mangogrep

A command-line utility that "greps" stdin, applying a CouchDB-style Mango "selector" to filter the data, with matching items being passed to stdout.

If we have a a "jsonl" file (one JSON object per line in a text file) (or one array of objects per line):

{"_id":"735030","_rev":"1-a6a5871f06709450a7e3d14fccf4484c","name":"Náousa","latitude":40.62944,"longitude":22.06806,"country":"GR","population":19887,"timezone":"Europe/Athens","_revisions":{"start":1,"ids":["a6a5871f06709450a7e3d14fccf4484c"]}}
{"_id":"735861","_rev":"1-73f30984f6891cdcc0dfdcfe6277233d","name":"Kavála","latitude":40.93959,"longitude":24.40687,"country":"GR","population":54027,"timezone":"Europe/Athens","_revisions":{"start":1,"ids":["73f30984f6891cdcc0dfdcfe6277233d"]}}
{"_id":"694864","_rev":"1-09af55b85cac9974b691abf0f621dec0","name":"Sambir","latitude":49.5183,"longitude":23.19752,"country":"UA","population":35197,"timezone":"Europe/Kiev","_revisions":{"start":1,"ids":["09af55b85cac9974b691abf0f621dec0"]}}

We can use mangogrep to extract a subset of the data:

# find documents that contain a 'country' field whose value is 'UA'
$ cat myfile.jsonl | mangogrep --selector '{"country":"UA"}'
{"_id":"694864","_rev":"1-09af55b85cac9974b691abf0f621dec0","name":"Sambir","latitude":49.5183,"longitude":23.19752,"country":"UA","population":35197,"timezone":"Europe/Kiev","_revisions":{"start":1,"ids":["09af55b85cac9974b691abf0f621dec0"]}}

Installation

Requires Node.js & npm

npm install -g mangogrep

Usage

• --selector/-s - the Mango Selector to apply to the incoming data e.g. {"latitude":{"$gt":54.5}}
• --where/-w - the SQL 'where' clause to apply to the incoming data e.g. latitude > 54.5
• --debug/-d - output the selector to stderr
• --help - output help

If neither selector or where are supplied, then all incoming data makes it to the output, one object per line.

Example usage

JSONL files

JSONL files contain one JSON object per line of output. The couchsnap utiltity creates such files, so mangogrep is good for finding slices of data from a single backup snapshot:

# find a single document id from a single file
cat mydb-snapshot-2022-11-09T16:04:51.041Z.jsonl | mangogrep --where "_id='0021MQOXCM3HNHAF'"

or all of your backup snapshots:

# see the history of single document id from multiple snapshot files
cat mydb-snapshot* | mangogrep --where "_id='0021MQOXCM3HNHAF'"

The query can be complex, with lots of ANDs and ORs:

# find documents with a combination of SQL-like AND/OR clauses
cat mydb-snapshot* | mangogrep --where "(active=true OR email_verified=true) AND email='[e-mail]'"

Or you can use Mango selectors, which unlocks per-field regular expressions:

# use a regular expression on the email field to find all documents with hotmail email fields
cat mydb-snapshot* | mangogrep --selector '{"email":{"$regex":"@hotmail"}}'

Couchbackup files

@cloudant/couchbackup stores its backup data in text files containing an array of documents per line, but mangogrep will handle this as if they were JSONL files.

# backup your data
couchbackup --db users > users.txt

# query the backup data set, piping the output to a file
cat users.txt | mangogrep --where "joined>'2022-01-01'" > 2022_users.jsonl

Aggregation

You may combine mangogrep with other command-line tools for aggregating answers:

# count users who joined this year and are active
cat users.txt | mangogrep --where "joined>'2022-01-01' AND active=true" | wc -l