IMServer:MongoDB: Difference between revisions
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[[Category:Connectome]] | |||
== MongoDB == | == MongoDB == | ||
| Line 8: | Line 11: | ||
== Creating indexes == | == Creating indexes == | ||
Following is a python script which loops through all the collections of a database and ensure index over field "name" | |||
<pre lang="python"> | <pre lang="python"> | ||
import pymongo | import pymongo | ||
| Line 40: | Line 43: | ||
=== How to find if a collection exists === | === How to find if a collection exists === | ||
Following is the sequence of commands to be typed in mongo command line client to find out whether a named collection exists. | |||
That can be done by querying system.namespaces collection in that database, which lists all the collections | |||
< | <pre lang="javascript"> | ||
show dbs | show dbs | ||
use clay1 | use clay1 | ||
db.system.namespaces.find({ "name" :"clay1.n5"}) | db.system.namespaces.find({ "name" :"clay1.n5"}) | ||
</ | </pre> | ||
"clay1" is the name of the database, and "n5" is the name of the collection to find | "clay1" is the name of the database, and "n5" is the name of the collection to find | ||
Latest revision as of 18:10, 19 January 2011
MongoDB
- 64 bit recommended due to 2gb data size barrier in 32bit
- 1.7.4 has some enhancements like 16mb limit per binary record
- Binary can be downloaded from
- On deployment server, needs a script to be installed in init.d to stop / restart / start mongodb
Creating indexes
Following is a python script which loops through all the collections of a database and ensure index over field "name"
import pymongo
# connect with the database
try:
conn = pymongo.Connection()
db = conn['clay1']
print 'Connection OK'
except:
print 'Cound not Connect ..'
# loop through all collections
cols = db.collection_names()
for col_name in cols:
# skip if starts with system
if col_name[0:6] <> 'system':
print 'Opening collection : ' + col_name
col = db[col_name]
print ' With %d records'%(col.count())
print ' ' + str(col.index_information())
print ' Creating index ...'
col.ensure_index("name")
print "\r Done ... "
Cookbook
How to find if a collection exists
Following is the sequence of commands to be typed in mongo command line client to find out whether a named collection exists. That can be done by querying system.namespaces collection in that database, which lists all the collections
show dbs
use clay1
db.system.namespaces.find({ "name" :"clay1.n5"})
"clay1" is the name of the database, and "n5" is the name of the collection to find
