Hi,
I've been having problems using the "where" clause and I would appreciate
any suggestions.
The problem occurs when I try to use a "where" clause to access records that
are near the end of the file and when the file has been built from multiple
runs. The code below demonstrates the problem.
If the script below is started with the command line parameter of "good", it
generates a table of 40,000 records. Then if the script is run with the
command line parameter of "read", the record is found with both the
sequential and indexed searches.
If the script is started with the command line parameter of "bad", the table
is generated in separate passes. Each pass writes opens the file, writes
1000 records and closes the file. Then if the script is run with the
command line parameter of "read", the record is only found in the sequential
search.
A possibly related problem is that when the "bad" version of the file is
generated, ptdump crashes.
Thanks for any help you can provide.
David
#!/usr/bin/python
from tables import *
import sys
# Define a user record to characterize some kind of particles
class Particle(IsDescription):
name = StringCol(16, indexed = True) # 16-character String
def write (start, stop):
print "start, stop = %d, %d" % (start, stop)
if start == 0:
open_mode = "w"
else:
open_mode = "a"
# Open a file in "w"rite mode
h5file = openFile("test.h5", mode = open_mode, title = "Test file")
if start == 0:
# Create a new group under "/" (root)
group = h5file.createGroup("/", 'detector', 'Detector
information')
# Create one table on it
table = h5file.createTable(group, 'readout', Particle, "Readout
example")
else:
table = h5file.root.detector.readout
# Fill the table with 10 particles
particle = table.row
for i in xrange(start, stop):
particle['name'] = 'Particle: %6d' % (i)
# Insert a new particle record
particle.append()
# Close (and flush) the file
if start > 0:
table.reIndex()
h5file.close()
def where (particle_name):
h5file = openFile("test.h5", mode = "r", title = "Test file")
index = h5file.root.detector.readout
count = 0
for row in index.where (index.cols.name == particle_name):
count += 1
print row ["name"]
print "indexed search found %d matches" % count
def seq (particle_name):
h5file = openFile("test.h5", mode = "r", title = "Test file")
index = h5file.root.detector.readout
count = 0
for row in index:#.where (index.cols.name == particle_name):
if row ['name'] == particle_name:
count += 1
print row ["name"]
print "sequential search found %d matches" % count
if __name__ == "__main__":
if sys.argv [1] == "good" or sys.argv [1] == "bad":
if sys.argv [1] == "good":
start = 0
stop = 40000
end = 1
else:
if sys.argv [1] == "bad":
start = 0
stop = 1000
end = 40
for x in range (0, end):
write (start, stop)
start = stop
stop += 1000
else:
particle_name = "Particle: 36001" # works only with "good"
write
# particle_name = "Particle: 25001" # always works
where (particle_name)
seq (particle_name)
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