datasette_pytables/__init__.py

   1 from moz_sql_parser import parse
   2 import re
   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 = ['value']
  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, params):
  33     # Table name
  34     sql = re.sub('(?i)from \[(.*)]', 'from "\g<1>"', sql)
  35     # Params
  36     for param in params:
  37         sql = sql.replace(":" + param, param)
  38
  39     try:
  40         parsed = parse(sql)
  41     except:
  42         # Propably it's a PyTables expression
  43         for token in ['group by', 'order by', 'limit', '']:
  44             res = re.search('(?i)where (.*)' + token, sql)
  45             if res:
  46                 modified_sql = re.sub('(?i)where (.*)(' + token + ')', '\g<2>', sql)
  47                 parsed = parse(modified_sql)
  48                 parsed['where'] = res.group(1).strip()
  49                 break
  50
  51     # Always a list of fields
  52     if type(parsed['select']) is not list:
  53         parsed['select'] = [parsed['select']]
  54
  55     return parsed
  56
  57 _operators = {
  58     'eq': '==',
  59     'neq': '!=',
  60     'gt': '>',
  61     'gte': '>=',
  62     'lt': '<',
  63     'lte': '<=',
  64     'and': '&',
  65     'or': '|',
  66 }
  67
  68 class Connection:
  69     def __init__(self, path):
  70         self.path = path
  71         self.h5file = tables.open_file(path)
  72
  73     def execute(self, sql, params=None, truncate=False, page_size=None, max_returned_rows=None):
  74         if params is None:
  75             params = {}
  76         rows = []
  77         truncated = False
  78         description = []
  79
  80         parsed_sql = _parse_sql(sql, params)
  81
  82         if parsed_sql['from'] == 'sqlite_master':
  83             rows = self._execute_datasette_query(sql, params)
  84             description = (('value',))
  85             return rows, truncated, description
  86
  87         table = self.h5file.get_node(parsed_sql['from'])
  88         table_rows = []
  89         fields = parsed_sql['select']
  90         colnames = ['value']
  91         if type(table) is tables.table.Table:
  92             colnames = table.colnames
  93
  94         query = ''
  95         start = 0
  96         end = table.nrows
  97
  98         # Use 'where' statement or get all the rows
  99         def _cast_param(field, pname):
 100             # Cast value to the column type
 101             coltype = table.dtype.name
 102             if type(table) is tables.table.Table:
 103                 coltype = table.coltypes[field]
 104             fcast = None
 105             if coltype == 'string':
 106                 fcast = str
 107             elif coltype.startswith('int'):
 108                 fcast = int
 109             elif coltype.startswith('float'):
 110                 fcast = float
 111             if fcast:
 112                 params[pname] = fcast(params[pname])
 113
 114         def _translate_where(where):
 115             # Translate SQL to PyTables expression
 116             nonlocal start, end
 117             expr = ''
 118             operator = list(where)[0]
 119
 120             if operator in ['and', 'or']:
 121                 subexpr = [_translate_where(e) for e in where[operator]]
 122                 subexpr = filter(lambda e: e, subexpr)
 123                 subexpr = ["({})".format(e) for e in subexpr]
 124                 expr = " {} ".format(_operators[operator]).join(subexpr)
 125             elif operator == 'exists':
 126                 pass
 127             elif where == {'eq': ['rowid', 'p0']}:
 128                 start = int(params['p0'])
 129                 end = start + 1
 130             elif where == {'gt': ['rowid', 'p0']}:
 131                 start = int(params['p0']) + 1
 132             else:
 133                 left, right = where[operator]
 134                 if left in params:
 135                     _cast_param(right, left)
 136                 elif right in params:
 137                     _cast_param(left, right)
 138
 139                 expr = "{left} {operator} {right}".format(left=left, operator=_operators.get(operator, operator), right=right)
 140
 141             return expr
 142
 143         if 'where' in parsed_sql:
 144             if type(parsed_sql['where']) is dict:
 145                 query = _translate_where(parsed_sql['where'])
 146             else:
 147                 query = parsed_sql['where']
 148
 149         # Limit number of rows
 150         limit = None
 151         if 'limit' in parsed_sql:
 152             limit = int(parsed_sql['limit'])
 153
 154         # Truncate if needed
 155         if page_size and max_returned_rows and truncate:
 156             if max_returned_rows == page_size:
 157                 max_returned_rows += 1
 158
 159         # Execute query
 160         if query:
