spyql 0.9.0

SPyQL: SQL with Python in the middle

SQL with Python in the middle

About

SPyQL is a query language that combines:

• the simplicity and structure of SQL;

• with the power and readability of Python.

SELECT
    date.fromtimestamp(.purchase_ts) AS purchase_date,
    .price * .quantity AS total
FROM json
WHERE .department.upper() == 'IT'
ORDER BY 2 DESC
TO csv

SQL provides the structure of the query, while Python is used to define expressions, bringing along a vast ecosystem of packages.

SPyQL is fast and memory efficient. Take a look at the benchmarks with GB-size JSON data.

SPyQL CLI

SPyQL offers a command-line interface that allows running SPyQL queries on top of text data (e.g. CSV, JSON). Data can come from files but also from data streams, such as as Kafka, or from databases such as PostgreSQL. Basically, data can come from any command that outputs text :-). More, data can be generated by a Python expression! And since SPyQL also writes to different formats, it allows to easily convert between data formats.

Take a look at the Command line examples to see how to query parquet, process API calls, transverse directories of zipped JSONs, convert CSV to JSON, and import JSON/CSV data into SQL databases, among many other things.

See also:

• Tutorial (v0.8)

• Demo video (v0.4)

SPyQL Module

SPyQL is also available as a Python module. In addition to the CLI features, you can also:

• query variables (e.g. lists of dicts);

• get results into in-memory data structures.

Principles

We aim for SPyQL to be:

• Simple: simple to use with a straightforward implementation;

• Familiar: you should feel at home if you are acquainted with SQL and Python;

• Light: small memory footprint that allows you to process large data that fit into your machine;

• Useful: it should make your life easier, filling a gap in the eco-system.

Distinctive features of SPyQL

• Row order guarantee

• Natural window for aggregations

• No distinction between aggregate and window functions

• IMPORT clause

• Natural support for lists, sets, dictionaries, objects, etc

• 1-liner by design

• Multiple data formats supported

Testimonials

“I’m very impressed - this is some very neat pragmatic software design.”

Simon Willison, Creator of Datasette, co-creator of Django

“I love this tool! I use it every day”…

Alin Panaitiu, Creator of Lunar

“Brilliant tool, thanks a lot for creating it and for the example here!”

Greg Sadetsky, Co-founder and CTO at Decibel Ads

Documentation

The official documentation of SPyQL can be found at: https://spyql.readthedocs.io/.

Installation

The easiest way to install SPyQL is from pip:

pip install spyql

Hello world

To test your installation run in the terminal:

spyql "SELECT 'Hello world' as Message TO pretty"

Output:

Message
-----------
Hello world

You can try replacing the output format by JSON or CSV, and adding more columns. e.g. run in the terminal:

spyql "SELECT 'Hello world' as message, 1+2 as three TO json"

Output:

{"message": "Hello world", "three": 3}

Example queries

You can run the following example queries in the terminal: spyql "the_query" < a_data_file

Example data files are not provided on most cases.

Query a CSV (and print a pretty table)

SELECT a_col_name, 'positive' if int(col2) >= 0 else 'negative' AS sign
FROM csv
TO pretty

Convert CSV to a flat JSON

SELECT * FROM csv TO json

Convert from CSV to a hierarchical JSON

SELECT {'client': {'id': col1, 'name': col2}, 'price': 120.40} AS json
FROM csv TO json

or

SELECT {'id': col1, 'name': col2} AS client, 120.40 AS price
FROM csv TO json

JSON to CSV, filtering out NULLs

SELECT .client.id AS id, .client.name AS name, .price
FROM json
WHERE .client.name is not NULL
TO csv

Explode JSON to CSV

SELECT .invoice_num AS id, .items.name AS name, .items.price AS price
FROM json
EXPLODE .items
TO csv

Sample input:

{"invoice_num" : 1028, "items": [{"name": "tomatoes", "price": 1.5}, {"name": "bananas", "price": 2.0}]}
{"invoice_num" : 1029, "items": [{"name": "peaches", "price": 3.12}]}

Output:

id, name, price
1028, tomatoes, 1.5
1028, bananas, 2.0
1029, peaches, 3.12

Python iterator/list/comprehension to JSON

SELECT 10 * cos(col1 * ((pi * 4) / 90))
FROM range(80)
TO json

or

SELECT col1
FROM [10 * cos(i * ((pi * 4) / 90)) for i in range(80)]
TO json

Importing python modules

Here we import hashlib to calculate a md5 hash for each input line. Before running this example you need to install the hashlib package (pip install hashlib).

IMPORT hashlib as hl
SELECT hl.md5(col1.encode('utf-8')).hexdigest()
FROM text

Getting the top 5 records

SELECT int(score) AS score, player_name
FROM csv
ORDER BY 1 DESC NULLS LAST, score_date
LIMIT 5

Aggregations

Totals by player, alphabetically ordered.

