DolphinDB is a high performance time series database. It is written in C++ and optimized for fast injection, storage, retrieval and analysis of time series data in fields such as quantitative finance, Internet of Things, real-time analytics, etc. DolphinDB runs extremely fast. It is also easy to use as the syntax of the programming language of DolphinDB is similar to SQL and Python.
Questions tagged [dolphindb]
764 questions
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Undefine all shared variables on the current node
I have defined multiple shared tables in the current node. Are there any ways or built-in functions to undefine them at one time?
FFF
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2 answers
Best way to declare and define global variables in DolphinDB
I’d like to define some global configuration parameters to share them across sessions. How do I declare and define global variables in DolphinDB?
FFF
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1 answer
Does DolphinDB have an equivalent method to Python join?
In Python, I can join all elements into a string separated by a string separator with method join().
>>> ','.join(["{}D".format(i) for i in range(1,6)])
'1D,2D,3D,4D,5D'
How can I implement the function equivalent to join in DolphinDB?
Polly
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DolphinDB: chunks distribution of a dfs table in a cluster
How to get the distribution of all the chunks of a dfs table in a cluster with DolphinDB? I've tried getChunksMeta but it only returned the chunk information.
YaN
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How to update all volume values at 09:31m for each stock in DolphinDB?
I’m using DolphinDB for historical data processing.
Can I update the field “volume” at 09:31m for each market stock with the summed values at 09:31m and 09:30m?
Polly
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1 answer
how to check if a stream table exists using DolphinDB?
How to know if a StreamTable or KeyedStreamTable exists? I tried using exists and existsTable but I am not sure what dbURL to enter.
Eva Gao
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1 answer
calculate the percentile rank of the maximum value duration (DolphinDB)
Suppose there are 4800 ticks per day for a stock. All the ticks are evenly spread over time. How can I calculate the time percentile rank of the maximum value within the time window in DolphinDB?
Eva Gao
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1 answer
How to update the first row records for each stock in a DolphinDB table?
I'd like to update the first price record for each stock without changing other records. The problem is I cannot find an efficient way to set the conditions concisely as a stock id column contains various stocks. Any suggestions on function use?
btw…
YaN
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1 answer
The specific role of worker in DolphinDB?
What does worker, secondaryWorker, web worker, infra worker, dynamic worker, and local executors stand for respectively in DolphinDB? Why the secondaryWorker and dynamic worker is introduced and what’s the usage?
Polly
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2 answers
How to import csv whose time data is in the format of “M-d-y h-m”?
The sample data from csv is shown as follows:
datetime
symbol
price
volume
10/1/2020 9:00
XYZ
10.68
375
10/1/2020 9:00
XYZ
10.9
66
10/1/2020 9:00
XYZ
11.42
103
10/1/2020 9:00
XYZ
12.62
280
10/1/2020 9:00
XYZ
10.73
23
10/1/2020…
dbaa9948
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1 answer
How to import a large CSV file whose size is about 300GB?
I have a large CSV file whose size is about 300GB. I want to know how to import it into DolphinDB.
n=10000000
dataFilePath="/home/jwu/data/dhbt.csv"
table(10000:0,`id`time`v`q,[SYMBOL,TIMESTAMP,DOUBLE,DOUBLE])
//Create table structure
login(`…
jinwandalaohu
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votes
1 answer
Switching nodes in High Availability mode
I repeatedly switch data nodes in high availability mode, the terminal continues prompting that the transaction is occupied, and then resumes after a few minutes. Why does this occur?
Polly
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votes
1 answer
How to automatically record the arrival timestamp when the data arrives into the database
In the GUI, when adding data, I can use timestamp(now()) to generate it. But what if I send data through the c++ API? How to generate the timestamp when it arrives in the database, instead of sending it over after it is generated on the c++ client.…
dbaa9948
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2 answers
Does dolphindb have a development plan to support embedded list as a column in a table?
Is there any development plan by dolphindb to support embedded list as a column in a table? we need something like the followings:
1. We quickly calculate the cumulative ask/bid qty according to the orderbook and save it to a column.
2. According…
damie
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How to count the proportion of NULL values in the matrix?
Take an example: my metric is like this:
col1
col2
col3
1
4
7
2
6
9
How to count the proportion of NULL values in the above matrix?
winnie
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