Hello,
It looks like copy_from does not stop reading after an error. When the input file is short, it is okay. But when the input file is very long, it is really boring to wait for the entire file to be read just to discover there is an error on the 10th row.
Given the same input file, it looks like psql \copy command behaves correctly and stops just after the incorrect row, without reading the entire file. I have checked that just by looking at the command execution time that seems proportional to the number of processed rows...
Here is a script to reproduce this bug (just create a database "test" and run the script):
I don't know what to do with this bug. Thanks for your help and advice.
Regards,
Nicolas Grilly
Here is the same script inline:
import traceback
import psycopg2
def main():
con = psycopg2.connect(database='test', user='postgres')
cur = con.cursor()
try:
cur.execute("create temp table test (id integer primary key, data text)")
rows = iter_rows()
copy_file = CopyFile(rows)
cur.copy_from(copy_file, 'test')
cur.execute("select count(*) from test")
print "{0} rows written to database".format(cur.fetchall()[0][0])
finally:
cur.close()
con.close()
def iter_rows():
random_data = 'x' * 100
for i in range(0, 500):
if i == 10:
i = 'Bad key'
print "Yield incorrect data row (copy_from should stop reading after that)"
else:
print "Yield correct data row"
yield '{0}\t{1}\n'.format(i, random_data)
class CopyFile(object):
def __init__(self, row_reader):
self.next_row = row_reader.next
self.buffer = ''
def read(self, limit=-1):
print "Read {0} bytes".format(limit)
try:
buffer = self.buffer
while limit < 0 or len(buffer) < limit:
try:
buffer += self.next_row()
except StopIteration:
break
if limit < 0:
self.buffer = ''
return buffer
else:
self.buffer = buffer[limit:]
return buffer[:limit]
except:
# Report unexpected errors because psycopg2 does not report them
traceback.print_exc()
raise
# Method readline is required by psycopg2 but actually never called
def readline(self, limit=-1):
raise NotImplementedError()
if __name__ == '__main__':
main()
