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11
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aaronmk
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# Database access
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import random
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import re
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import sys
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300
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aaronmk
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import exc
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131
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aaronmk
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import util
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11
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aaronmk
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832
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aaronmk
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##### Exceptions
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135
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aaronmk
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def get_cur_query(cur):
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if hasattr(cur, 'query'): return cur.query
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elif hasattr(cur, '_last_executed'): return cur._last_executed
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else: return None
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14
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aaronmk
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300
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aaronmk
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def _add_cursor_info(e, cur): exc.add_msg(e, 'query: '+get_cur_query(cur))
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135
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aaronmk
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300
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class DbException(exc.ExceptionWithCause):
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14
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def __init__(self, msg, cause=None, cur=None):
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300
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exc.ExceptionWithCause.__init__(self, msg, cause)
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14
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if cur != None: _add_cursor_info(self, cur)
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360
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class NameException(DbException): pass
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468
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class ExceptionWithColumns(DbException):
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def __init__(self, cols, cause=None):
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DbException.__init__(self, 'columns: ' + ', '.join(cols), cause)
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self.cols = cols
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11
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aaronmk
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468
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aaronmk
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class DuplicateKeyException(ExceptionWithColumns): pass
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13
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468
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class NullValueException(ExceptionWithColumns): pass
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13
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89
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class EmptyRowException(DbException): pass
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832
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aaronmk
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##### Input validation
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11
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aaronmk
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def check_name(name):
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if re.search(r'\W', name) != None: raise NameException('Name "'+name
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+'" may contain only alphanumeric characters and _')
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643
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aaronmk
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def esc_name(db, name):
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module = util.root_module(db)
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645
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aaronmk
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if module == 'psycopg2': return name
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# Don't enclose in quotes because this disables case-insensitivity
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643
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aaronmk
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elif module == 'MySQLdb': quote = '`'
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645
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aaronmk
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else: raise NotImplementedError("Can't escape name for "+module+' database')
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643
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aaronmk
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return quote + name.replace(quote, '') + quote
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832
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aaronmk
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##### Querying
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830
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def run_raw_query(db, query, params=None):
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cur = db.cursor()
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try: cur.execute(query, params)
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46
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aaronmk
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except Exception, e:
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_add_cursor_info(e, cur)
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raise
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return cur
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832
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aaronmk
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##### Recoverable querying
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15
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aaronmk
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11
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aaronmk
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def with_savepoint(db, func):
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savepoint = 'savepoint_'+str(random.randint(0, sys.maxint)) # must be unique
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830
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aaronmk
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run_raw_query(db, 'SAVEPOINT '+savepoint)
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11
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try: return_val = func()
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except:
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830
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run_raw_query(db, 'ROLLBACK TO SAVEPOINT '+savepoint)
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11
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raise
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else:
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830
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aaronmk
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run_raw_query(db, 'RELEASE SAVEPOINT '+savepoint)
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11
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return return_val
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830
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aaronmk
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def run_query(db, query, params=None, recover=None):
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if recover == None: recover = False
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def run(): return run_raw_query(db, query, params)
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if recover: return with_savepoint(db, run)
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else: return run()
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832
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aaronmk
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##### Result retrieval
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def col(cur, idx): return cur.description[idx][0]
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def rows(cur): return iter(lambda: cur.fetchone(), None)
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def row(cur): return rows(cur).next()
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def value(cur): return row(cur)[0]
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def values(cur): return iter(lambda: value(cur), None)
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def value_or_none(cur):
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try: return value(cur)
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except StopIteration: return None
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##### Basic queries
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830
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aaronmk
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def select(db, table, fields, conds, limit=None, recover=None):
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135
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aaronmk
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assert limit == None or type(limit) == int
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15
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check_name(table)
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map(check_name, fields)
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map(check_name, conds.keys())
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11
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aaronmk
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def cond(entry):
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13
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aaronmk
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col, value = entry
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644
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aaronmk
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cond_ = esc_name(db, col)+' '
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11
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aaronmk
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if value == None: cond_ += 'IS'
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else: cond_ += '='
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cond_ += ' %s'
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return cond_
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644
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aaronmk
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query = ('SELECT ' + ', '.join([esc_name(db, field) for field in fields])
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+ ' FROM '+esc_name(db, table))
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89
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aaronmk
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if conds != {}:
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query += ' WHERE '+' AND '.join(map(cond, conds.iteritems()))
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92
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aaronmk
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if limit != None: query += ' LIMIT '+str(limit)
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830
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aaronmk
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return run_query(db, query, conds.values(), recover)
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11
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aaronmk
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830
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aaronmk
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def insert(db, table, row, recover=None):
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11
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aaronmk
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check_name(table)
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13
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aaronmk
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cols = row.keys()
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15
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aaronmk
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map(check_name, cols)
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89
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aaronmk
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query = 'INSERT INTO '+table
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if row != {}: query += ' ('+', '.join(cols)+') VALUES ('\
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+', '.join(['%s']*len(cols))+')'
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else: query += ' DEFAULT VALUES'
