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database.py

00001 """ Main entry point for gadfly sql.

:Author: Aaron Watters
:Maintainers: http://gadfly.sf.net/
:Copyright: Aaron Robert Watters, 1994
:Id: $Id: database.py,v 1.7 2002/05/14 23:52:54 richard Exp $:
"""

error = "gadfly_error"
verbosity = 0

from store import Database0, File_Storage0, Transaction_Logger

00014 class gadfly:
    """as per the DBAPI spec "gadfly" is the connection object."""
    closed = 0
    verbose = verbosity # debug!

    # this will be loaded on first instance creation
    sql = None

    def __init__(self, databasename=None, directory=None, forscratch=0,
             autocheckpoint=1, verbose=0):
        # on first gadfly usage, load up the SQL grammar
        if self.sql is None:
            from gadfly import sql, bindings
            sql = sql.getSQL()
            self.sql = bindings.BindRules(sql)

        verbose = self.verbose = self.verbose or verbose
        # checkpoint on each commit if set
        self.autocheckpoint = autocheckpoint
        if verbose:
            print "initializing gadfly instance", databasename, directory, \
                forscratch
        self.is_scratch = forscratch
        self.databasename = databasename
        self.directory = directory
        self.fs = None
        self.database = None
        # db global transaction id
        self.transid = 0
        if databasename is not None:
            self.open()

    def transaction_log(self):
        if self.verbose:
            print "new transaction log for", `self.database.log`, self.transid
        return Transaction_Logger(self.database.log, self.transid,
             self.is_scratch)

00052     def checkpoint(self):
        """permanently record committed updates"""
        # note: No transactions should be active at checkpoint for this implementation!
        # implicit abort of active transactions!
        verbose = self.verbose
        if verbose:
            print "checkpointing gadfly instance", self.databasename
        db = self.database
        log = db.log
        # dump committed db to fs
        fs = self.fs
        if fs and db and not db.is_scratch:
            # flush the log
            if log:
                if verbose: print "gadfly: committing log"
                log.commit()
            elif verbose:
                print "gadfly: no log to commit"
            if verbose: print "gadfly: dumping mutated db structures"
            fs.dump(db)
        elif verbose:
            print "gadfly: no checkpoint required"
        if verbose:
            print "gadfly: new transid, reshadowing"
        self.transid = self.transid+1
        self.working_db.reshadow(db, self.transaction_log())

    def startup(self, databasename, directory, scratch=0, verbose=0):
        verbose = self.verbose
        if verbose:
            print "gadfly: starting up new ", databasename, directory, scratch
        if self.database:
            raise error, "cannot startup, database bound"
        self.databasename = databasename
        self.directory = directory
        db = self.database = Database0()
        db.is_scratch = scratch or self.is_scratch
        if verbose:
            print 'gadfly.startup: new working_db'
        self.fs = File_Storage0(databasename, directory)
        self.working_db = Database0(db, self.transaction_log())
        # commit initializes database files and log structure
        if verbose:
            print 'gadfly.startup: commit'
        self.commit()
        # for now: all transactions serialized
        #  working db shared among all transactions/cursors
        self.transid = self.transid+1
        if verbose:
            print 'gadfly.startup: new working_db'
        self.working_db = Database0(db, self.transaction_log())

00104     def restart(self):
        """Reload and rerun committed updates from log, discard uncommitted
        """
        # mainly for testing recovery.
        if self.verbose:
            print "gadfly: restarting database", self.databasename
        self.database.clear()
        if self.working_db is not None:
            self.working_db.clear()
        self.working_db = None
        self.database = None
        self.open()

00117     def open(self):
        """ (re)load existing database
        """
        if self.verbose:
            print "gadfly: loading database", self.databasename
        if self.directory:
            directory = self.directory
        else:
            directory = "."
        fs = self.fs = File_Storage0(self.databasename, directory)
        db = self.database = fs.load() #self.sql)
        self.transid = self.transid+1
        self.working_db = Database0(db, self.transaction_log())
        self.commit()

00132     def add_remote_view(self, name, definition):
        """add a remote view to self.
           Must be redone on each reinitialization!
           Must not recursively reenter the query evaluation process for
           this database!
           "Tables" added in this manner cannot be update via SQL.
        """
        self.database[name] = definition
        self.working_db[name] = definition

