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db.py

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'''$Id: db.py 532 2008-03-18 20:37:48Z eikenberry $'''
__version__='$Revision: 532 $'[11:-2]

import _mysql
import MySQLdb
from _mysql_exceptions import (OperationalError, NotSupportedError,
        ProgrammingError)
MySQLdb_version_required = (1,2,0)

try:
    MySQLdb_version = MySQLdb.version_info[:3]
except AttributeError:
    MySQLdb_version = getattr(_mysql, 'version_info', (0,0,0))

if MySQLdb_version < MySQLdb_version_required:
    raise NotSupportedError, \
        "ZMySQLDA requires at least MySQLdb %s, %s found" % \
        (MySQLdb_version_required, _v)

from MySQLdb.converters import conversions
from MySQLdb.constants import FIELD_TYPE, CR, ER, CLIENT, FLAG
from ZODB.POSException import ConflictError
from DateTime import DateTime

from thread import get_ident, allocate_lock
import logging
LOG = logging.getLogger('ZMySQLDA')
from joinTM import joinTM

hosed_connection = (
    CR.SERVER_GONE_ERROR,
    CR.SERVER_LOST
    )

query_syntax_error = (
    ER.BAD_FIELD_ERROR,
    )

key_types = {
    "PRI": "PRIMARY KEY",
    "MUL": "INDEX",
    "UNI": "UNIQUE",
    }

field_icons = "bin", "date", "datetime", "float", "int", "text", "time"

icon_xlate = {
    "varchar": "text", "char": "text",
    "enum": "what", "set": "what",
    "double": "float", "numeric": "float",
    "blob": "bin", "mediumblob": "bin", "longblob": "bin",
    "tinytext": "text", "mediumtext": "text",
    "longtext": "text", "timestamp": "datetime",
    "decimal": "float", "smallint": "int",
    "mediumint": "int", "bigint": "int",
    }

type_xlate = {
    "double": "float", "numeric": "float",
    "decimal": "float", "smallint": "int",
    "mediumint": "int", "bigint": "int",
    "int": "int", "float": "float",
    "timestamp": "datetime", "datetime": "datetime",
    "time": "datetime",
    }
    
def _mysql_timestamp_converter(s):
    if len(s) < 14:
        s = s + "0"*(14-len(s))
        parts = map(int, (s[:4],s[4:6],s[6:8],
                          s[8:10],s[10:12],s[12:14]))
    return DateTime("%04d-%02d-%02d %02d:%02d:%02d" % tuple(parts))

def DateTime_or_None(s):
    try: return DateTime(s)
    except: return None

def int_or_long(s):
    try: return int(s)
    except: return long(s)


00168 class DBPool(object):
    """
      This class is an interface to DB.
      Its caracteristic is that an instance of this class interfaces multiple
      instanes of DB class, each one being bound to a specific thread.
    """

    connected_timestamp = ''
    _create_db          = False
    use_unicode         = False

00179     def __init__(self, db_cls, create_db=False, use_unicode=False):
        """ Set transaction managed DB class for use in pool.
        """
        self.DB = db_cls
        # pool of one db object/thread
        self._db_pool = {}
        self._db_lock = allocate_lock()
        # auto-create db if not present on server
        self._create_db = create_db
        # unicode settings
        self.use_unicode = use_unicode

00191     def __call__(self, connection):
        """ Parse the connection string.

            Initiate a trial connection with the database to check
            transactionality once instead of once per DB instance.

            Create database if option is enabled and database doesn't exist.
        """
        self.connection = connection
        DB = self.DB
        #
        db_flags = DB._parse_connection_string(connection, self.use_unicode)
        self._db_flags = db_flags

        # connect to server to determin tranasactional capabilities
        # can't use DB instance as it requires this information to work
        try:
            connection = MySQLdb.connect(**db_flags['kw_args'])
        except OperationalError:
            if self._create_db:
                kw_args = db_flags.get('kw_args',{}).copy()
                db = kw_args.pop('db',None)
                if not db: raise
                connection = MySQLdb.connect(**kw_args)
                create_query = "create database %s" % db
                if self.use_unicode:
                    create_query += (" default character set %s"
                            % DB.unicode_charset)
                connection.query(create_query)
                connection.store_result()
            else:
                raise
        transactional = connection.server_capabilities & CLIENT.TRANSACTIONS
        connection.close()

