On Wed, 02 May 2012 09:13:35 -0500, Bill House

<wch-tech@house-grp.net> declaimed the

following in gmane.comp.python.dabo.user:

> Given a dbase table called

>

> files

>

> with a structure of

>

> md5sum char 30

> path char 450

> file_name char 220

>

> and indexed (or sorted) in the order of

>

> md5sum + path + file_name

>

> run the following script

>

> <CODE>

> ********************** mark_del.prg **********************

> *mark all records with identical md5sums as deleted

> *except for last one

You apparently have no primary key or other means of identifying

order... Otherwise I'd suggest ordering IN REVERSE so the first

appearance of an md5sum value is the one to keep, and any subsequent

identical records are to be deleted. Oh well... Hypothetical is that the

one to keep is the one whose path/name sorts last...

#pseudo code including raw database operations

csr = con.cursor() #get a cursor for the database connection

csr.execute("""select md5sum, path, file_name

from files

order by md5sum desc,

path desc,

file_name desc""")

lastMD5 = None

for rec in csr.fetchall(): #I'm not sure if you can issue a new

#command on the cursor before

#reading all the data

if rec[0] == lastMD5:

#substitute the appropriate placeholder;

#MySQLdb uses %s, SQLite3 uses ?

csr.execute("""delete from files where

md5sum = %s and

path = %s and

file_name = %s""",

(rec[0], rec[1], rec[2]))

else:

lastMD5 = rec[0]

csr.close()

con.commit() #all the deletes now happen

--

Wulfraed Dennis Lee Bieber AF6VN

wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/

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