Driveline Javascript SDK

At the core of the Javascript SDK is the class DrivelineClient.

DrivelineClient.connect('ws://127.0.0.1:8080', {onConnected:main});

const main = (client) => {

  // list all streams
  // name is null when all streams have been listed
  client.listStreams('*', (name)=> console.log(name));
  
  // list all keys in the Key-Value store
  // name is null when all keys have been listed
  client.listKeys('*', (name) => console.log(name));

  // load a key from the key-value store
  client.load('kv[1]').then(({recordId, record, error}) => {
    if (error) {
        alert('something bad happened: ' + error);
        return;
    }
    // go on with recordId and record
    console.log('loaded record with id:', recordId, 'value:', record);
  });
  
  // remove all records in the key-value store which keys matching 'kv[...]'
  // this will watch kv[1], kv[12321312], kv[say whaaaat?]
  client.removeMatches('kv[*]');
  
  // store an object in the key-value store at key 'kv[2]'
  client.store('kv[2]', {message:'hello, world!'});

  // run a live query against a stream.
  // in this case we want every records
  client.continuousQuery('SELECT * FROM STREAM stream1', ({ recordId, record, error}) => {
      // process ... 
  });
  
};

DQL Driveline Query Language

Query syntax

Basic syntax

SELECT <selector> FROM STREAM <stream> [WHERE <expression>]
SELECT * FROM STREAM stream_1
SELECT * FROM STREAM stream_1 WHERE key=value
SELECT time AS t,(2+3) AS five FROM STREAM stream_1 WHERE age BETWEEN 21 AND 25 OR name LIKE 'Joe%'

DQL supports standard SQL query syntax, excluding Joins and Aggregates. This means DQL can be used for all forms of data filtering and partitioning of data over live streams.

KV query

SELECT <selector> FROM <string-key-name-expression> [WHERE <expression>]
SELECT * FROM 'users/*' WHERE color='red'

Multi key query is a DQL extension that lets you subscribe to multiple event streams, automatically subscribing to new streams as they form, based on the stream name expression. Stream name expression use file-system/Pythong Glob, with ?, * and ** serving as the wildcard match characters.

ECMAScript Object Notation (JavaScript extensions)

SELECT {time,name:user.name,phone_number:user.phone.mobile.number,original:{...*}} FROM stream

With inputs of the form:

{time:123, user: {name:'joe', phone: {mobile: {number:'1-800-123-4567'}}}}

Results in:

{time:123,name:'joe',phone_number:'1-800-123-4567',original:{time:123,user:phone:{...}}}

Operators

The following table summarizes all language operators in order of precedence

| Name | Description | Example | Additional details | |:------------------------------------------|:--------------------|:------------------------------------------------------|:------------------------------------------------------------------------------------------------------------------| | OR | extended logical OR | SELECT * FROM STREAM stream WHERE a OR b | if (a) return a; else return b; | | AND | logical AND | SELECT * FROM STREAM stream WHERE a AND b | if (a && b) return true; else return false; | | NOT | logical NOT | SELECT * FROM STREAM stream WHERE NOT a | if (a) return false; else return true; | | IS [NOT] NULL | Null check | SELECT * FROM STREAM stream WHERE a IS NOT NULL | if (null===a) return true; return false; | | IN | Set lookup | SELECT * FROM STREAM stream WHERE a IN (1,2,3) | All values in paranthesis must be constants | | BETWEEN | Compare range | SELECT * FROM STREAM stream WHERE a BETWEEN b AND c | if (b<c) return (a>=b && a<=c); else return (a>=c && a<=b); | | = >= <= != > < !< !> <> | Compare | SELECT * FROM STREAM STREAM WHERE a <> b | | | LIKE | Pattern match | SELECT * FROM STREAM stream WHERE a like '%b%' | _ stands for single, % stands for multi-char match | | + - | Unary plus/minus | SELECT * FROM STREAM stream WHERE -5 < +5 | | | + - | Addition | SELECT * FROM STREAM stream WHERE 1+2=3 | | | * / % | Multiplicative | SELECT * FROM STREAM stream WHERE 3%2=1 | | | ( exp ) | Paranthesis | SELECT * FROM STREAM stream WHERE (1+2)*3=9 | | | true false null | Constant | SELECT * FROM STREAM stream WHERE true != false | | | -123.45e-1 | Numeric constant | | | | 'hello' | String constant | | SELECT * FROM stream WHERE name='joe' | | name | Identifier | SELECT name FROM STREAM stream | | | `user name` | Identifier | SELECT `user name` FROM STREAM stream | (backticks) Allows using identifier names that are otherwise invalid, e.g., contain invalid characters or symbols |

Built-in functions

| Name | Description | Example | |:------------|:----------------------------------------------------|:--------------------------------------------------------------------| | ABS | Absolute value float=>float | SELECT ABS(-5) AS num FROM stream {num:5} | | CEIL | Rounded up value float=>float | SELECT CEIL(4.5) AS num FROM stream {num:5} | | FLOOR | Rounded down value float=>float | SELECT FLOOR(4.5) AS num FROM stream {num:4} | | EXP | Natural exponent float=>float | SELECT EXP(1) AS num FROM stream {num:2.718281828459045} | | LN | Natural logarithm float=>float | SELECT LN(2) AS num FROM stream {num:0.6931471805599453} | | SQRT | Square root float=>float | SELECT SQRT(9) AS num FROM stream {num:3} | | HASH | Hash function any=>uint64 | SELECT HASH('abc') AS num FROM stream {num:4952883123889572249} | | CHAR_LENGTH | Length of string string->int32 | SELECT CHAR_LENGTH('abc') AS num FROM stream {num:3} | | POSITION | Index of substring in string string,string->int32 | SELECT POSITION('bc' IN 'abc') AS num FROM stream {num:2} | | LOCATE | Index of substring in string string,string->int32 | SELECT LOCATE('bc', 'abc') AS num FROM stream {num:2} |