[REVIEW] Modified show.ftl to conditionally expect FROM in parsing logic

dask_sql/physical/rel/custom/tables.py

@@ -29,7 +29,12 @@ class ShowTablesPlugin(BaseRelPlugin):
     def convert(
         self, sql: "org.apache.calcite.sql.SqlNode", context: "dask_sql.Context"
     ) -> DataContainer:
-        schema = str(sql.getSchema()).split(".")[-1]
+        schema = sql.getSchema()
+        if schema is not None:
+            schema = str(schema).split(".")[-1]
+        else:
+            schema = context.DEFAULT_SCHEMA_NAME
+
         if schema not in context.schema:
             raise AttributeError(f"Schema {schema} is not defined.")
 

planner/src/main/codegen/includes/show.ftl

@@ -22,11 +22,13 @@ SqlNode SqlShowSchemas() :
 SqlNode SqlShowTables() :
 {
    final Span s;
-   final SqlIdentifier schema;
+   SqlIdentifier schema = null;
 }
 {
-    <SHOW> { s = span(); } <TABLES> <FROM>
-    schema = SimpleIdentifier()
+    <SHOW> { s = span(); } <TABLES>
+    (
+            <FROM> schema = SimpleIdentifier()
+    )?
     {
         return new SqlShowTables(s.end(this), schema);
     }

planner/src/main/java/com/dask/sql/parser/SqlShowTables.java

@@ -7,6 +7,7 @@
 import org.apache.calcite.sql.parser.SqlParserPos;
 
 public class SqlShowTables extends SqlDescribeSchema {
+
     public SqlShowTables(SqlParserPos pos, SqlIdentifier schemaName) {
         super(pos, schemaName);
     }
@@ -15,6 +16,8 @@ public SqlShowTables(SqlParserPos pos, SqlIdentifier schemaName) {
     public void unparse(SqlWriter writer, int leftPrec, int rightPrec) {
         writer.keyword("SHOW");
         writer.keyword("TABLES");
-        this.getSchema().unparse(writer, leftPrec, rightPrec);
+        if (this.getSchema() != null) {
+            this.getSchema().unparse(writer, leftPrec, rightPrec);
+        }
     }
 }

tests/integration/test_show.py

@@ -2,6 +2,8 @@
 import pytest
 from pandas.testing import assert_frame_equal
 
+from dask_sql import Context
+
 try:
     import cudf
 except ImportError:
@@ -95,3 +97,14 @@ def test_wrong_input(c):
         c.sql(f'SHOW COLUMNS FROM "{c.schema_name}"."table"')
     with pytest.raises(AttributeError):
         c.sql('SHOW TABLES FROM "wrong"')
+
+
+def test_show_tables_no_schema(c):
+    c = Context()
+
+    df = pd.DataFrame({"id": [0, 1]})
+    c.create_table("test", df)
+
+    actual_df = c.sql("show tables").compute()
+    expected_df = pd.DataFrame({"Table": ["test"]})
+    assert_frame_equal(actual_df, expected_df)