redundant_indexes.py

#!/usr/bin/env python

"""
This is a simple script to print out potentially redundant indexes in a mongdb instance.
For example, if an index is defined on {field1:1,field2:1} and there is another index
with just fields {field1:1}, the latter index is not needed since the first index already
indexes the necessary fields.
"""
from pymongo import Connection
from pymongo import ReadPreference
from optparse import OptionParser


def get_cli_options():
    parser = OptionParser(usage="usage: python %prog [options]",
                          description="""This script prints some basic collection stats about the size of the collections and their indexes.""")

    parser.add_option("-H", "--host",
                      dest="host",
                      default="localhost",
                      metavar="HOST",
                      help="MongoDB host")
    parser.add_option("-p", "--port",
                      dest="port",
                      default=27017,
                      metavar="PORT",
                      help="MongoDB port")
    parser.add_option("-d", "--database",
                      dest="database",
                      default="",
                      metavar="DATABASE",
                      help="Target database to generate statistics. All if omitted.")
    parser.add_option("-u", "--user",
                      dest="user",
                      default="",
                      metavar="USER",
                      help="Admin username if authentication is enabled")
    parser.add_option("--password",
                      dest="password",
                      default="",
                      metavar="PASSWORD",
                      help="Admin password if authentication is enabled")

    (options, args) = parser.parse_args()

    return options

def get_connection(host, port, database, username, password):
    userPass = ""
    if username and password:
        userPass = username + ":" + password + "@"

    mongoURI = "mongodb://" + userPass + host + ":" + str(port) + '/' + database
    return Connection(host=mongoURI, read_preference=ReadPreference.SECONDARY)

def main(options):
    connection = get_connection(options.host, options.port, options.database, options.user, options.password)

    def compute_signature(index):
        signature = index["ns"]
        for key in index["key"]:
            try:
                signature += "%s_%s" % (key, int(index["key"][key]))
            except ValueError:
                signature += "%s_%s" % (key, index["key"][key])
        return signature

    def report_redundant_indexes(current_db):
        print "Checking DB: %s" % current_db.name
        indexes = current_db.system.indexes.find()
        index_map = {}
        for index in indexes:
            signature = compute_signature(index)
            index_map[signature] = index

        for signature in index_map.keys():
            for other_sig in index_map.keys():
                if signature == other_sig:
                    continue
                if other_sig.startswith(signature):
                    print "Index %s[%s] may be redundant with %s[%s]" % (
                        index_map[signature]["ns"],
                        index_map[signature]["name"],
                        index_map[other_sig]["ns"],
                        index_map[other_sig]["name"])

    databases= []
    if options.database:
        databases.append(options.database)
    else:
        databases = connection.database_names()

    for db in databases:
        report_redundant_indexes(connection[db])

if __name__ == "__main__":
    options = get_cli_options()
    main(options)