        # Some tweaks to transaction/locking db_flags based on server setup
        if db_flags['try_transactions'] == '-':
            transactional = False
        elif not transactional and db_flags['try_transactions'] == '+':
            raise NotSupportedError, "transactions not supported by this server"
        db_flags['transactions'] = transactional
        del db_flags['try_transactions']
        if transactional or db_flags['mysql_lock']:
            db_flags['use_TM'] = True

        # will not be 100% accurate in regard to per thread connections
        # but as close as we're going to get it.
        self.connected_timestamp = DateTime()

        # return self as the database connection object 
        # (assigned to _v_database_connection)
        return self

00244     def closeConnection(self):
        """ Close this threads connection. Used when DA is being reused
            but the connection string has changed. Need to close the DB
            instances and recreate to the new database. Only have to worry
            about this thread as when each thread hits the new connection
            string in the DA this method will be called.
        """
        ident = get_ident()
        try:
            self._pool_del(ident)
        except KeyError:
            pass

00257     def close(self):
        """ Used when manually closing the database. Resetting the pool
            dereferences the DB instances where they are then collected
            and closed.
        """
        self._db_pool = {}

00264     def _pool_set(self, key, value):
        """ Add a db to pool.
        """
        self._db_lock.acquire()
        try:
            self._db_pool[key] = value
        finally:
            self._db_lock.release()

00273     def _pool_get(self, key):
        """ Get db from pool. Read only, no lock necessary.
        """
        return self._db_pool.get(key)

00278     def _pool_del(self, key):
        """ Remove db from pool.
        """
        self._db_lock.acquire()
        try:
            del self._db_pool[key]
        finally:
            self._db_lock.release()

00287     def name(self):
        """ Return name of database connected to.
        """
        return self._db_flags['kw_args']['db']

    # Passthrough aliases for methods on DB class.
    def variables(self, *args, **kw):
        return self._access_db(method_id='variables', args=args, kw=kw)

    def tables(self, *args, **kw):
        return self._access_db(method_id='tables', args=args, kw=kw)

    def columns(self, *args, **kw):
        return self._access_db(method_id='columns', args=args, kw=kw)

    def query(self, *args, **kw):
        return self._access_db(method_id='query', args=args, kw=kw)

    def string_literal(self, *args, **kw):
        return self._access_db(method_id='string_literal', args=args, kw=kw)

    def unicode_literal(self, *args, **kw):
        return self._access_db(method_id='unicode_literal', args=args, kw=kw)

00311     def _access_db(self, method_id, args, kw):
        """
          Generic method to call pooled objects' methods.
          When the current thread had never issued any call, create a DB
          instance.
        """
        ident = get_ident()
        db = self._pool_get(ident)
        if db is None:
            db = self.DB(**self._db_flags)
            self._pool_set(ident, db)
        return getattr(db, method_id)(*args, **kw)


class DB(joinTM):

    Database_Error=_mysql.Error

    defs={
        FIELD_TYPE.CHAR: "i", FIELD_TYPE.DATE: "d",
        FIELD_TYPE.DATETIME: "d", FIELD_TYPE.DECIMAL: "n",
        FIELD_TYPE.DOUBLE: "n", FIELD_TYPE.FLOAT: "n", FIELD_TYPE.INT24: "i",
        FIELD_TYPE.LONG: "i", FIELD_TYPE.LONGLONG: "l",
        FIELD_TYPE.SHORT: "i", FIELD_TYPE.TIMESTAMP: "d",
        FIELD_TYPE.TINY: "i", FIELD_TYPE.YEAR: "i",
        }

    conv=conversions.copy()
    conv[FIELD_TYPE.LONG] = int_or_long
    conv[FIELD_TYPE.DATETIME] = DateTime_or_None
    conv[FIELD_TYPE.DATE] = DateTime_or_None
    conv[FIELD_TYPE.DECIMAL] = float
    del conv[FIELD_TYPE.TIME]
    # compatibility/fix for older mysqldb versions
    # without this you can get character arrays for some values
    # eg. group_concat()
    if MySQLdb_version < (1, 2, 2):
        conv[FIELD_TYPE.BLOB][0] = (FLAG.BINARY, str)

