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         query = ''
 101         start = 0
 102         end = table.nrows
 103
 104         # Use 'where' statement or get all the rows
 105         if 'where' in parsed_sql:
 106             try:
 107                 conditions = []
 108                 for condition in parsed_sql['where'].get_sublists():
 109                     if str(condition) == '"rowid"=:p0':
 110                         start = int(params['p0'])
 111                         end = start + 1
 112                     else:
 113                         translated, params = _translate_condition(table, condition, params)
 114                         conditions.append(translated)
 115                 if conditions:
 116                     query = ') & ('.join(conditions)
 117                     query = '(' + query + ')'
 118             except:
 119                 # Probably it's a PyTables query
 120                 query = str(parsed_sql['where'])[6:]    # without where keyword
 121
 122         # Limit number of rows
 123         if 'limit' in parsed_sql:
 124             max_rows = int(parsed_sql['limit'])
 125             if end - start > max_rows:
 126                 end = start + max_rows
 127
 128         # Execute query
 129         if query:
 130             table_rows = table.where(query, params, start, end)
 131         else:
 132             table_rows = table.iterrows(start, end)
 133
 134         # Prepare rows
 135         if len(fields) == 1 and fields[0] == 'count(*)':
 136             rows.append(Row({fields[0]: int(table.nrows)}))
 137         else:
 138             for table_row in table_rows:
 139                 row = Row()
 140                 for field in fields:
 141                     if field == 'rowid':
 142                         row[field] = int(table_row.nrow)
 143                     elif field == '*':
 144                         for col in table.colnames:
 145                             value = table_row[col]
 146                             if type(value) is bytes:
 147                                 value = value.decode('utf-8')
 148                             row[col] = value
 149                     else:
 150                         row[field] = table_row[field]
 151                 rows.append(row)
 152
 153         # Prepare query description
 154         for field in fields:
 155             if field == '*':
 156                 for col in table.colnames:
 157                     description.append((col,))
 158             else:
 159                 description.append((field,))
 160
 161         # Return the rows
 162         if truncate:
 163             return rows, truncated, tuple(description)
 164         else:
 165             return rows
 166
 167 class Row(OrderedDict):
 168     def __getitem__(self, label):
 169         if type(label) is int:
 170             return super(OrderedDict, self).__getitem__(list(self.keys())[label])
 171         else:
 172             return super(OrderedDict, self).__getitem__(label)
 173
 174     def __iter__(self):
 175         return self.values().__iter__()