[sql lab] reduce the number of metadata calls when loading a table (#4593)

superset/db_engine_specs.py

@@ -29,6 +29,7 @@ import boto3
 from flask import g
 from flask_babel import lazy_gettext as _
 import pandas
+import sqlalchemy as sqla
 from sqlalchemy import select
 from sqlalchemy.engine import create_engine
 from sqlalchemy.engine.url import make_url
@@ -231,14 +232,15 @@ class BaseEngineSpec(object):
 
     @classmethod
     def select_star(cls, my_db, table_name, schema=None, limit=100,
-                    show_cols=False, indent=True, latest_partition=True):
+                    show_cols=False, indent=True, latest_partition=True,
+                    cols=None):
         fields = '*'
-        cols = []
-        if show_cols or latest_partition:
-            cols = my_db.get_table(table_name, schema=schema).columns
+        cols = cols or []
+        if (show_cols or latest_partition) and not cols:
+            cols = my_db.get_columns(table_name, schema)
 
         if show_cols:
-            fields = [my_db.get_quoter()(c.name) for c in cols]
+            fields = [sqla.column(c.get('name')) for c in cols]
         full_table_name = table_name
         if schema:
             full_table_name = schema + '.' + table_name

superset/models/core.py

@@ -680,7 +680,8 @@ class Database(Model, AuditMixinNullable, ImportMixin):
 
         DB_CONNECTION_MUTATOR = config.get('DB_CONNECTION_MUTATOR')
         if DB_CONNECTION_MUTATOR:
-            url, params = DB_CONNECTION_MUTATOR(url, params, user_name, sm)
+            url, params = DB_CONNECTION_MUTATOR(
+                url, params, effective_username, sm)
         return create_engine(url, **params)
 
     def get_reserved_words(self):
@@ -713,11 +714,11 @@ class Database(Model, AuditMixinNullable, ImportMixin):
 
     def select_star(
             self, table_name, schema=None, limit=100, show_cols=False,
-            indent=True, latest_partition=True):
+            indent=True, latest_partition=True, cols=None):
         """Generates a ``select *`` statement in the proper dialect"""
         return self.db_engine_spec.select_star(
             self, table_name, schema=schema, limit=limit, show_cols=show_cols,
-            indent=indent, latest_partition=latest_partition)
+            indent=indent, latest_partition=latest_partition, cols=cols)
 
     def wrap_sql_limit(self, sql, limit=1000):
         qry = (

superset/views/core.py

@@ -2212,11 +2212,12 @@ class Superset(BaseSupersetView):
     def table(self, database_id, table_name, schema):
         schema = utils.js_string_to_python(schema)
         mydb = db.session.query(models.Database).filter_by(id=database_id).one()
-        cols = []
+        payload_columns = []
         indexes = []
-        t = mydb.get_columns(table_name, schema)
+        primary_key = []
+        foreign_keys = []
         try:
-            t = mydb.get_columns(table_name, schema)
+            columns = mydb.get_columns(table_name, schema)
             indexes = mydb.get_indexes(table_name, schema)
             primary_key = mydb.get_pk_constraint(table_name, schema)
             foreign_keys = mydb.get_foreign_keys(table_name, schema)
@@ -2235,13 +2236,13 @@ class Superset(BaseSupersetView):
             idx['type'] = 'index'
         keys += indexes
 
-        for col in t:
+        for col in columns:
             dtype = ''
             try:
                 dtype = '{}'.format(col['type'])
             except Exception:
                 pass
-            cols.append({
+            payload_columns.append({
                 'name': col['name'],
                 'type': dtype.split('(')[0] if '(' in dtype else dtype,
                 'longType': dtype,
@@ -2252,9 +2253,10 @@ class Superset(BaseSupersetView):
             })
         tbl = {
             'name': table_name,
-            'columns': cols,
+            'columns': payload_columns,
             'selectStar': mydb.select_star(
-                table_name, schema=schema, show_cols=True, indent=True),
+                table_name, schema=schema, show_cols=True, indent=True,
+                cols=columns, latest_partition=False),
             'primaryKey': primary_key,
             'foreignKeys': foreign_keys,
             'indexes': keys,

tests/model_tests.py

@@ -4,14 +4,16 @@ from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
 
-import unittest
+import textwrap
 
 from sqlalchemy.engine.url import make_url
+from tests.base_tests import SupersetTestCase
 
+from superset import db
 from superset.models.core import Database
 
 
-class DatabaseModelTestCase(unittest.TestCase):
+class DatabaseModelTestCase(SupersetTestCase):
 
     def test_database_schema_presto(self):
         sqlalchemy_uri = 'presto://presto.airbnb.io:8080/hive/default'
@@ -73,3 +75,25 @@ class DatabaseModelTestCase(unittest.TestCase):
         model.impersonate_user = False
         user_name = make_url(model.get_sqla_engine(user_name=example_user).url).username
         self.assertNotEquals(example_user, user_name)
+
+    def test_select_star(self):
+        main_db = self.get_main_database(db.session)
+        table_name = 'bart_lines'
+        sql = main_db.select_star(
+            table_name, show_cols=False, latest_partition=False)
+        expected = textwrap.dedent("""\
+        SELECT *
+        FROM {table_name}
+        LIMIT 100""".format(**locals()))
+        assert sql.startswith(expected)
+
+        sql = main_db.select_star(
+            table_name, show_cols=True, latest_partition=False)
+        expected = textwrap.dedent("""\
+        SELECT color,
+               name,
+               path_json,
+               polyline
+        FROM bart_lines
+        LIMIT 100""".format(**locals()))
+        assert sql.startswith(expected)