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rbql

0.9.0 • Public • Published

RBQL is both a library and a command line tool which provides SQL-like language with JavaScript expressions

Table of Contents

  1. RBQL as browser library
  2. RBQL as Node library
  3. RBQL as command line tool
  4. RBQL language description

Using RBQL as browser library

Installation:

In order to make RBQL work in browser as a library for your App you need just one single file: web_rbql.js To get it you can either use npm:

$ npm install rbql

Or just copy it directly from rbql.org:

$ wget https://rbql.org/web_rbql.js

Now you can just source web_rbql.js and it will work:

<script src="web_rbql.js"></script>

API description

The following two functions are avilable in the browser version:

  1. rbql.table_run(...)
  2. rbql.generic_run(...)

rbql.table_run(...)

Run user query against input array of records and put the result set in the output array:

function table_run(user_query, input_table, output_table, success_handler, error_handler, join_table=null)

Parameters:

  • user_query: string
    query that user of your app manually enters in some kind of input field.
  • input_table: array
    an array with input records
  • output_table: array
    an array where to output records would be pushed
  • success_handler: function(warnings) a callback which gets called on query success. warnings is an array of warning messages, which can be empty
  • error_handler: function(error_type, error_msg)
    a callback which gets called on query failure. error_type and error_msg are strings.
  • join_table: array
    an array with join table records so that user can use join table B in input queries

rbql.generic_run(...)

Allows to run queries against any kind of structured data.
You will have to implement special wrapper classes for your custom data structures and pass them to the rbql.generic_run(...) function.

function generic_run(user_query, input_iterator, output_writer, success_handler, error_handler, join_tables_registry=null)  

Parameters:

  • user_query: string
    query that user of your app manually enters in some kind of input field.
  • input_iterator: RBQLInputIterator
    special object which iterates over input records. E.g. over a remote table
  • output_writer: RBQLOutputWriter
    special object which stores output records somewhere. E.g. to an array
  • success_handler: function(warnings) a callback which gets called on query success. warnings is an array of warning messages, which can be empty
  • error_handler: function(error_type, error_msg) a callback which gets called on query failure. error_type and error_msg are strings.
  • join_tables_registry: RBQLJoinTablesRegistry
    special object which provides RBQLInputIterator iterators for join tables (e.g. table "B") which user can refer to in queries.

Examples of RBQLInputIterator, RBQLOutputWriter and RBQLJoinTablesRegistry implementations can be found in RBQL source code

Usage:

"Hello world" web test in RBQL

Very simple test to make sure that RBQL library works:

<!DOCTYPE html>
<html><head>

<script src="web_rbql.js"></script>
<script>
    let output_table = [];
    let error_handler = function(error_type, error_msg) {
        console.log('Error: ' + error_type + ': ' + error_msg);
    }
    let success_handler = function(warnings) {
        console.log('warnings: ' + JSON.stringify(warnings));
        console.log('output table: ' + JSON.stringify(output_table));
    }
    rbql.table_run('select a2 + " test", a1 limit 2', [[1, 'foo'], [2, 'bar'], [3, 'hello']], output_table, success_handler, error_handler);
</script>

<title>RBQL Generic Test</title>
</head>
<body><div><span>Open browser console</span></div></body>
</html>

Save the code above as rbql_test.html; put web_rbql.js in the same folder; open rbql_test.html in your browser and make sure that console output contains the expected result.

"JSFiddle" demo test

A little more advanced, but still very simple demo test with JSFiddle It uses the same web_rbql.js script file.

Using RBQL as Node library

Installation:

$ npm install rbql

API description

The following 3 functions are avilable in Node version:

  1. rbql.csv_run(...)
  2. rbql.table_run(...) - identical to browser version
  3. rbql.generic_run(...) - identical to browser version

rbql.csv_run(...)

Run user query against input_path CSV file and save it as output_path CSV file.

function rbql.csv_run(user_query, input_path, input_delim, input_policy, output_path, output_delim, output_policy, csv_encoding, success_handler, error_handler)

Parameters:

  • user_query: string
    query that user of your application manually enters in some kind of input field.
  • input_path: string
    path of the input csv table
  • input_delim: string
    field separator character in input table
  • input_policy: string
    allowed values: 'simple', 'quoted'
    along with input_delim defines CSV dialect of input table. "quoted" means that separator can be escaped inside double quoted fields
  • output_path: string
    path of the output csv table
  • output_delim: string
    same as input_delim but for output table
  • output_policy: string
    same as input_policy but for output table
  • csv_encoding: string
    allowed values: 'binary', 'utf-8'
    encoding of input, output and join tables (join table can be defined inside the user query)
  • success_handler: function(warnings) a callback which gets called on query success. warnings is an array of warning messages, which can be empty
  • error_handler: function(error_type, error_msg) a callback which gets called on query failure. error_type and error_msg are strings.

Usage:

Example of table_run() usage:

const rbql = require('rbql')

let input_table = [
    ['Roosevelt',1858,'USA'],
    ['Napoleon',1769,'France'],
    ['Dmitri Mendeleev',1834,'Russia'],
    ['Jane Austen',1775,'England'],
    ['Hayao Miyazaki',1941,'Japan'],
];
let user_query = 'SELECT a1, a2 % 1000 WHERE a3 != "USA" LIMIT 3';
let output_table = [];
let error_handler = function(error_type, error_msg) {
    console.log('Error: ' + error_type + ': ' + error_msg);
}
let success_handler = function(warnings) {
    console.log('warnings: ' + JSON.stringify(warnings));
    console.log('output table: ' + JSON.stringify(output_table));
}
rbql.table_run(user_query, input_table, output_table, success_handler, error_handler);

