传动系统客户端
driveline的Python项目详细描述
驱动程序python sdk
Python SDK的核心是类DrivelineClient
importasynciofromdrivelineimportDrivelineClient,run_asyncasyncdefmain():asyncwithDrivelineClient('ws://127.0.0.1:8080')asclient:# list all streamsasyncforstream_nameinawaitclient.list_streams('*'):print('found stream:',stream_name)# list all keys is the document storeasyncforkey_nameinawaitclient.list_keys('*'):print('found document with key',key_name)# store a document in the document storeawaitclient.store('key/1',dict(title='Welcome',body='Hello, world!'))# load a key from the document storefuture_record=awaitclient.load('key/1')record=awaitfuture_recordprint('document associated with key/1 is:',record.record,'id:',record.record_id)# remove all records in the document store with keys matching 'key/...'awaitclient.removeMatches('key/*')# run a live query against a stream. # We want all records that have an odd indexdefquery_handler(res):print('query returned record:',res.record,'id:',res.record_id)query=awaitclient.continuous_query('SELECT * FROM STREAM my_stream where index % 1 == 1',query_handler)# stop the queryawaitasyncio.sleep(10)awaitclient.cancel(query)# quitawaitclient.close()if__name__=='__main__':run_async(main())
DQL动力传动系统查询语言
查询语法
基本语法
SELECT<selector>FROMSTREAM<stream>[WHERE<expression>]SELECT*FROMSTREAMstream_1SELECT*FROMSTREAMstream_1WHEREkey=valueSELECTtimeASt,(2+3)ASfiveFROMSTREAMstream_1WHEREageBETWEEN21AND25ORnameLIKE'Joe%'
DQL支持标准的查询语法，不包括连接和
聚合。这意味着DQL可以用于所有形式的数据过滤
以及在实时流上对数据进行分区
KV查询
SELECT<selector>FROM<string-key-name-expression>[WHERE<expression>]SELECT*FROM'users/*'WHEREcolor='red'
多键查询是一个DQL扩展，允许您订阅多个
事件流，在新流形成时自动订阅它们，
基于流名称表达式。流名称表达式使用文件系统/pythongGlob，
使用?、*和**作为通配符匹配字符。
ecmascript对象表示法（javascript扩展）
SELECT{time,name:user.name,phone_number:user.phone.mobile.number,original:{...*}}FROMstream
以表格形式输入：
{time:123,user:{name:'joe',phone:{mobile:{number:'1-800-123-4567'}}}}
结果：
{time:123,name:'joe',phone_number:'1-800-123-4567',original:{time:123,user:phone:{...}}}
运算符
下表按以下顺序汇总了所有语言运算符 优先级
| Name | Description | Example | Additional details |
|---|---|---|---|
| ^{ | extended logical OR | ^{ | ^{ |
| ^{ | logical AND | ^{ | ^{ |
| ^{ | logical NOT | ^{ | ^{ |
| ^{ | Null check | ^{ | ^{ |
| ^{ | Set lookup | ^{ | All values in paranthesis must be constants |
| ^{ | Compare range | ^{ | ^{ |
| ^{ | Compare | ^{ | |
| ^{ | Pattern match | ^{ | ^{ |
| ^{ | Unary plus/minus | ^{ | |
| ^{ | Addition | ^{ | |
| ^{ | Multiplicative | ^{ | |
| ^{ | Paranthesis | ^{ | |
| ^{ | Constant | ^{ | |
| ^{ | Numeric constant | ||
| ^{ | String constant | ^{ | |
| ^{ | Identifier | ^{ | |
| ^{ | Identifier | ^{ | (backticks) Allows using identifier names that are otherwise invalid, e.g., contain invalid characters or symbols |
内置函数
| Name | Description | Example |
|---|---|---|
| ABS | Absolute value ^{ | ^{ |
| CEIL | Rounded up value ^{ | ^{ |
| FLOOR | Rounded down value ^{ | ^{ |
| EXP | Natural exponent ^{ | ^{ |
| LN | Natural logarithm ^{ | ^{ |
| SQRT | Square root ^{ | ^{ |
| HASH | Hash function ^{ | ^{ |
| CHAR_LENGTH | Length of string ^{ | ^{ |
| POSITION | Index of substring in string ^{ | ^{ |
| LOCATE | Index of substring in string ^{ | ^{ |
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