InfluxDB is a time series database used to read and write data at high speed in real time. In this section, you will find information on the following topics,

• To create an InfluxDB

• Salient Points of InfluxDB

• Query Strategy

• Limitation of using InfluxDB

To Create InfluxDB

To create an InfluxDB in Wyn Enterprise, navigate to the Resource Portal and follow the below instructions,

1. Click the + icon and then, select the Create Data Source option.

   
   

2. Select the InfluxDB option from the data source list on the left or from the icon view under the NoSQL section on the right.

   
   

3. Fill in the database configuration information. The database configuration items are described in the table below. Click the Test Connection button to verify the data source connection. Once the connection is tested and validated, you will receive a notification of a successful connection. Click the Create button to finish.

   
   

* Required fields

4. You can view the newly added data source in the Categories tab of the Resource Portal.

Salient Points

1. InfluxDB is a temporal database. Data elements of InfluxDB are listed and described in the following table,

2. The InfluxDB library supporting C# is maintained at the GitHub - influxdb-client-csharp. Note the following,

• The official library supports Flux language and does not support SQL.

• InfluxDB can query data using InfluxQL, Flux, and APIs.

• InfluxQL language is similar to SQL however, it is used only for API query usage.

  InfluxQL and Flux are functionally equivalent. Only the codes of both languages look different. See this help article for more information on the parity of InfluxQL and Flux.

3. Flux is an open-source functional data scripting language. See this help article for more information on Flux language.

4. The following table lists the InfluxDB data types as compared to the C# data types,

5. Connection configurations for InfluxDB: A client can be constructed using a connection string that can contain the InfluxDBClientOptions parameters encoded into the URL.

   connectionString = "http://localhost:8086?token=myToken&org=myOrg")

   Options supported in the connection string are listed and described in the following table,

Note: The timeout supports ms, s, and m as unit. Default value is in milliseconds.

6. InfluxDB supports multi-table queries. When the Flux query results in multiple tables, flatten the data to a single table, the same columns will be merged, and the case of no such column in one table will be filled as null.

7. InfluxDB supports only Native Query Dataset.

Query Strategy

Queries in InfluxDB are performed using the Flux language. For example,

a. Insert the following data into the InfluxDB data source,

PointData.Measurement("measurementName")
    .Tag("location", "west")
    .Field("value", 55D)
    .Timestamp(DateTime.UtcNow.AddSeconds(-10), WritePrecision.Ns);
PointData.Measurement("measurementName")
    .Tag("location", "north")
    .Field("value", 56D)
    .Timestamp(DateTime.UtcNow.AddSeconds(-10), WritePrecision.Ns);
PointData.Measurement("measurementName")
    .Tag("location", "west")
    .Field("value", 57D)
    .Timestamp(DateTime.UtcNow, WritePrecision.Ns);
PointData.Measurement("measurementName")
    .Tag("location", "north")
    .Field("value", 58D)
    .Timestamp(DateTime.UtcNow, WritePrecision.Ns);

b. Now run the following query using the Flux statement,

from(bucket: "bucketName")
    |> range(start: -10m, stop: now())
    |> filter(fn: (r) => r._measurement == "measurementName")

c. Above query will result in two tables. However, the end result will be a single table as listed in the Actual Table below.

Table 1:

Table 2:

Actual Table:

The following are the main considerations of the above result,

1. The _time fields in the two tables are duplicated and the data is not easy to use.

2. Although the structure of the two tables is the same, the representation is different.

3. If the data in both table1 and table2 needs to be used, a more logical solution would be to filter using the filter function.

4. If more than one table exists in the result set returned by InfluxDB, then only the first table will be returned.

5. The returned table will remove the result and table columns because the values of these two columns are not meaningful for the use of the data.

Limitations

Note the following limitation of InfluxDB,

1. Any query that does not return a table is treated as a SQL execution error.

2. When using multi-valued parameters, you must ensure that the first parameter of a multi-valued parameter query returns a table.

3. When a query returns multiple tables, you must ensure that the _value field type is the same for each table.

4. The _value field in multiple tables must be of the same type, otherwise, the data source will report an error.