Example of csv_run() usage:

const rbql = require('rbql');

let user_query = 'SELECT a1, parseInt(a2) % 1000 WHERE a3 != "USA" LIMIT 5';
let error_handler = function(error_type, error_msg) {
    console.log('Error: ' + error_type + ': ' + error_msg);
}
let success_handler = function(warnings) {
    if (warnings.length)
        console.log('warnings: ' + JSON.stringify(warnings));
    console.log('output table: output.csv');
}
rbql.csv_run(user_query, 'input.csv', ',', 'quoted', 'output.csv', ',', 'quoted', 'utf-8', success_handler, error_handler);

You can also check rbql-js cli app code as a usage example: rbql-js cli source code

Using RBQL as command line tool

Installation:

To use RBQL as CLI app you need to install it in global (-g) mode:

$ npm install -g rbql

Usage (non-interactive mode):

$ rbql-js --query "select a1, a2 order by a1" < input.tsv

Usage (interactive mode):

In interactive mode rbql-js will show input table preview so it is easier to type SQL-like query.

$ rbql-js --input input.csv --output result.csv

Language description

Main Features

  • Use JavaScript expressions inside SELECT, UPDATE, WHERE and ORDER BY statements
  • Result set of any query immediately becomes a first-class table on it's own
  • Supports input tables with inconsistent number of fields per record
  • Output records appear in the same order as in input unless ORDER BY is provided
  • Each record has a unique NR (line number) identifier
  • Supports all main SQL keywords
  • Supports aggregate functions and GROUP BY queries
  • Provides some new useful query modes which traditional SQL engines do not have
  • Supports both TOP and LIMIT keywords
  • Supports user-defined functions (UDF)
  • Works out of the box, no external dependencies

Limitations:

  • RBQL doesn't support nested queries, but they can be emulated with consecutive queries
  • Number of tables in all JOIN queries is always 2 (input table and join table), use consecutive queries to join 3 or more tables

Supported SQL Keywords (Keywords are case insensitive)

  • SELECT
  • UPDATE
  • WHERE
  • ORDER BY ... [ DESC | ASC ]
  • [ LEFT | INNER ] JOIN
  • DISTINCT
  • GROUP BY
  • TOP N
  • LIMIT N

All keywords have the same meaning as in SQL queries. You can check them online

Special variables

Variable Name Variable Type Variable Description
a1, a2,..., a{N} string Value of i-th column
b1, b2,..., b{N} string Value of i-th column in join table B
NR integer Line number (1-based)
NF integer Number of fields in line

UPDATE statement

UPDATE query produces a new table where original values are replaced according to the UPDATE expression, so it can also be considered a special type of SELECT query. This prevents accidental data loss from poorly written queries.
UPDATE SET is synonym to UPDATE, because in RBQL there is no need to specify the source table.

Aggregate functions and queries

RBQL supports the following aggregate functions, which can also be used with GROUP BY keyword:
COUNT(), ARRAY_AGG(), MIN(), MAX(), SUM(), AVG(), VARIANCE(), MEDIAN()

Limitations

Aggregate functions inside Python (or JS) expressions are not supported. Although you can use expressions inside aggregate functions. E.g. MAX(parseFloat(a1) / 1000) - valid; MAX(a1) / 1000 - invalid

JOIN statements

Join table B can be referenced either by it's file path or by it's name - an arbitary string which user should provide before executing the JOIN query.
RBQL supports STRICT LEFT JOIN which is like LEFT JOIN, but generates an error if any key in left table "A" doesn't have exactly one matching key in the right table "B".

Limitations

  • JOIN statements must have the following form: <JOIN_KEYWORD> (/path/to/table.tsv | table_name ) ON ai == bj

SELECT EXCEPT statement

SELECT EXCEPT can be used to select everything except specific columns. E.g. to select everything but columns 2 and 4, run: SELECT * EXCEPT a2, a4
Traditional SQL engines do not support this query mode.

SELECT DISTINCT COUNT statement

RBQL supports DISTINCT COUNT keyword which is like DISTINCT, but adds a new column to the "distinct" result set: number of occurrences of the entry, similar to uniq -c unix command.
SELECT DISTINCT COUNT a1 is equivalent to SELECT a1, COUNT(a1) GROUP BY a1

UNNEST() operator

UNNEST(list) takes a list/array as an argument and repeats the output record multiple times - one time for each value from the list argument.
Example: SELECT a1, UNNEST(a2.split(';'))

User Defined Functions (UDF)

RBQL supports User Defined Functions
You can define custom functions and/or import libraries in the special file:

  • ~/.rbql_init_source.js - for JavaScript

Examples of RBQL queries

  • select top 100 a1, a2 * 10, a4.length where a1 == "Buy" order by parseInt(a2)
  • select * order by Math.random() - random sort, this is an equivalent of bash command sort -R
  • select top 20 a1.length / 10, a2 where ["car", "plane", "boat"].indexOf(a2) > -1
  • select a1.length / 10, a2 where ["car", "plane", "boat"].indexOf(a2) > -1 limit 20
  • update set a3 = 'US' where a3.indexOf('of America') != -1
  • select * where NR <= 10 - this is an equivalent of bash command "head -n 10", NR is 1-based')
  • select a1, a4 - this is an equivalent of bash command "cut -f 1,4"
  • select * order by parseInt(a2) desc - this is an equivalent of bash command "sort -k2,2 -r -n"
  • select NR, * - enumerate lines, NR is 1-based
  • select a1, b1, b2 inner join ./countries.txt on a2 == b1 order by a1, a3 - an example of join query
  • select distinct count a1.length where a2 != 'US'
  • select MAX(a1), MIN(a1) where a2 != 'US' group by a2, a3

References

install

npm i rbql

Downloadsweekly downloads

8

version

0.9.0

license

MIT

homepage

rbql.org

repository

Gitgithub

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