00142     def close(self):
        """checkpoint and clear the database"""
        if self.closed: return
        if self.verbose:
            print "gadfly: closing database", self.databasename
        db = self.database
        if not db.is_scratch:
            self.checkpoint()
        if db: db.clear()
        wdb = self.working_db
        if wdb:
            wdb.clear()
        self.working_db = None
        self.closed = 1

00157     def commit(self):
        """Commit the working database+transaction, flush log, new transid
        """
        verbose = self.verbose
        autocheckpoint = self.autocheckpoint
        if self.verbose:
            print "gadfly: committing", self.transid, self.databasename
        self.transid = self.transid+1
        fs = self.fs
        db = self.database
        wdb = self.working_db
        if not wdb:
            # no working database
            return
        wdblog = wdb.log
        if wdblog:
            if self.verbose:
                print "gadfly: committing working_db", wdblog
            wdblog.commit(verbose=self.verbose)
        wdb.commit()
        if fs and db and not db.is_scratch:
            if autocheckpoint:
                if verbose:
                    print "gadfly: autocheckpoint"
                # skips a transid?
                self.checkpoint()
            else:
                if verbose:
                    print "gadfly: no autocheckpoint"
                wdb.reshadow(db, self.transaction_log())
        else:
            if verbose:
                print "gadfly: scratch db, no logging, just reshadow"
            wdb.reshadow(db, self.transaction_log())

00192     def rollback(self):
        """discard the working db, new transid, recreate working db"""
        verbose = self.verbose
        if verbose:
            print "gadfly: rolling back", self.transid, self.databasename
        if not (self.fs or self.database):
            raise error, "unbound, cannot rollback"
        # discard updates in working database
        self.working_db.clear()
        self.transid = self.transid+1
        self.working_db.reshadow(self.database, self.transaction_log())
        #self.open()

    def cursor(self):
        if self.verbose:
            print "gadfly: new cursor", self.databasename
        db = self.database
        if db is None:
            raise error, "not bound to database"
        return GF_Cursor(self)

    def dumplog(self):
        log = self.database.log
        if log:
            log.dump()
        else:
            print "no log to dump"

    def table_names(self):
        return self.working_db.relations()

    def DUMP_ALL(self):
        print "DUMPING ALL CONNECTION DATA", self.databasename, self.directory
        print
        print "***** BASE DATA"
        print
        print self.database
        print
        print "***** WORKING DATA"
        print
        print self.working_db


class GF_Cursor:

    verbose = verbosity

    arraysize = None

    description = None

    EVAL_DUMP = 0 # only for extreme debugging!

    def __init__(self, gadfly_instance):
        verbose = self.verbose = self.verbose or gadfly_instance.verbose
        if verbose:
            print "GF_Cursor.__init__", id(self)
        self.connection = gadfly_instance
        self.results = None
        self.resultlist = None
        self.statement = None
        # make a shadow of the shadow db! (in case of errors)
        self.shadow_db = Database0()
        self.reshadow()
        self.connection = gadfly_instance

    def reshadow(self):
        if self.verbose:
            print "GF_Cursor.reshadow", id(self)
        db = self.connection.working_db
        shadow = self.shadow_db
        shadow.reshadow(db, db.log)
        if self.verbose:
            print "rels", shadow.rels.keys()

    def close(self):
        if self.verbose:
            print "GF_Cursor.close", id(self)
        self.connection = None

    def reset_results(self):
        if self.verbose:
            print "GF_Cursor.reset_results", id(self)
        rs = self.results
        if rs is None:
            raise error, "must execute first"
        if len(rs)!=1:
            raise error, "cannot retrieve multiple results"
        rel = rs[0]
        rows = rel.rows()
        atts = rel.attributes()
        tupatts = tuple(atts)
        resultlist = list(rows)
        if len(tupatts)==1:
            att = tupatts[0]
            for i in xrange(len(resultlist)):
                resultlist[i] = (resultlist[i][att],)
        else:
            for i in xrange(len(resultlist)):
                resultlist[i] = resultlist[i].dump(tupatts)
        self.resultlist = resultlist

    def fetchone(self):
        if self.verbose:
            print "GF_Cursor.fetchone", id(self)
        r = self.resultlist
        if r is None:
            self.reset_results()
            r = self.resultlist
        if len(r)<1:
            raise error, "no more results"
        result = r[0]
        del r[0]
        return result