SELECT .player_name, sum_agg(.score) AS total_score
FROM json
GROUP BY 1
ORDER BY 1

Partial aggregations

Calculating the cumulative sum of a variable using the PARTIALS modifier. Also demoing the lag aggregator.

SELECT PARTIALS
    .new_entries,
    sum_agg(.new_entries) AS cum_new_entries,
    lag(.new_entries) AS prev_entries
FROM json
TO json

Sample input:

{"new_entries" : 10}
{"new_entries" : 5}
{"new_entries" : 25}
{"new_entries" : null}
{}
{"new_entries" : 100}

Output:

{"new_entries" : 10,   "cum_new_entries" : 10,  "prev_entries": null}
{"new_entries" : 5,    "cum_new_entries" : 15,  "prev_entries": 10}
{"new_entries" : 25,   "cum_new_entries" : 40,  "prev_entries": 5}
{"new_entries" : null, "cum_new_entries" : 40,  "prev_entries": 25}
{"new_entries" : null, "cum_new_entries" : 40,  "prev_entries": null}
{"new_entries" : 100,  "cum_new_entries" : 140, "prev_entries": null}

If PARTIALS was omitted the result would be equivalent to the last output row.

Distinct rows

SELECT DISTINCT *
FROM csv

Command line examples

To run the following examples, type Ctrl-x Ctrl-e on you terminal. This will open your default editor (emacs/vim). Paste the code of one of the examples, save and exit.

Queries on Parquet with directories

Here, find transverses a directory and executes parquet-tools for each parquet file, dumping each file to json format. jq -c makes sure that the output has 1 json per line before handing over to spyql. This is far from being an efficient way to query parquet files, but it might be a handy option if you need to do a quick inspection.

find /the/directory -name "*.parquet" -exec parquet-tools cat --json {} \; |
jq -c |
spyql "
    SELECT .a_field, .a_num_field * 2 + 1
    FROM json
"

Querying multiple json.gz files

gzcat *.json.gz |
jq -c |
spyql "
    SELECT .a_field, .a_num_field * 2 + 1
    FROM json
"

Querying YAML / XML / TOML files

yq converts yaml, xml and toml files to json, allowing to easily query any of these with spyql.

cat file.yaml | yq -c | spyql "SELECT .a_field FROM json"

cat file.xml | xq -c | spyql "SELECT .a_field FROM json"

cat file.toml | tomlq -c | spyql "SELECT .a_field FROM json"

Kafka to PostegreSQL pipeline

Read data from a kafka topic and write to postgres table name customer.

kafkacat -b the.broker.com -t the.topic |
spyql -Otable=customer -Ochunk_size=1 --unbuffered "
    SELECT
        .customer.id AS id,
        .customer.name AS name
    FROM json
    TO sql
" |
psql -U an_user_name -h a.host.com a_database_name

Monitoring statistics in Kafka

Read data from a kafka topic, continuously calculating statistics.

kafkacat -b the.broker.com -t the.topic |
spyql --unbuffered "
    SELECT PARTIALS
        count_agg(*) AS running_count,
        sum_agg(value) AS running_sum,
        min_agg(value) AS min_so_far,
        value AS current_value
    FROM json
    TO csv
"

Sub-queries (piping)

A special file format (spy) is used to efficiently pipe data between queries.

cat a_file.json |
spyql "
    SELECT ' '.join([.first_name, .middle_name, .last_name]) AS full_name
    FROM json
    TO spy" |
spyql "SELECT full_name, full_name.upper() FROM spy"

(Equi) Joins

It is possible to make simple (LEFT) JOIN operations based on dictionary lookups.

Given numbers.json:

{
   "1": "One",
   "2": "Two",
   "3": "Three"
}

Query:

spyql -Jnums=numbers.json "
        SELECT nums[col1] as res
        FROM [3,4,1,1]
        TO json"

Output:

{"res": "Three"}
{"res": null}
{"res": "One"}
{"res": "One"}

If you want a INNER JOIN instead of a LEFT JOIN, you can add a criteria to the where clause, e.g.:

SELECT nums[col1] as res
FROM [3,4,1,1]
WHERE col1 in nums
TO json

Output:

{"res": "Three"}
{"res": "One"}
{"res": "One"}

Queries over APIs

curl https://reqres.in/api/users?page=2 |
spyql "
    SELECT
        .data.email AS email,
        'Dear {}, thank you for being a great customer!'.format(.data.first_name) AS msg
    FROM json
    EXPLODE .data
    TO json
"

Plotting to the terminal

spyql "
    SELECT col1
    FROM [10 * cos(i * ((pi * 4) / 90)) for i in range(80)]
    TO plot
"

Plotting with matplotcli

spyql "
   SELECT col1 AS y
   FROM [10 * cos(i * ((pi * 4) / 90)) for i in range(80)]
   TO json
" | plt "plot(y)"

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