    _p_oid=_p_changed=_registered=None

    unicode_charset    = 'utf8' # hardcoded for now

    def __init__(self, connection=None, kw_args=None, use_TM=None,
            mysql_lock=None, transactions=None):
        self.connection     = connection # backwards compat
        self._kw_args       = kw_args
        self._mysql_lock    = mysql_lock
        self._use_TM        = use_TM
        self._transactions  = transactions
        self._forceReconnection()

    def close(self):
        """ Close connection and dereference.
        """
        if getattr(self,'db',None):
            self.db.close()
            self.db = None
    __del__ = close

    def _forceReconnection(self):
        """ (Re)Connect to database.
        """
        try: # try to clean up first
            self.db.close()
        except: pass
        self.db = MySQLdb.connect(**self._kw_args)
        # Newer mysqldb requires ping argument to attmept a reconnect.
        # This setting is persistent, so only needed once per connection.
        if MySQLdb_version >= (1, 2, 2):
            self.db.ping(True)

    @classmethod
    def _parse_connection_string(cls, connection, use_unicode=False):
        """ Done as a class method to both allow access to class attribute
            conv (conversion) settings while allowing for wrapping pool class
            use of this method. The former is important to allow for subclasses
            to override the conv settings while the latter is important so 
            the connection string doesn't have to be parsed for each instance
            in the pool.
        """
        kw_args = {'conv':cls.conv}
        flags = {'kw_args':kw_args, 'connection':connection}
        if use_unicode:
            kw_args['use_unicode'] = use_unicode
            kw_args['charset']     = cls.unicode_charset
        items = connection.split()
        flags['use_TM'] = None
        if _mysql.get_client_info()[0] >= '5':
            kw_args['client_flag'] = CLIENT.MULTI_STATEMENTS
        if items:
            lockreq, items = items[0], items[1:]
            if lockreq[0] == "*":
                flags['mysql_lock'] = lockreq[1:]
                db_host, items = items[0], items[1:]
                flags['use_TM'] = True # redundant. eliminate?
            else:
                flags['mysql_lock'] = None
                db_host = lockreq
            if '@' in db_host:
                db, host = db_host.split('@',1)
                kw_args['db'] = db
                if ':' in host:
                    host, port = host.split(':',1)
                    kw_args['port'] = int(port)
                kw_args['host'] = host
            else:
                kw_args['db'] = db_host
            if kw_args['db'] and kw_args['db'][0] in ('+', '-'):
                flags['try_transactions'] = kw_args['db'][0]
                kw_args['db'] = kw_args['db'][1:]
            else:
                flags['try_transactions'] = None
            if not kw_args['db']:
                del kw_args['db']
            if items:
                kw_args['user'], items = items[0], items[1:]
            if items:
                kw_args['passwd'], items = items[0], items[1:]
            if items:
                kw_args['unix_socket'], items = items[0], items[1:]

        return flags

    def tables(self, rdb=0,
               _care=('TABLE', 'VIEW')):
        """ Returns list of tables.
        """
        r=[]
        a=r.append
        result = self._query("SHOW TABLES")
        row = result.fetch_row(1)
        while row:
            table_name = row[0][0]
            a({'table_name': table_name, 'table_type': 'table'})
            row = result.fetch_row(1)
        return r

    def columns(self, table_name):
        """ Returns list of columns for [table_name].
        """
        try:
            # Field, Type, Null, Key, Default, Extra
            c = self._query('SHOW COLUMNS FROM %s' % table_name)
        except:
            return ()
        r=[]
        for Field, Type, Null, Key, Default, Extra in c.fetch_row(0):
            info = {}
            field_default = ''
            if Default is not None:
                info['default'] = Default
                field_default = "DEFAULT '%s'" % Default
            if '(' in Type:
                end = Type.rfind(')')
                short_type, size = Type[:end].split('(',1)
                if short_type not in ('set','enum'):
                    if ',' in size:
                        info['scale'], info['precision'] = \
                                       map(int, size.split(',',1))
                    else:
                        info['scale'] = int(size)
            else:
                short_type = Type
            if short_type in field_icons:
                info['icon'] = short_type
            else:
                info['icon'] = icon_xlate.get(short_type, "what")
            info['name'] = Field
            info['type'] = short_type
            info['extra'] = Extra,
            info['description'] = ' '.join([Type, field_default, Extra or '',
                                        key_types.get(Key, Key or ''),
                                        Null != 'NULL' and 'NOT NULL' or ''])
            info['nullable'] = (Null == 'YES') and 1 or 0
            if Key:
                info['index'] = True
                info['key'] = Key
            if Key == 'PRI':
                info['primary_key'] = True
                info['unique'] = True
            elif Key == 'UNI':
                info['unique'] = True
            r.append(info)
        return r