    def fetchmany(self, size=None):
        if self.verbose:
            print "GF_Cursor.fetchmany", id(self)
        r = self.resultlist
        if r is None:
            self.reset_results()
            r = self.resultlist
        if size is None:
            size = len(r)
        result = r[:size]
        del r[:size]
        return result

    def fetchall(self):
        if self.verbose:
            print "GF_Cursor.fetchall", id(self)
        return self.fetchmany()

    def execute(self, statement=None, params=None):
        """execute operations, commit results if no error"""
        success = 0
        verbose = self.verbose
        if verbose:
            print "GF_Cursor.execute", id(self)
        if statement is None and self.statement is None:
            raise error, "cannot execute, statement not bound"
        if statement!=self.statement:
            if verbose: print "GF_cursor: new statement: parsing"
            # only reparse on new statement.
            self.statement=statement
            from semantics import Parse_Context
            context = Parse_Context()
            cs = self.commands = self.connection.sql.DoParse1(statement, context)
        else:
            if verbose: print "GF_cursor: old statment, not parsing"
            cs = self.commands
        # always rebind! (db may have changed)
        if verbose: print "GF_Cursor: binding to temp db"
        # make a new shadow of working db
        # (should optimize?)
        self.reshadow()
        # get shadow of working database
        database = self.shadow_db
        if self.EVAL_DUMP:
            print "***"
            print "*** dumping connection parameters before eval"
            print "***"
            print "*** eval scratch db..."
            print
            print database
            print
            print "*** connection data"
            print
            self.connection.DUMP_ALL()
            print "********** end of eval dump"
        for i in xrange(len(cs)):
            if verbose:
                print "GFCursor binding\n", cs[i]
                print database.rels.keys()
            cs[i] = cs[i].relbind(database)
        cs = self.commands
        self.results = results = list(cs)
        # only unshadow results on no error
        try:
            for i in xrange(len(cs)):
                results[i] = cs[i].eval(params)
            success = 1
        finally:
            #print "in finally", success
            # only on no error...
            if success:
                # commit updates in shadow of working db (not in real db)
                if verbose: print "GFCursor: successful eval, storing results in wdb"
                database.log.flush()
                # database commit does not imply transaction commit.
                database.commit()
            else:
                if verbose:
                    print \
    "GFCursor: UNSUCCESSFUL EVAL, discarding results and log entries"
                self.statement = None
                self.results = None
                self.resultlist = None
                database.log.reset()
        # handle curs.description
        self.description = None
        if len(results)==1:
            result0 = results[0]
            try:
                atts = result0.attributes()
            except:
                pass
            else:
                descriptions = list(atts)
                fluff = (None,) * 6
                for i in xrange(len(atts)):
                    descriptions[i] = (atts[i],) + fluff
                self.description = tuple(descriptions)
        self.resultlist = None

    def setoutputsize(self, *args):
        # not implemented
        pass

    def setinputsizes(self, *args):
        # not implemented
        pass

    def pp(self):
        """return pretty-print string rep of current results"""
        from string import join
        stuff = map(repr, self.results)
        return join(stuff, "\n\n")

#
# $Log: database.py,v $
# Revision 1.7  2002/05/14 23:52:54  richard
# - fixed commit-after-open bug (no working_db)
# - added more functionality to gfplus:
#   / or !!         repeat last command (blank line does the same thing)
#   (s|c)/pat/repl  repeat last but RE sub pat for repl
# - corrected gfplus exit code
#
# Revision 1.6  2002/05/11 02:59:04  richard
# Added info into module docstrings.
# Fixed docco of kwParsing to reflect new grammar "marshalling".
# Fixed bug in gadfly.open - most likely introduced during sql loading
# re-work (though looking back at the diff from back then, I can't see how it
# wasn't different before, but it musta been ;)
# A buncha new unit test stuff.
#
# Revision 1.5  2002/05/08 00:49:00  anthonybaxter
# El Grande Grande reindente! Ran reindent.py over the whole thing.
# Gosh, what a lot of checkins. Tests still pass with 2.1 and 2.2.
#
# Revision 1.4  2002/05/08 00:31:52  richard
# More cleanup.
#
# Revision 1.3  2002/05/07 23:19:02  richard
# Removed circular import (at import time at least)
#
# Revision 1.2  2002/05/07 07:06:11  richard
# Cleaned up sql grammar compilation some more.
# Split up the BigList into its components too.
#
# Revision 1.1.1.1  2002/05/06 07:31:09  richard
#
#
#

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