feat: describe view information_schema.*

tekumara · Aug 9, 2024 · facc390 · facc390
1 parent b874fc1
commit facc390
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Showing 4 changed files with 58 additions and 5 deletions.
diff --git a/fakesnow/fakes.py b/fakesnow/fakes.py
@@ -114,7 +114,6 @@ def describe(self, command: str, *args: Any, **kwargs: Any) -> list[ResultMetada
     def description(self) -> list[ResultMetadata]:
         # use a separate cursor to avoid consuming the result set on this cursor
         with self._conn.cursor() as cur:
-            # self._duck_conn.execute(sql, params)
             expression = sqlglot.parse_one(f"DESCRIBE {self._last_sql}", read="duckdb")
             cur._execute(expression, self._last_params)  # noqa: SLF001
             meta = FakeSnowflakeCursor._describe_as_result_metadata(cur.fetchall())

diff --git a/fakesnow/info_schema.py b/fakesnow/info_schema.py
@@ -78,6 +78,7 @@
 """
 )
 
+
 # replicates https://docs.snowflake.com/sql-reference/info-schema/databases
 SQL_CREATE_INFORMATION_SCHEMA_DATABASES_VIEW = Template(
     """

diff --git a/fakesnow/transforms.py b/fakesnow/transforms.py
@@ -170,6 +170,25 @@ def create_database(expression: exp.Expression, db_path: Path | None = None) ->
 """
 )
 
+SQL_DESCRIBE_INFO_SCHEMA = Template(
+    """
+SELECT
+    column_name AS "name",
+    column_type as "type",
+    'COLUMN' AS "kind",
+    CASE WHEN "null" = 'YES' THEN 'Y' ELSE 'N' END AS "null?",
+    NULL::VARCHAR AS "default",
+    'N' AS "primary key",
+    'N' AS "unique key",
+    NULL::VARCHAR AS "check",
+    NULL::VARCHAR AS "expression",
+    NULL::VARCHAR AS "comment",
+    NULL::VARCHAR AS "policy name",
+    NULL::JSON AS "privacy domain",
+FROM (DESCRIBE information_schema.${view})
+"""
+)
+
 
 def describe_table(
     expression: exp.Expression, current_database: str | None = None, current_schema: str | None = None
@@ -191,7 +210,7 @@ def describe_table(
 
         if schema and schema.upper() == "INFORMATION_SCHEMA":
             # information schema views don't exist in _fs_columns_snowflake
-            return expression
+            return sqlglot.parse_one(SQL_DESCRIBE_INFO_SCHEMA.substitute(view=table.name), read="duckdb")
 
         return sqlglot.parse_one(
             SQL_DESCRIBE_TABLE.substitute(catalog=catalog, schema=schema, table=table.name),

diff --git a/tests/test_info_schema.py b/tests/test_info_schema.py
@@ -38,11 +38,45 @@ def test_info_schema_columns_describe(cur: snowflake.connector.cursor.SnowflakeC
 
     assert cur.description == expected_metadata
 
+
+def test_describe_view_columns(dcur: snowflake.connector.cursor.DictCursor):
+    cols = [
+        "name",
+        "type",
+        "kind",
+        "null?",
+        "default",
+        "primary key",
+        "unique key",
+        "check",
+        "expression",
+        "comment",
+        "policy name",
+        "privacy domain",
+    ]
+    dcur.execute("describe view information_schema.columns")
+    result: list[dict] = dcur.fetchall()  # type: ignore
+    assert list(result[0].keys()) == cols
+    names = [r["name"] for r in result]
     # should contain snowflake-specific columns (from _FS_COLUMNS_SNOWFLAKE)
-    cur.execute("describe view information_schema.columns")
-    result = cur.fetchall()
-    names = [name for (name, *_) in result]
     assert "comment" in names
+    # fmt: off
+    assert dcur.description[:-1] == [
+        ResultMetadata(name='name', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='type', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='kind', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='null?', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='default', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='primary key', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='unique key', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='check', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='expression', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='comment', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        ResultMetadata(name='policy name', type_code=2, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True),
+        # TODO: ignore the following, see https://github.com/tekumara/fakesnow/issues/26
+        # ResultMetadata(name='privacy domain', type_code=9, display_size=None, internal_size=16777216, precision=None, scale=None, is_nullable=True)
+    ]
+    # fmt: on
 
 
 def test_info_schema_columns_numeric(cur: snowflake.connector.cursor.SnowflakeCursor):