Support queries in PyTables style
[datasette-pytables.git] / datasette_pytables / __init__.py
1 from collections import OrderedDict
2 import sqlparse
3 import tables
4
5 _connector_type = 'pytables'
6
7 def inspect(path):
8     "Open file and return tables info"
9     h5tables = {}
10     views = []
11     h5file = tables.open_file(path)
12
13     for table in filter(lambda node: not(isinstance(node, tables.group.Group)), h5file):
14         colnames = []
15         if isinstance(table, tables.table.Table):
16             colnames = table.colnames
17
18         h5tables[table._v_pathname] = {
19             'name': table._v_pathname,
20             'columns': colnames,
21             'primary_keys': [],
22             'count': int(table.nrows),
23             'label_column': None,
24             'hidden': False,
25             'fts_table': None,
26             'foreign_keys': {'incoming': [], 'outgoing': []},
27         }
28
29     h5file.close()
30     return h5tables, views, _connector_type
31
32 def _parse_sql(sql):
33     parsed = sqlparse.parse(sql)
34     stmt = parsed[0]
35     parsed_sql = {}
36     current_keyword = ""
37     for token in stmt.tokens:
38         if token.is_keyword:
39             if current_keyword in parsed_sql and parsed_sql[current_keyword] == '':
40                 # Check composed keywords like 'order by'
41                 del parsed_sql[current_keyword]
42                 current_keyword += " " + str(token)
43             else:
44                 current_keyword = str(token)
45             parsed_sql[current_keyword] = ""
46         elif type(token) is sqlparse.sql.Where:
47             parsed_sql['where'] = token
48         else:
49             if not token.is_whitespace:
50                 parsed_sql[current_keyword] += str(token)
51     return parsed_sql
52
53 _operators = {
54     '=': '==',
55 }
56
57 def _translate_condition(table, condition, params):
58     field = condition.left.get_real_name()
59
60     operator = list(filter(lambda t: t.ttype == sqlparse.tokens.Comparison, condition.tokens))[0]
61     if operator.value in _operators:
62         operator = _operators[operator.value]
63     else:
64         operator = operator.value
65
66     value = condition.right.value
67     if value.startswith(':'):
68         # Value is a parameters
69         value = value[1:]
70         if value in params:
71             # Cast value to the column type
72             coltype = table.coltypes[field]
73             if coltype == 'string':
74                 params[value] = str(params[value])
75             elif coltype.startswith('int'):
76                 params[value] = int(params[value])
77             elif coltype.startswith('float'):
78                 params[value] = float(params[value])
79
80     translated = "{left} {operator} {right}".format(left=field, operator=operator, right=value)
81     return translated, params
82
83 class Connection:
84     def __init__(self, path):
85         self.path = path
86         self.h5file = tables.open_file(path)
87
88     def execute(self, sql, params=None, truncate=False):
89         if params is None:
90             params = {}
91         rows = []
92         truncated = False
93         description = []
94
95         parsed_sql = _parse_sql(sql)
96         table = self.h5file.get_node(parsed_sql['from'][1:-1])
97         table_rows = []
98         fields = parsed_sql['select'].split(',')
99
100         # Use 'where' statement or get all the rows
101         if 'where' in parsed_sql:
102             query = ''
103             start = 0
104             end = table.nrows
105             try:
106                 conditions = []
107                 for condition in parsed_sql['where'].get_sublists():
108                     if str(condition) == '"rowid"=:p0':
109                         start = int(params['p0'])
110                         end = start + 1
111                     else:
112                         translated, params = _translate_condition(table, condition, params)
113                         conditions.append(translated)
114                 if conditions:
115                     query = ') & ('.join(conditions)
116                     query = '(' + query + ')'
117             except:
118                 # Probably it's a PyTables query
119                 query = str(parsed_sql['where'])[6:]    # without where keyword
120
121             if query:
122                 table_rows = table.where(query, params, start, end)
123             else:
124                 table_rows = table.iterrows(start, end)
125         else:
126             table_rows = table.iterrows()
127
128         # Prepare rows
129         if len(fields) == 1 and fields[0] == 'count(*)':
130             rows.append(Row({fields[0]: int(table.nrows)}))
131         else:
132             for table_row in table_rows:
133                 row = Row()
134                 for field in fields:
135                     if field == 'rowid':
136                         row[field] = int(table_row.nrow)
137                     elif field == '*':
138                         for col in table.colnames:
139                             value = table_row[col]
140                             if type(value) is bytes:
141                                 value = value.decode('utf-8')
142                             row[col] = value
143                     else:
144                         row[field] = table_row[field]
145                 rows.append(row)
146
147         # Prepare query description
148         for field in fields:
149             if field == '*':
150                 for col in table.colnames:
151                     description.append((col,))
152             else:
153                 description.append((field,))
154
155         # Return the rows
156         if truncate:
157             return rows, truncated, tuple(description)
158         else:
159             return rows
160
161 class Row(OrderedDict):
162     def __getitem__(self, label):
163         if type(label) is int:
164             return super(OrderedDict, self).__getitem__(list(self.keys())[label])
165         else:
166             return super(OrderedDict, self).__getitem__(label)
167
168     def __iter__(self):
169         return self.values().__iter__()