[pybsddb] BDB Indexing and Joined Cursor issue

[Sury Soni]

Since, I am using indexes (secondary databases), I need to make sure, if
there are records in each (secondary database) cursor. So as per your
suggestion, I started with using count(), later changed to
get_current_size().

Following the function, I am using to find join()'ed cursor of all
secondary database, based on filter queries for each secondary database.

    def search(self, pattern):
        queries = splitKey(pattern)

        print "Queries: ", queries
        print "Secondary database count: ", len(self.dbs)

        try:
            if len(self.dbs)>0:
                curs = []
                i=0
                # Iterate over all the secondary index databases to get
individual
                # cursors and join to get final filter from primary
database.
                # self.dbs is array of all secondary database handles
                for dbsi in self.dbs:
                    try:
                        if i>(len(queries)-1):
                            break
                        cur = dbsi.cursor()
                        if queries[i].find("x")<0:
                            cur.pget(key=queries[i], flags=DB_SET_RANGE)
                            try:
                                if cur.get_current_size()>0:
## previously ##  if cur.count()>0:
                                    curs.append(cur)
                                else:
                                    cur.close()
                            except Exception, e:
                                print "Exception in get current size: ",
e
                                traceback.print_exc(file=sys.stdout)
                                cur.close()
                        i+=1
                    except Exception, e:
                        print "Exception in search, case 0: ", e
                        traceback.print_exc(file=sys.stdout)
                        raise NextDigital.DBEOFException()

                # checking, if enough secondary database handle
available to be joined!
                if len(curs)<=0:
                    raise NextDigital.DBEOFException()

                try:
                    # this is where, I am creating my joined cursor, on
which I only invoke, get(0) operation.
                    # self.db is primary database handle
                    joinedCursor = self.db.join(curs)
                    if not joinedCursor:
                        raise NextDigital.DBEOFException()
                    return (curs, joinedCursor)
                except Exception, e:
                    raise NextDigital.DBEOFException()
            else:
                cur = self.db.cursor()
                cur.set_range(pattern)
                return ([], cur)
        except Exception, e:
            print "Exception in search, case last: ", e
            #traceback.print_exc(file=sys.stdout)
            raise NextDigital.DBEOFException()


Ideally, pget shall set the pointer to some found record on secondary
cursor. But in my particular query, no records are found, that's where I
need to handle this error before calling join().

But, if we are getting stuck to the same vicious circle of finding
non-empty cursor, how could I determine, whether to join() or not
join()? As, join() is getting deadlock or core dump if we try to join
empty cursors.

Please suggest further.

Regards,

Surya

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