fix: support SHOW (ALL) TABLES for duckdb (#4961)

* fix: support SHOW (ALL) TABLES for duckdb

* Fix styling

* Fix set difference

* Fix styling

* Preserve ALL prefix

* Fix test

* Fix formatting

---------

Co-authored-by: Jo <46752250+georgesittas@users.noreply.github.com>

Author: mscolnick

sqlglot/dialects/duckdb.py

@@ -156,6 +156,13 @@ def _build_make_timestamp(args: t.List) -> exp.Expression:
     )
 
 
+def _show_parser(*args: t.Any, **kwargs: t.Any) -> t.Callable[[DuckDB.Parser], exp.Show]:
+    def _parse(self: DuckDB.Parser) -> exp.Show:
+        return self._parse_show_duckdb(*args, **kwargs)
+
+    return _parse
+
+
 def _struct_sql(self: DuckDB.Generator, expression: exp.Struct) -> str:
     args: t.List[str] = []
 
@@ -348,6 +355,8 @@ class Tokenizer(tokens.Tokenizer):
             "$": TokenType.PARAMETER,
         }
 
+        COMMANDS = tokens.Tokenizer.COMMANDS - {TokenType.SHOW}
+
     class Parser(parser.Parser):
         BITWISE = {
             **parser.Parser.BITWISE,
@@ -369,6 +378,11 @@ class Parser(parser.Parser):
 
         FUNCTIONS_WITH_ALIASED_ARGS = {*parser.Parser.FUNCTIONS_WITH_ALIASED_ARGS, "STRUCT_PACK"}
 
+        SHOW_PARSERS = {
+            "TABLES": _show_parser("TABLES"),
+            "ALL TABLES": _show_parser("ALL TABLES"),
+        }
+
         FUNCTIONS = {
             **parser.Parser.FUNCTIONS,
             "ARRAY_REVERSE_SORT": _build_sort_array_desc,
@@ -467,6 +481,7 @@ class Parser(parser.Parser):
             **parser.Parser.STATEMENT_PARSERS,
             TokenType.ATTACH: lambda self: self._parse_attach_detach(),
             TokenType.DETACH: lambda self: self._parse_attach_detach(is_attach=False),
+            TokenType.SHOW: lambda self: self._parse_show(),
         }
 
         def _parse_expression(self) -> t.Optional[exp.Expression]:
@@ -581,6 +596,9 @@ def _parse_attach_option() -> exp.AttachOption:
                 else self.expression(exp.Detach, this=this, exists=exists)
             )
 
+        def _parse_show_duckdb(self, this: str) -> exp.Show:
+            return self.expression(exp.Show, this=this)
+
     class Generator(generator.Generator):
         PARAMETER_TOKEN = "$"
         NAMED_PLACEHOLDER_TOKEN = "$"

tests/dialects/test_duckdb.py

@@ -1598,3 +1598,7 @@ def test_at_sign_to_abs(self):
             "SELECT (@-1) + 1",
             "SELECT (ABS(-1)) + 1",
         )
+
+    def test_show_tables(self):
+        self.validate_identity("SHOW TABLES").assert_is(exp.Show)
+        self.validate_identity("SHOW ALL TABLES").assert_is(exp.Show)