Golang Clickhouse connector

Create new connection

package main

import (
 ch "github.com/leprosus/golang-clickhouse"
)

var (
    user = "clickhouse.user"
    pass = "clickhouse.pass"
    host = "clickhouse.host"
    port = 8123
    // defaultDatabase is optional and only used if no database is specified
    defaultDatabase = "my-clickhouse-database"
)

func init(){
    conn := ch.New(host, port, user, pass, &defaultDatabase)

    // Also you can preset maximum memory usage limit to execute one query
    conn.MaxMemoryUsage(4 * clickhouse.GigaByte)
}

Query rows

conn := ch.New(host, port, user, pass)

iter, err := conn.Fetch("SELECT `database`, `name`, `engine` FROM system.tables")
if err != nil {
    panic(err)
}

for iter.Next() {
    result := iter.Result

    database, _ := result.String("database")
    name, _ := result.String("name")
    engine, _ := result.String("engine")

    println(database, country, engine)
}

Execute insert

conn := ch.New(host, port, user, pass)

query := fmt.Sprintf("INSERT INTO db.table (SomeFiled) VALUES ('%s')", "Some value")
conn.Exec(query)

Preset you own logging

ch.Debug(func(message string) {
    log.Printf("DEBUG: %s\n", message)
})

ch.Info(func(message string) {
    log.Printf("INFO: %s\n", message)
}

ch.Info(func(message string) {
    log.Printf("WARN: %s\n", message)
}

ch.Error(func(message string) {
    log.Printf("ERROR: %s\n", message)
}

ch.Fatal(func(message string) {
    log.Printf("FATAL: %s\n", message)
}}

Values escaping

value := "Here is tab. This is line comment --"
escaped := clickhouse.Escape(value)
fmt.Print(escaped) //Here\tis tab. This is line comment \-\-

List all methods

Connection

• clickhouse.New(host, port, user, pass) - creates connection
• conn.Attempts(attempts, wait) - sets amount of attempts and time awaiting after fail request (wait in seconds)
• conn.MaxMemoryUsage(limit) - sets maximum memory usage per query (limit in bytes)
• conn.MaxRequests(limit) - sets maximum requests at the same time
• conn.ConnectTimeout(timeout) - sets connection timeout (timeout in seconds)
• conn.SendTimeout(timeout) - sets send timeout (timeout in seconds)
• conn.ReceiveTimeout(timeout) - sets receive timeout (timeout in seconds)
• conn.Compression(flag) - sets response compression

Logging

• clickhouse.Debug(func(message string)) - sets custom logger for debug
• clickhouse.Info(func(message string)) - sets custom logger for info
• clickhouse.Warn(func(message string)) - sets custom logger for warn
• clickhouse.Error(func(message string)) - sets custom logger for error
• clickhouse.Fatal(func(message string)) - sets custom logger for fatal

Fetching

• conn.Fetch(query) - executes, fetches query and returns iterator and error
• conn.ForcedFetch(query) - executes, fetches query and returns iterator and error without requests limits
• conn.FetchOne(query) - executes, fetches query and returns first result and error
• conn.ForcedFetchOne(query) - executes, fetches query and returns first result and error without requests limits
• conn.Exec(query) - executes query and returns error
• conn.ForcedExec(query) - executes query and returns error without requests limits
• conn.InsertBatch(query) - inserts batch data from file into database.table table with TabSeparated, TabSeparatedWithNames, CSV, CSVWithNames format

Iterator

• iter.Next() - checks if has more data
• iter.Err() - returns error if exist or nil
• iter.Result() - returns result
• iter.Close() - closes data stream

Result

• result.Columns() - returns columns list
• result.Exist("FieldName") - returns true if field is exist or false
• result.String("FieldName") - returns string value and error
• result.Bytes("FieldName") - returns bytes slice value and error
• result.Bool("FieldName") - returns boolean value and error
• result.UInt8("FieldName") - returns unsigned int8 value and error
• result.UInt16("FieldName") - returns unsigned int16 value and error
• result.UInt32("FieldName") - returns unsigned int32 value and error
• result.UInt64("FieldName") - returns unsigned int64 value and error
• result.Int8("FieldName") - returns int8 value and error
• result.Int16("FieldName") - returns int16 value and error
• result.Int32("FieldName") - returns int32 value and error
• result.Int64("FieldName") - returns int64 value and error
• result.Float32("FieldName") - returns float32 value and error
• result.Float64("FieldName") - returns float64 value and error
• result.Date("FieldName") - parses data YYYY-MM-DD and returns time value and error
• result.DateTime("FieldName") - parses data YYYY-MM-DD HH:MM:SS and returns time value and error

Escaping

• clickhouse.Escape("ValueToEscape") - escapes special symbols
• clickhouse.Unescape("ValueToUndoEscaping") - undoes escaping of special symbols