     "iso_level",
     "joined_table",
+    "legacy_begin_stmt",
+    "legacy_end_stmt",
+    "legacy_transaction_stmt",
     "like_table_option_list",
     "limit_clause",
     "move_cursor_stmt",
@@ -163,6 +167,8 @@ FILES = [
     "resume_stmt",
     "revoke_stmt",
     "rollback_transaction",
+    "routine_body_stmt",
+    "routine_return_stmt",
     "row_source_extension_stmt",
     "savepoint_stmt",
     "scrub_database_stmt",
@@ -226,6 +232,7 @@ FILES = [
     "split_table_at",
     "stmt",
     "stmt_block",
+    "stmt_without_legacy_transaction",
     "table_clause",
     "table_constraint",
     "table_ref",

docs/generated/sql/bnf/begin_stmt.bnf

@@ -1,19 +1 @@
 begin_stmt ::=
-	'BEGIN' 'TRANSACTION' 'PRIORITY' 'LOW' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN' 'TRANSACTION' 'PRIORITY' 'NORMAL' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN' 'TRANSACTION' 'PRIORITY' 'HIGH' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN' 'TRANSACTION' 'READ' 'ONLY' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN' 'TRANSACTION' 'READ' 'WRITE' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN' 'TRANSACTION' 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN' 'TRANSACTION' 'DEFERRABLE' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN' 'TRANSACTION' 'NOT' 'DEFERRABLE' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN' 'TRANSACTION' 
-	| 'BEGIN'  'PRIORITY' 'LOW' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN'  'PRIORITY' 'NORMAL' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN'  'PRIORITY' 'HIGH' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN'  'READ' 'ONLY' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN'  'READ' 'WRITE' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN'  'AS' 'OF' 'SYSTEM' 'TIME' a_expr ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN'  'DEFERRABLE' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN'  'NOT' 'DEFERRABLE' ( ( ( ',' |  ) ( ( 'PRIORITY' ( 'LOW' | 'NORMAL' | 'HIGH' ) ) | ( 'READ' 'ONLY' | 'READ' 'WRITE' ) | ( 'AS' 'OF' 'SYSTEM' 'TIME' a_expr ) | ( 'DEFERRABLE' | 'NOT' 'DEFERRABLE' ) ) ) )*
-	| 'BEGIN'  

docs/generated/sql/bnf/commit_transaction.bnf

@@ -1,5 +1,3 @@
 commit_stmt ::=
 	'COMMIT' 'TRANSACTION'
 	| 'COMMIT' 
-	| 'END' 'TRANSACTION'
-	| 'END' 

docs/generated/sql/bnf/create_ddl_stmt.bnf

@@ -7,3 +7,4 @@ create_ddl_stmt ::=
 	| create_type_stmt
 	| create_view_stmt
 	| create_sequence_stmt
+	| create_func_stmt

docs/generated/sql/bnf/create_func_stmt.bnf

@@ -0,0 +1,2 @@
+create_func_stmt ::=
+	'CREATE' opt_or_replace 'FUNCTION' func_create_name '(' opt_func_arg_with_default_list ')' 'RETURNS' opt_return_set func_return_type opt_create_func_opt_list opt_routine_body

docs/generated/sql/bnf/legacy_begin_stmt.bnf

@@ -0,0 +1,2 @@
+legacy_begin_stmt ::=
+	'BEGIN' opt_transaction begin_transaction

docs/generated/sql/bnf/legacy_end_stmt.bnf

@@ -0,0 +1,2 @@
+legacy_end_stmt ::=
+	'END' opt_transaction

docs/generated/sql/bnf/legacy_transaction_stmt.bnf

@@ -0,0 +1,3 @@
+legacy_transaction_stmt ::=
+	legacy_begin_stmt
+	| legacy_end_stmt

docs/generated/sql/bnf/routine_body_stmt.bnf

@@ -0,0 +1,3 @@
+routine_body_stmt ::=
+	stmt_without_legacy_transaction
+	| routine_return_stmt

docs/generated/sql/bnf/routine_return_stmt.bnf

@@ -0,0 +1,2 @@
+routine_return_stmt ::=
+	'RETURN' a_expr

docs/generated/sql/bnf/stmt.bnf

@@ -1,23 +1,4 @@
 stmt ::=
 	'HELPTOKEN'
-	| preparable_stmt
-	| analyze_stmt
-	| copy_from_stmt
-	| comment_stmt
-	| execute_stmt
-	| deallocate_stmt
-	| discard_stmt
-	| grant_stmt
-	| prepare_stmt
-	| revoke_stmt
-	| savepoint_stmt
-	| reassign_owned_by_stmt
-	| drop_owned_by_stmt
-	| release_stmt
-	| refresh_stmt
-	| nonpreparable_set_stmt
-	| transaction_stmt
-	| close_cursor_stmt
-	| declare_cursor_stmt
-	| fetch_cursor_stmt
-	| move_cursor_stmt
+	| stmt_without_legacy_transaction
+	| legacy_transaction_stmt