Merge pull request #446 from mabel-dev/FEATURE/#351

Feature/#351 Support `SHOW FUNCTIONS`

docs/Release Notes/Change Log.md

@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 - [[#366](https://github.com/mabel-dev/opteryx/issues/336)] Implement 'function not found' suggestions. ([@joocer](https://github.com/joocer))   
 - [[#443](https://github.com/mabel-dev/opteryx/issues/443)] Introduce a CLI. ([@joocer](https://github.com/joocer))  
+- [[#351](https://github.com/mabel-dev/opteryx/issues/351)] Support `SHOW FUNCTIONS`. ([@joocer](https://github.com/joocer))  
 
 **Changed**
 

docs/SQL Reference/02 Statements.md

@@ -139,10 +139,10 @@ LIMIT count
 List the columns in a relation along with their data type. Without any modifiers, `SHOW COLUMNS` only reads a single page of data before returning.
 
 ~~~sql
- SHOW [EXTENDED] [FULL] COLUMNS
- FROM relation
- LIKE pattern
-  FOR period
+SHOW [EXTENDED] [FULL] COLUMNS
+FROM relation
+LIKE pattern
+ FOR period
 ~~~
 
 ### EXTENDED modifier
@@ -175,4 +175,12 @@ FOR DATES IN range
 
 The `FOR` clause specifies the date to review data for. Although this supports the full syntax as per the `SELECT` statements.
 
-See [Temporality](https://mabel-dev.github.io/opteryx/SQL%20Reference/09%20Temporality/) for more information on `FOR` syntax and functionality.
+See [Temporality](https://mabel-dev.github.io/opteryx/SQL%20Reference/09%20Temporality/) for more information on `FOR` syntax and functionality.
+
+## SHOW FUNCTIONS
+
+List the functions and aggregators supported by the engine.
+
+~~~sql
+SHOW FUNCTIONS
+~~~

opteryx/managers/query/planner/planner.py

@@ -118,6 +118,8 @@ def create_plan(self, sql: str = None, ast: dict = None):
             self._explain_planner(self._ast, self._statistics)
         elif "ShowColumns" in self._ast[0]:
             self._show_columns_planner(self._ast, self._statistics)
+        elif "ShowVariable" in self._ast[0]:
+            self._show_variable_planner(self._ast, self._statistics)
         else:  # pragma: no cover
             raise SqlError("Unknown or unsupported Query type.")
 
@@ -720,6 +722,40 @@ def _extract_identifiers(self, ast):
 
         return list(set(identifiers))
 
+    def _show_variable_planner(self, ast, statistics):
+        """
+        SHOW <variable> only really has a single node.
+
+        All of the keywords should up as a 'values' list in the variable in the ast.
+
+        The last word is the variable, preceeding words are modifiers.
+        """
+
+        directives = self._extract_directives(ast)
+
+        keywords = [
+            value["value"].upper() for value in ast[0]["ShowVariable"]["variable"]
+        ]
+        if keywords[-1] == "FUNCTIONS":
+            show_node = "show_functions"
+            node = operators.ShowFunctionsNode(
+                directives=directives,
+                statistics=statistics,
+            )
+            self.add_operator(show_node, operator=node)
+        else:  # pragma: no cover
+            raise SqlError(f"SHOW statement type not supported for `{keywords[-1]}`.")
+
+        name_column = ExpressionTreeNode(NodeType.IDENTIFIER, value="name")
+
+        order_by_node = operators.SortNode(
+            directives=directives,
+            statistics=statistics,
+            order=[([name_column], "ascending")],
+        )
+        self.add_operator("order", operator=order_by_node)
+        self.link_operators(show_node, "order")
+
     def _naive_select_planner(self, ast, statistics):
         """
         The naive planner only works on single tables and always puts operations in

opteryx/managers/query/planner/temporal.py

@@ -51,6 +51,7 @@
     r"FULL\sOUTER\sJOIN",
     r"JOIN",
     r"WITH",
+    r"SHOW",
 ]
 
 COMBINE_WHITESPACE_REGEX = re.compile(r"\s+")

opteryx/operators/__init__.py

@@ -27,7 +27,8 @@
 from .outer_join_node import OuterJoinNode  # LEFT/RIGHT/FULL OUTER JOIN
 from .projection_node import ProjectionNode  # remove unwanted columns including renames
 from .selection_node import SelectionNode  # filter unwanted rows
-from .show_columns import ShowColumnsNode  # column details
+from .show_columns_node import ShowColumnsNode  # column details
+from .show_functions_node import ShowFunctionsNode  # supported functions
 from .sort_node import SortNode  # order by selected columns
 
 

opteryx/operators/show_functions_node.py

@@ -0,0 +1,60 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Show Functions Node
+
+This is a SQL Query Execution Plan Node.
+"""
+from typing import Iterable
+import pyarrow
+
+from opteryx import operators, functions
+from opteryx.models import Columns, QueryDirectives, QueryStatistics
+from opteryx.operators import BasePlanNode
+
+
+class ShowFunctionsNode(BasePlanNode):
+    def __init__(
+        self, directives: QueryDirectives, statistics: QueryStatistics, **config
+    ):
+        super().__init__(directives=directives, statistics=statistics)
+        self._full = config.get("full")
+        self._extended = config.get("extended")
+
+    @property
+    def name(self):  # pragma: no cover
+        return "Show Functions"
+
+    @property
+    def config(self):  # pragma: no cover
+        return ""
+
+    def execute(self) -> Iterable:
+
+        buffer = []
+
+        for function in functions.functions():
+            buffer.append({"name": function, "type": "function"})
+        for aggregate in operators.aggregators():
+            buffer.append({"name": aggregate, "type": "aggregator"})
+
+        table = pyarrow.Table.from_pylist(buffer)
+        table = Columns.create_table_metadata(
+            table=table,
+            expected_rows=len(buffer),
+            name="show_columns",
+            table_aliases=[],
+        )
+
+        yield table
+        return

tests/query_execution/test_show_functions.py

@@ -0,0 +1,30 @@
+"""
+Test show functions works; the number of functions is constantly changing so test it's
+more than it was when we last reviewed this test.
+"""
+import os
+import sys
+
+sys.path.insert(1, os.path.join(sys.path[0], "../.."))
+
+
+def test_documentation_connect_example():
+
+    import opteryx
+
+    conn = opteryx.connect()
+    cur = conn.cursor()
+    cur.execute("SHOW FUNCTIONS")
+    rows = cur.fetchall()
+
+    # below here is not in the documentation
+    rows = list(rows)
+    assert len(rows) > 85, len(rows)
+    conn.close()
+
+
+if __name__ == "__main__":  # pragma: no cover
+
+    test_documentation_connect_example()
+
+    print("✅ okay")