 161             table_rows = table.where(query, params, start, end)
 162         else:
 163             table_rows = table.iterrows(start, end)
 164
 165         # Prepare rows
 166         def normalize_field_value(value):
 167             if type(value) is bytes:
 168                 return value.decode('utf-8')
 169             elif not type(value) in (int, float, complex):
 170                 return str(value)
 171             else:
 172                 return value
 173
 174         def make_get_rowid():
 175             if type(table) is tables.table.Table:
 176                 def get_rowid(row):
 177                     return int(row.nrow)
 178             else:
 179                 rowid = start - 1
 180                 def get_rowid(row):
 181                     nonlocal rowid
 182                     rowid += 1
 183                     return rowid
 184             return get_rowid
 185
 186         def make_get_row_value():
 187             if type(table) is tables.table.Table:
 188                 def get_row_value(row, field):
 189                     return row[field]
 190             else:
 191                 def get_row_value(row, field):
 192                     return row
 193             return get_row_value
 194
 195         if len(fields) == 1 and type(fields[0]['value']) is dict and \
 196            fields[0]['value'].get('count') == '*':
 197             rows.append(Row({'count(*)': int(table.nrows)}))
 198         else:
 199             get_rowid = make_get_rowid()
 200             get_row_value = make_get_row_value()
 201             count = 0
 202             for table_row in table_rows:
 203                 count += 1
 204                 if limit and count > limit:
 205                     break
 206                 if truncate and max_returned_rows and count > max_returned_rows:
 207                     truncated = True
 208                     break
 209                 row = Row()
 210                 for field in fields:
 211                     field_name = field['value']
 212                     if type(field_name) is dict and 'distinct' in field_name:
 213                         field_name = field_name['distinct']
 214                     if field_name == 'rowid':
 215                         row['rowid'] = get_rowid(table_row)
 216                     elif field_name == '*':
 217                         for col in colnames:
 218                             row[col] = normalize_field_value(get_row_value(table_row, col))
 219                     else:
 220                         row[field_name] = normalize_field_value(get_row_value(table_row, field_name))
 221                 rows.append(row)
 222
 223         # Prepare query description
 224         for field in [f['value'] for f in fields]:
 225             if field == '*':
 226                 for col in colnames:
 227                     description.append((col,))
 228             else:
 229                 description.append((field,))
 230
 231         # Return the rows
 232         return rows, truncated, tuple(description)
 233
 234     def _execute_datasette_query(self, sql, params):
 235         "Datasette special queries for getting tables info"
 236         if sql == "SELECT count(*) from sqlite_master WHERE type = 'view' and name=:n":
 237             row = Row()
 238             row['count(*)'] = 0
 239             return [row]
 240         elif sql == 'select sql from sqlite_master where name = :n and type="table"':
 241             try:
 242                 table = self.h5file.get_node(params['n'])
 243                 colnames = ['value']
 244                 if type(table) is tables.table.Table:
 245                     colnames = table.colnames
 246                 row = Row()
 247                 row['sql'] = 'CREATE TABLE {} ({})'.format(params['n'], ", ".join(colnames))
 248                 return [row]
 249             except:
 250                 return []
 251         else:
 252             raise Exception("SQLite queries cannot be executed with this connector")
 253
 254 class Row(list):
 255     def __init__(self, values=None):
 256         self.labels = []
 257         self.values = []
 258         if values:
 259             for idx in values:
 260                 self.__setitem__(idx, values[idx])
 261
 262     def __setitem__(self, idx, value):
 263         if type(idx) is str:
 264             if idx in self.labels:
 265                 self.values[self.labels.index(idx)] = value
 266             else:
 267                 self.labels.append(idx)
 268                 self.values.append(value)
 269         else:
 270             self.values[idx] = value
 271
 272     def __getitem__(self, idx):
 273         if type(idx) is str:
 274             return self.values[self.labels.index(idx)]
 275         else:
 276             return self.values[idx]
 277
 278     def __iter__(self):
 279         return self.values.__iter__()