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830
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aaronmk
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return run_query(db, query, row.values(), recover)
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11
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aaronmk
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135
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aaronmk
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def last_insert_id(db):
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module = util.root_module(db)
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if module == 'psycopg2': return value(run_query(db, 'SELECT lastval()'))
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elif module == 'MySQLdb': return db.insert_id()
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else: return None
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13
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aaronmk
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832
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aaronmk
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def truncate(db, table):
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check_name(table)
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return run_query(db, 'TRUNCATE '+table+' CASCADE')
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##### Database structure queries
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def pkey(db, cache, table, recover=None):
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'''Assumed to be first column in table'''
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check_name(table)
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if table not in cache:
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cache[table] = col(run_query(db, 'SELECT * FROM '+table+' LIMIT 0',
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834
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aaronmk
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recover=recover), 0)
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832
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aaronmk
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return cache[table]
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464
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aaronmk
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def constraint_cols(db, table, constraint):
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check_name(table)
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check_name(constraint)
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module = util.root_module(db)
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if module == 'psycopg2':
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return list(values(run_query(db, '''\
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SELECT attname
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FROM pg_constraint
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JOIN pg_class ON pg_class.oid = conrelid
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JOIN pg_attribute ON attrelid = conrelid AND attnum = ANY (conkey)
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WHERE
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relname = %(table)s
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AND conname = %(constraint)s
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ORDER BY attnum
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''',
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{'table': table, 'constraint': constraint})))
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else: raise NotImplementedError("Can't list constraint columns for "+module+
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' database')
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832
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aaronmk
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def tables(db):
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module = util.root_module(db)
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if module == 'psycopg2':
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return values(run_query(db, "SELECT tablename from pg_tables "
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"WHERE schemaname = 'public' ORDER BY tablename"))
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elif module == 'MySQLdb': return values(run_query(db, 'SHOW TABLES'))
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else: raise NotImplementedError("Can't list tables for "+module+' database')
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830
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aaronmk
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833
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aaronmk
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##### Database management
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def empty_db(db):
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for table in tables(db): truncate(db, table)
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832
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aaronmk
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##### Heuristic queries
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14
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aaronmk
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def try_insert(db, table, row):
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830
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aaronmk
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'''Recovers from errors'''
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try: return insert(db, table, row, recover=True)
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46
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aaronmk
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except Exception, e:
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msg = str(e)
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465
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aaronmk
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match = re.search(r'duplicate key value violates unique constraint '
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r'"(([^\W_]+)_[^"]+)"', msg)
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if match:
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constraint, table = match.groups()
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try: cols = constraint_cols(db, table, constraint)
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except NotImplementedError: raise e
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851
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aaronmk
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else: raise DuplicateKeyException(cols, e)
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13
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aaronmk
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match = re.search(r'null value in column "(\w+)" violates not-null '
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'constraint', msg)
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470
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aaronmk
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if match: raise NullValueException([match.group(1)], e)
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13
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aaronmk
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raise # no specific exception raised
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11
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aaronmk
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471
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aaronmk
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def put(db, table, row, pkey, row_ct_ref=None):
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830
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aaronmk
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'''Recovers from errors'''
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471
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aaronmk
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try:
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row_ct = try_insert(db, table, row).rowcount
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if row_ct_ref != None and row_ct >= 0: row_ct_ref[0] += row_ct
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return last_insert_id(db)
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except DuplicateKeyException, e:
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830
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aaronmk
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return value(select(db, table, [pkey], util.dict_subset(row, e.cols),
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recover=True))
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471
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aaronmk
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473
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aaronmk
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def get(db, table, row, pkey, row_ct_ref=None, create=False):
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830
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aaronmk
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'''Recovers from errors'''
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try: return value(select(db, table, [pkey], row, 1, recover=True))
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14
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aaronmk
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except StopIteration:
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40
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aaronmk
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if not create: raise
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| 214 |
471
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aaronmk
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return put(db, table, row, pkey, row_ct_ref) # insert new row
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| 215 |
131
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aaronmk
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832
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aaronmk
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##### Database connections
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131
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aaronmk
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db_engines = {
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'MySQL': ('MySQLdb', {'password': 'passwd', 'database': 'db'}),
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'PostgreSQL': ('psycopg2', {}),
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}
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360
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aaronmk
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DatabaseErrors_set = set([DbException])
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DatabaseErrors = tuple(DatabaseErrors_set)
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| 225 |
342
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aaronmk
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def _add_module(module):
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DatabaseErrors_set.add(module.DatabaseError)
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global DatabaseErrors
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DatabaseErrors = tuple(DatabaseErrors_set)
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646
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aaronmk
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def connect(db_config, serializable=True):
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131
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aaronmk
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db_config = db_config.copy() # don't modify input!
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| 233 |
342
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aaronmk
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module_name, mappings = db_engines[db_config.pop('engine')]
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module = __import__(module_name)
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_add_module(module)
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330
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aaronmk
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for orig, new in mappings.iteritems():
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try: util.rename_key(db_config, orig, new)
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except KeyError: pass
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| 239 |
646
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aaronmk
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db = module.connect(**db_config)
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if serializable:
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| 241 |
830
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aaronmk
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run_raw_query(db, 'SET TRANSACTION ISOLATION LEVEL SERIALIZABLE')
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| 242 |
646
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aaronmk
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return db
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def db_config_str(db_config):
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return db_config['engine']+' database '+db_config['database']
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