1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
|
import re
import warnings
from contextlib import contextmanager
import pymssql # pylint: disable=import-error
from Orange.data import StringVariable, TimeVariable, ContinuousVariable, DiscreteVariable
from Orange.data.sql.backend import Backend
from Orange.data.sql.backend.base import ToSql, BackendError
def parse_ex(ex: Exception) -> str:
try:
return ex.args[0][1].decode().splitlines()[-1]
except: # pylint: disable=bare-except
return str(ex)
class PymssqlBackend(Backend):
display_name = "SQL Server"
def __init__(self, connection_params):
connection_params["server"] = connection_params.pop("host", None)
for key in list(connection_params):
if connection_params[key] is None:
del connection_params[key]
super().__init__(connection_params)
try:
self.connection = pymssql.connect(login_timeout=5, **connection_params)
except pymssql.Error as ex:
raise BackendError(parse_ex(ex)) from ex
except ValueError:
# ValueError is raised when 'server' contains "\\"
raise BackendError("Incorrect format of connection details")
def list_tables_query(self, schema=None):
return """
SELECT [TABLE_SCHEMA], [TABLE_NAME]
FROM information_schema.tables
WHERE TABLE_TYPE in ('VIEW' ,'BASE TABLE')
ORDER BY [TABLE_NAME]
"""
def n_tables_query(self, _=None) -> str:
return "SELECT COUNT(*) FROM information_schema.tables"
def quote_identifier(self, name):
return "[{}]".format(name)
def unquote_identifier(self, quoted_name):
return quoted_name[1:-1]
def create_sql_query(self, table_name, fields, filters=(),
group_by=None, order_by=None, offset=None, limit=None,
use_time_sample=None):
sql = ["SELECT"]
if limit and not offset:
sql.extend(["TOP", str(limit)])
sql.append(', '.join(fields))
sql.extend(["FROM", table_name])
if use_time_sample:
sql.append("TABLESAMPLE system_time(%i)" % use_time_sample)
if filters:
sql.extend(["WHERE", " AND ".join(filters)])
if group_by:
sql.extend(["GROUP BY", ", ".join(group_by)])
if offset and not order_by:
order_by = fields[0].split("AS")[1:]
if order_by:
sql.extend(["ORDER BY", ",".join(order_by)])
if offset:
sql.extend(["OFFSET", str(offset), "ROWS"])
if limit:
sql.extend(["FETCH FIRST", str(limit), "ROWS ONLY"])
return " ".join(sql)
@contextmanager
def execute_sql_query(self, query, params=()):
try:
with self.connection.cursor() as cur:
cur.execute(query, *params)
yield cur
except pymssql.Error as ex:
raise BackendError(parse_ex(ex)) from ex
def create_variable(self, field_name, field_metadata, type_hints, inspect_table=None):
if field_name in type_hints:
var = type_hints[field_name]
else:
var = self._guess_variable(field_name, field_metadata,
inspect_table)
field_name_q = self.quote_identifier(field_name)
if var.is_continuous:
if isinstance(var, TimeVariable):
var.to_sql = ToSql("DATEDIFF(s, '1970-01-01 00:00:00', {})".format(field_name_q))
else:
var.to_sql = ToSql(field_name_q)
else: # discrete or string
var.to_sql = ToSql(field_name_q)
return var
def _guess_variable(self, field_name, field_metadata, inspect_table):
# pylint: disable=import-error
from pymssql import STRING, NUMBER, DATETIME, DECIMAL
type_code, *_ = field_metadata
if type_code in (NUMBER, DECIMAL):
return ContinuousVariable(field_name)
if type_code == DATETIME:
tv = TimeVariable(field_name)
tv.have_date = True
tv.have_time = True
return tv
if type_code == STRING:
if inspect_table:
values = self.get_distinct_values(field_name, inspect_table)
if values:
return DiscreteVariable(field_name, values)
return StringVariable(field_name)
EST_ROWS_RE = re.compile(r'StatementEstRows="(\d+)"')
def count_approx(self, query):
with self.connection.cursor() as cur:
try:
cur.execute("SET SHOWPLAN_XML ON")
try:
cur.execute(query)
result = cur.fetchone()
match = self.EST_ROWS_RE.search(result[0])
if not match:
# Either StatementEstRows was not found or
# a float is received.
# If it is a float then it is most probable
# that the server's statistics are out of date
# and the result is false. In that case
# it is preferable to return None so
# an exact count be used.
return None
return int(match.group(1))
finally:
cur.execute("SET SHOWPLAN_XML OFF")
except pymssql.Error as ex:
if "SHOWPLAN permission denied" in str(ex):
warnings.warn("SHOWPLAN permission denied, count approximates will not be used")
return None
raise BackendError(parse_ex(ex)) from ex
def distinct_values_query(self, field_name: str, table_name: str) -> str:
field = self.quote_identifier(field_name)
return self.create_sql_query(
table_name,
[field],
# Cast - workaround for collations that are not case-sensitive and
# UTF characters sensitive
# DATALENGTH - workaround for string comparison that ignore trailing
# spaces, two strings that differ only in space in the end would
# group together if DATALENGTH wouldn't be used
group_by=[f"{field}, Cast({field} as binary), DATALENGTH({field})"],
order_by=[field],
limit=21,
)
|
