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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2 answers
DolphinDB: Character count in a string
How to return the number of a specified character in a String, such as the number of comma in the following String:
"Aasd,LLLL,xxx"
Smalllpotatoo1
- 173
- 5
1
vote
1 answer
Nodes fail to start due to errors in loading scheduled tasks
In both standalone server and single-machine cluster modes, an error is reported when nodes are started, which is shown as follows:
Failed to unmarshall the job [..]. Can't recognize function zmq::getSubJobStat. Invalid message format
I used the…
winnie
- 183
- 1
- 6
1
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1 answer
How to convert a column of a table into a tuple?
Here is a table and I want to update the column with the following script.
init=array(DOUBLE, 0) val
t=table(1..5 as id, `a`a`b`b`c as sym, 2022.01.01 + 1..5 as date, [1.0, 2.0, 3.0, 4.0, 5.0] as val)
update t set v=accumulate(def(a,…
dbaa9948
- 189
- 2
- 10
1
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1 answer
DophinDB Kafka plugin: cannot read data from Kafka topic
I subscribed a Kafka topic with only one partition. I want to read the data, but failed, is there something wrong?
My script is as follows:
brokerList = "....."
groupId = "Test001"
topics=["TEST1"]
consumerCfg = dict(string,…
winnie
- 183
- 1
- 6
1
vote
1 answer
Failed to import data to a stream table containing array vectors with DolphinDB Python API
The following script defines a stream table where the column “askPrice“ and “bidPrice“ are array vectors of DOUBLE type.
share streamTable(
10000:0,
`time`sym`askPrice`bidPrice,
[DATETIME,SYMBOL,DOUBLE[],DOUBLE[]]
) as…
Claire
- 238
- 4
1
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1 answer
DolphinDB - Fill missing values of a sequence
I have a table t
t=table(100 101 103 106 as price,take(10,4) as n)
price n
100 10
101 10
103 10
106 10
For the missing values of the column price, like 102, 104, and 105, I want to fill it with n=0.
price n
100 …
jinwandalaohu
- 226
- 1
- 7
1
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1 answer
Automate function execution with a loop using metaprogramming
How can I automate the execution of a series of functions (with the names “test_1”, “test_2“, … “test_100”) using metaprogramming in DolphinDB?
For example:
def test_2(){
return 1
}
eval()//output: 1
I want to use a loop to generate…
jinwandalaohu
- 226
- 1
- 7
1
vote
1 answer
How to obtain the last n rows of high-frequency tick data in an efficient way?
I have an in-memory table with 3 million records.
Part of the stock data is as follows:
How can I quickly get the last n rows of this table, say 35,000 rows?
Polly
- 603
- 3
- 13
1
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1 answer
Generate a sequence of records from a base record
Is there a way to expand table 1 into table 2? It is to output each integer between start_no and end_no as a seq_no field, and take the other fields of the original table to form a new table (table 2).
Table 1:
date source market channel_no…
Polly
- 603
- 3
- 13
1
vote
1 answer
Timestamp inserted in DolphinDB does not match expectations
The timestamp I insert is timestamp(1656898205942), which should be 2022/7/4 9:30:5.942. However, in DolphinDB it shows 2022/7/4 1:30:5.942. It looks like a time zone problem. Can anyone tell me how to obtain the expected timestamp？
YaN
- 407
- 1
- 6
1
vote
1 answer
How does sortKeyMappingFunction works in DolphinDB?
As I learn from DolphinDB help, parameter sortKeyMappingFunction of function createPartitionedTable is used to reduce the dimensionality of sort keys. I wonder when and why is the dimensionality reduction needed?
Polly
- 603
- 3
- 13
1
vote
1 answer
assign the READ privilege to userGroup1 of 4 tables in a DolphinDB database
I have many databases created. I want to assign to userGroup1 the READ privilege to 4 tables out of the total of 6 tables in the database db1. How can I use grant to specify the usergroup and tables?
Polly
- 603
- 3
- 13
1
vote
1 answer
convert the time columns to DolphinDB TIME when importing live market data
When importing a CSV file containing live market data to DolphinDB, how to convert the time columns to the DolphinDB TIME type time in DolphinDB? For example, the csv file contains a time value 093000000 which will be parsed as a string if I import…
Eva Gao
- 402
- 1
- 7
1
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1 answer
Get the records with a certain name from hash partitions in DolphinDB
My table is hash partitioned on the “name” column. I want to retrieve all records with a certain name value from all the partitions. Any DolphinDB functions to fulfill it?
Polly
- 603
- 3
- 13
1
vote
1 answer
DolphinDB error report: Connection refused
The error is raised every time when I try to select based on multiple conditions. The code I'm using is:
tb=loadTable("dfs://min","min_kline")
m=select date, code, "m_h_0931_1451" as name, max(high_min) from tb where date(dt)>=2008.01.01 and…
Nicai Nolmen
- 11
- 1