    def variables(self):
        """ Return dictionary of current mysql variable/values.
        """
        # variable_name, value
        variables = self._query('SHOW VARIABLES')
        return dict((name, value) for name, value in variables.fetch_row(0))

    def _query(self, query, force_reconnect=False):
        """
          Send a query to MySQL server.
          It reconnects automaticaly if needed and the following conditions are
          met:
           - It has not just tried to reconnect (ie, this function will not
             attempt to connect twice per call).
           - This conection is not transactionnal and has set no MySQL locks,
             because they are bound to the connection. This check can be
             overridden by passing force_reconnect with True value.
        """
        try:
            self.db.query(query)
        except OperationalError, m:
            if m[0] in query_syntax_error:
                raise OperationalError(m[0], '%s: %s' % (m[1], query))
            if ((not force_reconnect) and \
                    (self._mysql_lock or self._transactions)) or \
                    m[0] not in hosed_connection:
                LOG.warning('query failed: %s' % (query,))
                raise
            # Hm. maybe the db is hosed.  Let's restart it.
            self._forceReconnection()
            self.db.query(query)
        except ProgrammingError:
            LOG.warning('query failed: %s' % (query,))
            raise
        return self.db.store_result()

    def query(self, query_string, max_rows=1000):
        """ API method for making the query to mysql.
        """
        self._use_TM and self._register()
        desc=None
        result=()
        for qs in filter(None, [q.strip() for q in query_string.split('\0')]):
            qtype = qs.split(None, 1)[0].upper()
            if qtype == "SELECT" and max_rows:
                qs = "%s LIMIT %d" % (qs,max_rows)
                r=0
            c = self._query(qs)
            if desc is not None:
                if c and (c.describe() != desc):
                    raise ProgrammingError(
                        'Multiple select schema are not allowed'
                        )
            if c:
                desc=c.describe()
                result=c.fetch_row(max_rows)
            else:
                desc=None

        if desc is None: return (),()

        items=[]
        func=items.append
        defs=self.defs
        for d in desc:
            item={'name': d[0],
                  'type': defs.get(d[1],"t"),
                  'width': d[2],
                  'null': d[6]
                 }
            func(item)
        return items, result

    def string_literal(self, s):
        """ Called from zope to quote/escape strings for inclusion
            in a query.
        """
        return self.db.string_literal(s)

    def unicode_literal(self, s):
        """ Similar to string_literal but encodes it first.
        """
        return self.db.unicode_literal(s)

    # Zope 2-phase transaction handling methods
    def _begin(self, *ignored):
        """ Called from _register() upon first query.
        """
        try:
            self._transaction_begun = True
            self.db.ping()
            if self._transactions:
                self._query("BEGIN")
            if self._mysql_lock:
                self._query("SELECT GET_LOCK('%s',0)" % self._mysql_lock)
        except:
            LOG.error("exception during _begin", exc_info=True)
            raise ConflictError

    def _finish(self, *ignored):
        """ Called as final event in transaction system.
        """
        if not self._transaction_begun:
            return
        self._transaction_begun = False
        try:
            if self._mysql_lock:
                self._query("SELECT RELEASE_LOCK('%s')" % self._mysql_lock)
            if self._transactions:
                self._query("COMMIT")
        except:
            LOG.error("exception during _finish", exc_info=True)
            raise ConflictError

    def _abort(self, *ignored):
        """ Called in case of transactional error.
        """
        if not self._transaction_begun:
            return
        self._transaction_begun = False
        if self._mysql_lock:
            self._query("SELECT RELEASE_LOCK('%s')" % self._mysql_lock)
        if self._transactions:
            self._query("ROLLBACK")
        else:
            LOG.error("aborting when non-transactional")


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