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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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import warnings
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import exc
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import strings
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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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##### Exceptions
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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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def _add_cursor_info(e, cur): exc.add_msg(e, 'query: '+get_cur_query(cur))
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class DbException(exc.ExceptionWithCause):
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def __init__(self, msg, cause=None, cur=None):
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exc.ExceptionWithCause.__init__(self, msg, cause)
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if cur != None: _add_cursor_info(self, cur)
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class NameException(DbException): pass
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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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468
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class DuplicateKeyException(ExceptionWithColumns): pass
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468
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class NullValueException(ExceptionWithColumns): pass
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class EmptyRowException(DbException): pass
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##### Warnings
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class DbWarning(UserWarning): pass
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##### Input validation
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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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def esc_name(db, name):
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module = util.root_module(db)
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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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elif module == 'MySQLdb': quote = '`'
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else: raise NotImplementedError("Can't escape name for "+module+' database')
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return quote + name.replace(quote, '') + quote
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##### Querying
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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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except Exception, e:
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_add_cursor_info(e, cur)
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raise
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if run_raw_query.debug:
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sys.stderr.write(strings.one_line(get_cur_query(cur))+'\n')
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return cur
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##### Recoverable querying
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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_raw_query(db, 'SAVEPOINT '+savepoint)
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try: return_val = func()
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except:
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run_raw_query(db, 'ROLLBACK TO SAVEPOINT '+savepoint)
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raise
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else:
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run_raw_query(db, 'RELEASE SAVEPOINT '+savepoint)
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return return_val
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830
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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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##### Result retrieval
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def col_names(cur): return (col[0] for col in cur.description)
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832
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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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def select(db, table, fields=None, conds=None, limit=None, start=None,
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recover=None):
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'''@param fields Use None to select all fields in the table'''
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if conds == None: conds = {}
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assert limit == None or type(limit) == int
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assert start == None or type(start) == int
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check_name(table)
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if fields != None: 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_ = esc_name(db, 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 '
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if fields == None: query += '*'
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else: query += ', '.join([esc_name(db, field) for field in fields])
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query += ' FROM '+esc_name(db, table)
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missing = True
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if conds != {}:
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query += ' WHERE '+' AND '.join(map(cond, conds.iteritems()))
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missing = False
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if limit != None: query += ' LIMIT '+str(limit); missing = False
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if start != None:
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if start != 0: query += ' OFFSET '+str(start)
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missing = False
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if missing: warnings.warn(DbWarning(
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'SELECT statement missing a WHERE, LIMIT, or OFFSET clause: '+query))
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830
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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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1554
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aaronmk
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def insert(db, table, row, returning=None, recover=None):
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'''@param returning str|None An inserted column (such as pkey) to return'''
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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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89
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query = 'INSERT INTO '+table
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89
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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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aaronmk
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if returning != None:
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check_name(returning)
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query += ' RETURNING '+returning
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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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869
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aaronmk
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return run_raw_query(db, 'TRUNCATE '+table+' CASCADE')
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832
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aaronmk
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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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1135
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aaronmk
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cache[table] = col_names(run_query(db,
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'SELECT * FROM '+table+' LIMIT 0', recover=recover)).next()
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832
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aaronmk
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return cache[table]
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853
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aaronmk
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def index_cols(db, table, index):
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'''Can also use this for UNIQUE constraints, because a UNIQUE index is
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automatically created. When you don't know whether something is a UNIQUE
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constraint or a UNIQUE index, use this function.'''
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check_name(table)
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check_name(index)
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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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866
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aaronmk
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FROM
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(
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SELECT attnum, attname
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FROM pg_index
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JOIN pg_class index ON index.oid = indexrelid
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JOIN pg_class table_ ON table_.oid = indrelid
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JOIN pg_attribute ON attrelid = indrelid AND attnum = ANY (indkey)
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WHERE
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table_.relname = %(table)s
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AND index.relname = %(index)s
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UNION
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SELECT attnum, attname
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FROM
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(
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SELECT
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indrelid
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, (regexp_matches(indexprs, E':varattno (\\\\d+)', 'g'))[1]::int
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AS indkey
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FROM pg_index
