Saturday, August 19, 2017

Fast autocomplete using Python and Redis

Fast autocomplete using Python and Redis

General information

Problem

Imagine situation when you need provide autocomplete for some data list. In case when you using SQL probably you will do something like this:

select * from table_name where table_field like 'search%'
 
Probably you know, that when you database contains significant amount of data you will get essential decreasing of data processing.



Source code can be found at:
https://github.com/JFF-Bohdan/console_fast_autocomplete

Disclaimer

This repository contains dictionaries found on some FTPs and other repos. They can be found in data folder.

Solution

Base information

You can use Redis NoSQL to perform fast autocomplete. First of all you need load all data into Redis database and then give interface to perform sarch queries.

Loading data

First of all we will use ZADD command to load items into sorted set. We will specify same score 0.0 to each item, so them will sorted lexicographically in the set.

To implement case intensive search we will use some little trick. Before adding each item to the set we will convert it to lowercase and will add original item after : separator. So when we have want add word Wood to the set, actually we will add wood:Wood. In this case we will be able to perform case intensive search and also save original word.

We will use pipelines (part of redis Python library) to increase loading speed. They will help us to buffer ZADD commands and reduce the number of back-and-forth TCP packets between the client and server. They helps us to dramatically increase the loading performance.

Performing search

We will use ZRANGEBYLEX command and will load all strings which starts with query string. So it's will be actual implementation of autocomplete. BTW, superfast autocomplete: we can perform search for string alexa for 520679 items just in 30-35ms at my laptop.

Installation

Just clone this repository using git and then and install dependancies using:
pip install -r requirements.txt

Usage

Configuration file

You can find example configuration file in:
.\conf\default.conf
You need specify connection to redis, folder with data and temporary
[main]
temp_path=./tmp

[redis]
host=localhost
port=6379
password=
db=0

[data]
main_source=./data/
Where:
  • redis connection to redis;
  • data::main_source - folder with data;
  • main::temp_path - folder for .zip files unpacking

Initializing database

You can load all information from data files using:
string_search.py --config .\conf\default.conf --init-data
program will look for all files in this folder. If .zip file will be found, it will be uncompressed into temporary folder for further loading.
This operation can took long time, up to 1 minute on slow machines.

Performing search

To perform search for alexa query you should use:
string_search.py --config .\conf\default.conf --search alexa

Checking items count

You can check count of items in database by using:
string_search.py --config .\conf\default.conf --get-length

Enjoy!

2 comments:

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