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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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aaronmk
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import ex
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aaronmk
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import util
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aaronmk
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aaronmk
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def _add_cursor_info(e, cur): ex.add_msg(e, 'query: '+cur.query)
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aaronmk
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class NameException(Exception): pass
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class DbException(ex.ExceptionWithCause):
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def __init__(self, msg, cause=None, cur=None):
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ex.ExceptionWithCause.__init__(self, msg, cause)
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if cur != None: _add_cursor_info(self, cur)
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class ExceptionWithColumn(DbException):
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def __init__(self, col, cause=None):
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DbException.__init__(self, 'column: '+col, cause)
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self.col = col
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class DuplicateKeyException(ExceptionWithColumn): pass
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class NullValueException(ExceptionWithColumn): pass
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class EmptyRowException(DbException): pass
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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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def run_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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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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def col(cur, idx): return cur.description[idx][0]
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def row(cur): return iter(lambda: cur.fetchone(), None).next()
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def value(cur): return row(cur)[0]
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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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run_query(db, 'SAVEPOINT '+savepoint)
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try: return_val = func()
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except:
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run_query(db, 'ROLLBACK TO SAVEPOINT '+savepoint)
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raise
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else:
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run_query(db, 'RELEASE SAVEPOINT '+savepoint)
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return return_val
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def select(db, table, fields, conds, limit=None):
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assert type(limit) == int
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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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def cond(entry):
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col, value = entry
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cond_ = col+' '
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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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query = 'SELECT '+', '.join(fields)+' FROM '+table
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if conds != {}:
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query += ' WHERE '+' AND '.join(map(cond, conds.iteritems()))
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if limit != None: query += ' LIMIT '+str(limit)
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return run_query(db, query, conds.values())
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def insert(db, table, row):
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check_name(table)
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cols = row.keys()
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map(check_name, cols)
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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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return run_query(db, query, row.values())
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def last_insert_id(db): return value(run_query(db, 'SELECT lastval()'))
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def try_insert(db, table, row):
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try: return with_savepoint(db, lambda: insert(db, table, row))
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except Exception, e:
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msg = str(e)
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match = re.search(r'duplicate key value violates unique constraint "'
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+table+'_(\w+)_index"', msg)
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if match: raise DuplicateKeyException(match.group(1), e)
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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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if match: raise NullValueException(match.group(1), e)
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raise # no specific exception raised
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def pkey(db, cache, table): # 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'), 0)
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return cache[table]
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def get(db, table, row, pkey, create=False, row_ct_ref=None):
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try: return value(select(db, table, [pkey], row, 1))
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except StopIteration:
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if not create: raise
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# Insert new row
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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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return value(select(db, table, [pkey], {e.col: row[e.col]}))
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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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def connect(db_config):
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db_config = db_config.copy() # don't modify input!
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module, mappings = db_engines[db_config.pop('engine')]
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for orig, new in mappings.iteritems(): util.rename_key(db_config, orig, new)
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return __import__(module).connect(**db_config)
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