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InfluxDB Line Protocol

Introduction​

In the InfluxDB Line protocol format, a single line of text is used to represent one row of data. Each line contains 4 parts as shown below.

measurement,tag_set field_set timestamp
  • measurement will be used as the name of the STable Enter a comma (,) between measurement and tag_set.
  • tag_set will be used as tags, with format like <tag_key>=<tag_value>,<tag_key>=<tag_value> Enter a space between tag_set and field_set.
  • field_setwill be used as data columns, with format like <field_key>=<field_value>,<field_key>=<field_value> Enter a space between field_set and timestamp.
  • timestamp is the primary key timestamp corresponding to this row of data

For example:

meters,location=California.LosAngeles,groupid=2 current=13.4,voltage=223,phase=0.29 1648432611249500
note
  • All the data in tag_set will be converted to NCHAR type automatically
  • Each data in field_set must be self-descriptive for its data type. For example 1.2f32 means a value 1.2 of float type. Without the "f" type suffix, it will be treated as type double
  • Multiple kinds of precision can be used for the timestamp field. Time precision can be from nanosecond (ns) to hour (h)
  • The rule of table name
    • The child table name is created automatically in a rule to guarantee its uniqueness.
    • You can configure smlAutoChildTableNameDelimiter in taos.cfg to specify a delimiter between tag values as the table names. For example, you set smlAutoChildTableNameDelimiter=- in taos.cfg, when you insert st,t0=cpu1,t1=4 c1=3 1626006833639000000, the child table will be cpu1-4
    • You can configure smlChildTableName in taos.cfg to specify a tag value as the table names if the tag value is unique globally. For example, if a tag is called tname and you set smlChildTableName=tname in taos.cfg, when you insert st,tname=cpu1,t1=4 c1=3 1626006833639000000, the child table cpu1 will be created automatically. Note that if multiple rows have the same tname but different tag_set values, the tag_set of the first row is used to create the table and the others are ignored
  • It is assumed that the order of field_set in a supertable is consistent, meaning that the first record contains all fields and subsequent records store fields in the same order. If the order is not consistent, set smlDataFormat in taos.cfg to false. Otherwise, data will be written out of order and a database error will occur.(smlDataFormat in taos.cfg default to false after version of 3.0.1.3, smlDataFormat is discarded since 3.0.3.0)

For more details please refer to InfluxDB Line Protocol and TDengine Schemaless

Examples​

package com.taos.example;

import com.taosdata.jdbc.SchemalessWriter;
import com.taosdata.jdbc.enums.SchemalessProtocolType;
import com.taosdata.jdbc.enums.SchemalessTimestampType;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class LineProtocolExample {
    // format: measurement,tag_set field_set timestamp
    private static String[] lines = {
            "meters,location=California.LosAngeles,groupid=2 current=11.8,voltage=221,phase=0.28 1648432611249000", // micro
                                                                                                              // seconds
            "meters,location=California.LosAngeles,groupid=2 current=13.4,voltage=223,phase=0.29 1648432611249500",
            "meters,location=California.LosAngeles,groupid=3 current=10.8,voltage=223,phase=0.29 1648432611249300",
            "meters,location=California.LosAngeles,groupid=3 current=11.3,voltage=221,phase=0.35 1648432611249800",
    };

    private static Connection getConnection() throws SQLException {
        String jdbcUrl = "jdbc:TAOS://localhost:6030?user=root&password=taosdata";
        return DriverManager.getConnection(jdbcUrl);
    }

    private static void createDatabase(Connection conn) throws SQLException {
        try (Statement stmt = conn.createStatement()) {
            // the default precision is ms (millisecond), but we use us(microsecond) here.
            stmt.execute("CREATE DATABASE IF NOT EXISTS test PRECISION 'us'");
            stmt.execute("USE test");
        }
    }

    public static void main(String[] args) throws SQLException {
        try (Connection conn = getConnection()) {
            createDatabase(conn);
            SchemalessWriter writer = new SchemalessWriter(conn);
            writer.write(lines, SchemalessProtocolType.LINE, SchemalessTimestampType.MICRO_SECONDS);
        }
    }
}

view source code

Query Examples​

If you want query the data of location=California.LosAngeles,groupid=2, here is the query SQL:

SELECT * FROM meters WHERE location = "California.LosAngeles" AND groupid = 2;