Writing UDF for Clickhouse using Golang

• ClickHouse

  208 34,153 10.0 C++

  ClickHouse® is a free analytics DBMS for big data

  

Today we're going to create an UDF (User-defined Function) in Golang that can be run inside Clickhouse query, this function will parse uuid v1 and return timestamp of it since Clickhouse doesn't have this function for now. Inspired from the python version with TabSeparated delimiter (since it's easiest to parse), UDF in Clickhouse will read line by line (each row is each line, and each text separated with tab is each column/cell value):

• go.uuid

  4 4,856 0.0 Go

  UUID package for Go

package main import ( "bufio" "encoding/binary" "encoding/hex" "fmt" "os" "strings" "time" ) func main() { scanner := bufio.NewScanner(os.Stdin) scanner.Split(bufio.ScanLines) for scanner.Scan() { id, _ := FromString(scanner.Text()) fmt.Println(id.Time()) } } func (me UUID) Nanoseconds() int64 { time_low := int64(binary.BigEndian.Uint32(me[0:4])) time_mid := int64(binary.BigEndian.Uint16(me[4:6])) time_hi := int64((binary.BigEndian.Uint16(me[6:8]) & 0x0fff)) return int64((((time_low) + (time_mid << 32) + (time_hi << 48)) - epochStart) * 100) } func (me UUID) Time() time.Time { nsec := me.Nanoseconds() return time.Unix(nsec/1e9, nsec%1e9).UTC() } // code below Copyright (C) 2013 by Maxim Bublis // see https://github.com/satori/go.uuid // Difference in 100-nanosecond intervals between // UUID epoch (October 15, 1582) and Unix epoch (January 1, 1970). const epochStart = 122192928000000000 // UUID representation compliant with specification // described in RFC 4122. type UUID [16]byte // FromString returns UUID parsed from string input. // Following formats are supported: // "6ba7b810-9dad-11d1-80b4-00c04fd430c8", // "{6ba7b810-9dad-11d1-80b4-00c04fd430c8}", // "urn:uuid:6ba7b810-9dad-11d1-80b4-00c04fd430c8" func FromString(input string) (u UUID, err error) { s := strings.Replace(input, "-", "", -1) if len(s) == 41 && s[:9] == "urn:uuid:" { s = s[9:] } else if len(s) == 34 && s[0] == '{' && s[33] == '}' { s = s[1:33] } if len(s) != 32 { err = fmt.Errorf("uuid: invalid UUID string: %s", input) return } b := []byte(s) _, err = hex.Decode(u[:], b) return } // Returns canonical string representation of UUID: // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. func (u UUID) String() string { return fmt.Sprintf("%x-%x-%x-%x-%x", u[:4], u[4:6], u[6:8], u[8:10], u[10:]) }

• WorkOS

  workos.com sponsored

  The modern identity platform for B2B SaaS. The APIs are flexible and easy-to-use, supporting authentication, user identity, and complex enterprise features like SSO and SCIM provisioning.

  

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