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import sqlalchemy

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from sqlalchemy import *

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import logging; log = logging.getLogger('pvl.verkko.db')

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# schema

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metadata = MetaData()

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dhcp_hosts = Table('dhcp_hosts', metadata,

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    Column('id',            Integer,    primary_key=True),

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    # unique

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    Column('ip',            String,     nullable=False),

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    Column('mac',           String,     nullable=False),

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    Column('gw',            String,     nullable=False),

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    # updated

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    Column('first_seen',    DateTime,   nullable=False),

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    Column('last_seen',     DateTime,   nullable=False),

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    # scalar; updated

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    Column('name',          String,     nullable=True),

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    Column('state',         String,     nullable=True),

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    Column('error',         String,     nullable=True),

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    # counters

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    Column('count',         Integer,    default=1),

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    UniqueConstraint('ip', 'mac', 'gw'),

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)

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dhcp_leases = Table('dhcp_leases', metadata,

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    Column('id',            Integer,    primary_key=True),

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    Column('ip',            String,     nullable=False),

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    Column('mac',           String,     nullable=False),

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    Column('hostname',      String,     nullable=True),

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    Column('starts',        DateTime,   nullable=False),

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    Column('ends',          DateTime,   nullable=True),  # never

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    Column('state',         String,     nullable=True),

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    Column('next',          String,     nullable=True),

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)

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# for ORM models

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from sqlalchemy.orm import mapper, sessionmaker

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Session = sessionmaker()

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class Database (object) :

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    """

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        Our underlying database.

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    """

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    def __init__ (self, database) :

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        """

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            database        - sqlalchemy connection URI

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        """

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        self.engine = create_engine(database, 

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            echo    = (log.isEnabledFor(logging.DEBUG)),

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        )

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    # ORM

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    def session (self) :

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        """

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            Return a new ORM session bound to our engine.

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            XXX: session lifetimes? Explicit close?

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        """

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        return Session(bind=self.engine)

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    # SQL

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    def connect (self) :

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        return self.engine.connect()

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    def execute (self, query) :

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        return self.engine.execute(query)

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    def select (self, query) :

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        return self.engine.execute(query)

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    def get (self, query) :

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        """

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            Fetch a single row.

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            XXX: returning None if not found

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        """

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        return self.select(query).fetchone()

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    def insert (self, insert) :

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        """

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            Execute given INSERT query, returning the inserted primary key.

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        """

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        result = self.engine.execute(insert)

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        id, = result.inserted_primary_key

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        return id

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    def update (self, update) :

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        """

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            Execute given UPDATE query, returning the number of matched rows.

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        """

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        result = self.engine.execute(update)

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        return result.rowcount

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