DocScoDoc/ZopeProducts/ZPsycopgDA/db.py

# ZPsycopgDA/db.py - query execution
#
# Copyright (C) 2004-2010 Federico Di Gregorio  <fog@debian.org>
#
# psycopg2 is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
# License for more details.

# Import modules needed by _psycopg to allow tools like py2exe to do
# their work without bothering about the module dependencies.

from Shared.DC.ZRDB.TM import TM
from Shared.DC.ZRDB import dbi_db

from ZODB.POSException import ConflictError

import site
import pool

import psycopg2
from psycopg2.extensions import INTEGER, LONGINTEGER, FLOAT, BOOLEAN, DATE, TIME
from psycopg2.extensions import TransactionRollbackError, register_type
from psycopg2 import NUMBER, STRING, ROWID, DATETIME 


# the DB object, managing all the real query work

class DB(TM, dbi_db.DB):

    _p_oid = _p_changed = _registered = None

    def __init__(self, dsn, tilevel, typecasts, enc='utf-8'):
        self.dsn = dsn
        self.tilevel = tilevel
        self.typecasts = typecasts
        if enc is None or enc == "":
            self.encoding = "utf-8"
        else:
            self.encoding = enc
        self.failures = 0
        self.calls = 0
        self.make_mappings()

    def getconn(self, init=True):
        # if init is False we are trying to get hold on an already existing
        # connection, so we avoid to (re)initialize it risking errors.
        conn = pool.getconn(self.dsn)
        if init:
            # use set_session where available as in these versions
            # set_isolation_level generates an extra query.
            if psycopg2.__version__ >= '2.4.2':
                conn.set_session(isolation_level=int(self.tilevel))
            else:
                conn.set_isolation_level(int(self.tilevel))
            conn.set_client_encoding(self.encoding)
            for tc in self.typecasts:
                register_type(tc, conn)
        return conn

    def putconn(self, close=False):
        try:
            conn = pool.getconn(self.dsn, False)
        except AttributeError:
            pass
        pool.putconn(self.dsn, conn, close)

    def getcursor(self):
        conn = self.getconn(False)
        return conn.cursor()

    def _finish(self, *ignored):
        try:
            conn = self.getconn(False)
            conn.commit()
            self.putconn()
        except AttributeError:
            pass
            
    def _abort(self, *ignored):
        try:
            conn = self.getconn(False)
            conn.rollback()
            self.putconn()
        except AttributeError:
            pass

    def open(self):
        # this will create a new pool for our DSN if not already existing,
        # then get and immediately release a connection
        self.getconn()
        self.putconn()
        
    def close(self):
        # FIXME: if this connection is closed we flush all the pool associated
        # with the current DSN; does this makes sense?
        pool.flushpool(self.dsn)

    def sortKey(self):
        return 1

    def make_mappings(self):
        """Generate the mappings used later by self.convert_description()."""
        self.type_mappings = {}
	for t, s in [(INTEGER,'i'), (LONGINTEGER, 'i'), (NUMBER, 'n'),  
	             (BOOLEAN,'n'), (ROWID, 'i'),
	             (DATETIME, 'd'), (DATE, 'd'), (TIME, 'd')]:
            for v in t.values:
	        self.type_mappings[v] = (t, s)

    def convert_description(self, desc, use_psycopg_types=False):
        """Convert DBAPI-2.0 description field to Zope format."""
        items = []
        for name, typ, width, ds, p, scale, null_ok in desc:
	    m = self.type_mappings.get(typ, (STRING, 's'))
            items.append({
                'name': name,
                'type': use_psycopg_types and m[0] or m[1],
                'width': width,
                'precision': p,
                'scale': scale,
                'null': null_ok,
                })
        return items

    ## tables and rows ##

    def tables(self, rdb=0, _care=('TABLE', 'VIEW')):
        self._register()
        c = self.getcursor()
        c.execute(
            "SELECT t.tablename AS NAME, 'TABLE' AS TYPE "
            "  FROM pg_tables t WHERE tableowner <> 'postgres' "
            "UNION SELECT v.viewname AS NAME, 'VIEW' AS TYPE "
            "  FROM pg_views v WHERE viewowner <> 'postgres' "
            "UNION SELECT t.tablename AS NAME, 'SYSTEM_TABLE\' AS TYPE "
            "  FROM pg_tables t WHERE tableowner = 'postgres' "
            "UNION SELECT v.viewname AS NAME, 'SYSTEM_TABLE' AS TYPE "
            "FROM pg_views v WHERE viewowner = 'postgres'")
        res = []
        for name, typ in c.fetchall():
            if typ in _care:
                res.append({'TABLE_NAME': name, 'TABLE_TYPE': typ})
        self.putconn()
        return res

    def columns(self, table_name):
        self._register()
        c = self.getcursor()
        try:
            r = c.execute('SELECT * FROM "%s" WHERE 1=0' % table_name)
        except:
            return ()
        self.putconn()
        return self.convert_description(c.description, True)
    
    ## query execution ##

    def query(self, query_string, max_rows=None, query_data=None):
        self._register()
        self.calls = self.calls+1

        desc = ()
        res = []
        nselects = 0

        c = self.getcursor()

        try:
            for qs in [x for x in query_string.split('\0') if x]:
                try:
                    if query_data:
                        c.execute(qs, query_data)
                    else:
                        c.execute(qs)
                except TransactionRollbackError:
                    # Ha, here we have to look like we are the ZODB raising conflict errrors, raising ZPublisher.Publish.Retry just doesn't work
                    #logging.debug("Serialization Error, retrying transaction", exc_info=True)
                    raise ConflictError("TransactionRollbackError from psycopg2")
                except psycopg2.OperationalError:
                    #logging.exception("Operational error on connection, closing it.")
                    try:
                        # Only close our connection
                        self.putconn(True)
                    except:
                        #logging.debug("Something went wrong when we tried to close the pool", exc_info=True)
                        pass
                if c.description is not None:
                    nselects += 1
                    if c.description != desc and nselects > 1:
                        raise psycopg2.ProgrammingError(
                            'multiple selects in single query not allowed')
                    if max_rows:
                        res = c.fetchmany(max_rows)
                    else:
                        res = c.fetchall()
                    desc = c.description
            self.failures = 0

        except StandardError, err:
            self._abort()
            raise err
        
        return self.convert_description(desc), res