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Driveline client

Project description

Driveline Python SDK

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

import asyncio

from driveline import DrivelineClient, run_async

async def main():
    async with DrivelineClient('ws://127.0.0.1:8080') as client:

        # list all streams
        async for stream_name in await client.list_streams('*'):
            print('found stream:', stream_name)

        # list all keys is the document store
        async for key_name in await client.list_keys('*'):
            print('found document with key', key_name)


        # store a document in the document store
        await client.store('key/1', dict(title='Welcome', body='Hello, world!'))

        # load a key from the document store
        future_record = await client.load('key/1')
        record = await future_record
        print('document associated with key/1 is:', record.record, 'id:', record.record_id)

        # remove all records in the document store with keys matching 'key/...'
        await client.removeMatches('key/*')

        # run a live query against a stream. 
        # We want all records that have an odd index
        def query_handler(res):
            print('query returned record:', res.record, 'id:', res.record_id)
        query = await client.continuous_query('SELECT * FROM STREAM my_stream where index % 1 == 1', query_handler)


        # stop the query
        await asyncio.sleep(10)
        await client.cancel(query)

        # quit
        await client.close()

if __name__ == '__main__':
    run_async(main())

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}

Project details


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