Pandas import update (#176)

* Pandas import update\nNulls on nullable columns is OK

* fix show tables difference

doltpy/cli/write.py

@@ -43,8 +43,10 @@ def write_pandas(
     """
 
     def writer(filepath: str):
-        clean = df.dropna(subset=primary_key)
-        clean.to_csv(filepath, index=False)
+        filtered = df
+        if import_mode != "update":
+            filtered = df.dropna(subset=primary_key)
+        filtered.to_csv(filepath, index=False)
         return filepath
 
     _import_helper(

doltpy/sql/sql.py

@@ -350,8 +350,8 @@ def get_query(table: str) -> str:
 
     def tables(self) -> List[str]:
         with self.engine.connect() as conn:
-            result = conn.execute("SHOW TABLES")
-            return [row["Table"] for row in result]
+            result = conn.execute("select table_name from information_schema.tables where table_schema = DATABASE();")
+            return [row["table_name"] for row in result]
 
 
 class DoltSQLEngineContext(DoltSQLContext):

tests/cli/test_write.py

@@ -1,6 +1,7 @@
-from doltpy.cli.write import write_pandas, CREATE
+from doltpy.cli.write import write_pandas, CREATE, UPDATE
 from doltpy.cli.read import read_rows
 from .helpers import compare_rows
+import numpy as np
 import pandas as pd
 
 
@@ -19,4 +20,16 @@ def test_write_pandas(init_empty_test_repo):
     compare_rows(expected, actual, "id")
 
 
+def test_write_pandas_accept_nulls_on_update(init_empty_test_repo):
+    NULL_ROWS = [
+        {"name": "Anna", "adjective": "tragic", "id": "1", "date_of_death": "1877-01-01"},
+        {"name": "Vronksy", "adjective": "honorable", "id": "2", "date_of_death": ""},
+        {"name": "Oblonsky", "adjective": "buffoon", "id": "3", "date_of_death": np.NaN},
+    ]
+    dolt = init_empty_test_repo
+    write_pandas(dolt, "characters", pd.DataFrame(NULL_ROWS[:2]), CREATE, ["id"])
+    write_pandas(dolt, "characters", pd.DataFrame(NULL_ROWS[2:]), UPDATE)
+    actual = read_rows(dolt, "characters")
+    expected = pd.DataFrame(NULL_ROWS).to_dict("records")
+    compare_rows(expected, actual, "id")