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JOIN pg_class index ON index.oid = indexrelid
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JOIN pg_class table_ ON table_.oid = indrelid
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WHERE
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table_.relname = %(table)s
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AND index.relname = %(index)s
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) s
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JOIN pg_attribute ON attrelid = indrelid AND attnum = indkey
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) s
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| 216 |
853
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aaronmk
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ORDER BY attnum
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''',
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| 218 |
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{'table': table, 'index': index})))
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else: raise NotImplementedError("Can't list index columns for "+module+
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' database')
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| 221 |
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| 222 |
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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| 234 |
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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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| 238 |
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else: raise NotImplementedError("Can't list constraint columns for "+module+
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' database')
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| 240 |
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| 241 |
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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| 243 |
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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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| 245 |
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"WHERE schemaname = 'public' ORDER BY tablename"))
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| 246 |
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elif module == 'MySQLdb': return values(run_query(db, 'SHOW TABLES'))
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| 247 |
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else: raise NotImplementedError("Can't list tables for "+module+' database')
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| 248 |
830
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aaronmk
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| 249 |
833
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aaronmk
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##### Database management
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| 250 |
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| 251 |
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def empty_db(db):
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| 252 |
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for table in tables(db): truncate(db, table)
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| 253 |
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| 254 |
832
|
aaronmk
|
##### Heuristic queries
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| 255 |
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| 256 |
1554
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aaronmk
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def try_insert(db, table, row, returning=None):
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| 257 |
830
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aaronmk
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'''Recovers from errors'''
|
| 258 |
1554
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aaronmk
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try: return insert(db, table, row, returning, recover=True)
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| 259 |
46
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aaronmk
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except Exception, e:
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| 260 |
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msg = str(e)
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| 261 |
465
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aaronmk
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match = re.search(r'duplicate key value violates unique constraint '
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| 262 |
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r'"(([^\W_]+)_[^"]+)"', msg)
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| 263 |
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if match:
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| 264 |
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constraint, table = match.groups()
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| 265 |
854
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aaronmk
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try: cols = index_cols(db, table, constraint)
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| 266 |
465
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aaronmk
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except NotImplementedError: raise e
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| 267 |
851
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aaronmk
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else: raise DuplicateKeyException(cols, e)
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| 268 |
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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| 269 |
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'constraint', msg)
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| 270 |
470
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aaronmk
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if match: raise NullValueException([match.group(1)], e)
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| 271 |
13
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aaronmk
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raise # no specific exception raised
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| 272 |
11
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aaronmk
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| 273 |
471
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aaronmk
|
def put(db, table, row, pkey, row_ct_ref=None):
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| 274 |
1554
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aaronmk
|
'''Recovers from errors.
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| 275 |
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Only works under PostgreSQL (uses `INSERT ... RETURNING`)'''
|
| 276 |
471
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aaronmk
|
try:
|
| 277 |
1554
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aaronmk
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cur = try_insert(db, table, row, pkey)
|
| 278 |
|
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if row_ct_ref != None and cur.rowcount >= 0:
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| 279 |
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row_ct_ref[0] += cur.rowcount
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| 280 |
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return value(cur)
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| 281 |
471
|
aaronmk
|
except DuplicateKeyException, e:
|
| 282 |
1069
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aaronmk
|
return value(select(db, table, [pkey],
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| 283 |
|
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util.dict_subset_right_join(row, e.cols), recover=True))
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| 284 |
471
|
aaronmk
|
|
| 285 |
473
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aaronmk
|
def get(db, table, row, pkey, row_ct_ref=None, create=False):
|
| 286 |
830
|
aaronmk
|
'''Recovers from errors'''
|
| 287 |
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try: return value(select(db, table, [pkey], row, 1, recover=True))
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| 288 |
14
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aaronmk
|
except StopIteration:
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| 289 |
40
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aaronmk
|
if not create: raise
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| 290 |
471
|
aaronmk
|
return put(db, table, row, pkey, row_ct_ref) # insert new row
|
| 291 |
131
|
aaronmk
|
|
| 292 |
832
|
aaronmk
|
##### Database connections
|
| 293 |
|
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|
| 294 |
131
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aaronmk
|
db_engines = {
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| 295 |
|
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'MySQL': ('MySQLdb', {'password': 'passwd', 'database': 'db'}),
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| 296 |
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'PostgreSQL': ('psycopg2', {}),
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| 297 |
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}
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| 298 |
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| 299 |
360
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aaronmk
|
DatabaseErrors_set = set([DbException])
|
| 300 |
|
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DatabaseErrors = tuple(DatabaseErrors_set)
|
| 301 |
342
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aaronmk
|
|
| 302 |
|
|
def _add_module(module):
|
| 303 |
|
|
DatabaseErrors_set.add(module.DatabaseError)
|
| 304 |
|
|
global DatabaseErrors
|
| 305 |
|
|
DatabaseErrors = tuple(DatabaseErrors_set)
|
| 306 |
|
|
|
| 307 |
646
|
aaronmk
|
def connect(db_config, serializable=True):
|
| 308 |
131
|
aaronmk
|
db_config = db_config.copy() # don't modify input!
|
| 309 |
342
|
aaronmk
|
module_name, mappings = db_engines[db_config.pop('engine')]
|
| 310 |
|
|
module = __import__(module_name)
|
| 311 |
|
|
_add_module(module)
|
| 312 |
330
|
aaronmk
|
for orig, new in mappings.iteritems():
|
| 313 |
|
|
try: util.rename_key(db_config, orig, new)
|
| 314 |
|
|
except KeyError: pass
|
| 315 |
646
|
aaronmk
|
db = module.connect(**db_config)
|
| 316 |
|
|
if serializable:
|
| 317 |
830
|
aaronmk
|
run_raw_query(db, 'SET TRANSACTION ISOLATION LEVEL SERIALIZABLE')
|
| 318 |
646
|
aaronmk
|
return db
|
| 319 |
|
|
|
| 320 |
|
|
def db_config_str(db_config):
|
| 321 |
|
|
return db_config['engine']+' database '+db_config['database']
|
