Improve examples & related tests (#7773)

* [WiP] improve load_examples

related to #7472, longer term we will generate the examples by exporting
them into tarball as in #7472. In the meantime, we need this subset of
the features:

* allowing specifying an alternate database connection for examples
* allowing a --only-metadata flag to `load_examples` to load only
  dashboard and chart definitions, no actual data is loaded

* Improve logging

* Rename data->examples

* Load only if not exist

* By default do not load, add a force flag

* fix build

* set published to true

superset/examples/unicode_test_data.py

@@ -0,0 +1,163 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+import datetime
+import json
+import random
+
+import pandas as pd
+from sqlalchemy import Date, Float, String
+
+from superset import db
+from superset.utils import core as utils
+from .helpers import (
+    config,
+    Dash,
+    get_example_data,
+    get_slice_json,
+    merge_slice,
+    Slice,
+    TBL,
+    update_slice_ids,
+)
+
+
+def load_unicode_test_data(only_metadata=False, force=False):
+    """Loading unicode test dataset from a csv file in the repo"""
+    tbl_name = "unicode_test"
+    database = utils.get_example_database()
+    table_exists = database.has_table_by_name(tbl_name)
+
+    if not only_metadata and (not table_exists or force):
+        data = get_example_data(
+            "unicode_utf8_unixnl_test.csv", is_gzip=False, make_bytes=True
+        )
+        df = pd.read_csv(data, encoding="utf-8")
+        # generate date/numeric data
+        df["dttm"] = datetime.datetime.now().date()
+        df["value"] = [random.randint(1, 100) for _ in range(len(df))]
+        df.to_sql(  # pylint: disable=no-member
+            tbl_name,
+            database.get_sqla_engine(),
+            if_exists="replace",
+            chunksize=500,
+            dtype={
+                "phrase": String(500),
+                "short_phrase": String(10),
+                "with_missing": String(100),
+                "dttm": Date(),
+                "value": Float(),
+            },
+            index=False,
+        )
+        print("Done loading table!")
+        print("-" * 80)
+
+    print("Creating table [unicode_test] reference")
+    obj = db.session.query(TBL).filter_by(table_name=tbl_name).first()
+    if not obj:
+        obj = TBL(table_name=tbl_name)
+    obj.main_dttm_col = "dttm"
+    obj.database = database
+    db.session.merge(obj)
+    db.session.commit()
+    obj.fetch_metadata()
+    tbl = obj
+
+    slice_data = {
+        "granularity_sqla": "dttm",
+        "groupby": [],
+        "metric": {
+            "aggregate": "SUM",
+            "column": {"column_name": "value"},
+            "expressionType": "SIMPLE",
+            "label": "Value",
+        },
+        "row_limit": config.get("ROW_LIMIT"),
+        "since": "100 years ago",
+        "until": "now",
+        "where": "",
+        "viz_type": "word_cloud",
+        "size_from": "10",
+        "series": "short_phrase",
+        "size_to": "70",
+        "rotation": "square",
+        "limit": "100",
+    }
+
+    print("Creating a slice")
+    slc = Slice(
+        slice_name="Unicode Cloud",
+        viz_type="word_cloud",
+        datasource_type="table",
+        datasource_id=tbl.id,
+        params=get_slice_json(slice_data),
+    )
+    merge_slice(slc)
+
+    print("Creating a dashboard")
+    dash = db.session.query(Dash).filter_by(slug="unicode-test").first()
+
+    if not dash:
+        dash = Dash()
+    js = """\
+{
+    "CHART-Hkx6154FEm": {
+        "children": [],
+        "id": "CHART-Hkx6154FEm",
+        "meta": {
+            "chartId": 2225,
+            "height": 30,
+            "sliceName": "slice 1",
+            "width": 4
+        },
+        "type": "CHART"
+    },
+    "GRID_ID": {
+        "children": [
+            "ROW-SyT19EFEQ"
+        ],
+        "id": "GRID_ID",
+        "type": "GRID"
+    },
+    "ROOT_ID": {
+        "children": [
+            "GRID_ID"
+        ],
+        "id": "ROOT_ID",
+        "type": "ROOT"
+    },
+    "ROW-SyT19EFEQ": {
+        "children": [
+            "CHART-Hkx6154FEm"
+        ],
+        "id": "ROW-SyT19EFEQ",
+        "meta": {
+            "background": "BACKGROUND_TRANSPARENT"
+        },
+        "type": "ROW"
+    },
+    "DASHBOARD_VERSION_KEY": "v2"
+}
+    """
+    dash.dashboard_title = "Unicode Test"
+    pos = json.loads(js)
+    update_slice_ids(pos, [slc])
+    dash.position_json = json.dumps(pos, indent=4)
+    dash.slug = "unicode-test"
+    dash.slices = [slc]
+    db.session.merge(dash)
+    db.session.commit()