query

Documentation

Overview

Package query provides functions to transform queries.

Index

• Variables
• func Fingerprint(q string) string
• func Id(fingerprint string) string

Examples

• Fingerprint

Variables

var Debug bool = false

Debug prints very verbose tracing information to STDOUT.

var ReplaceNumbersInWords = false

ReplaceNumbersInWords enables replacing numbers in words. For example: `SELECT c FROM org235.t` -> `SELECT c FROM org?.t`. For more examples look at test query_test.go/TestFingerprintWithNumberInDbName.

Functions

func Fingerprint

func Fingerprint(q string) string

Fingerprint returns the canonical form of q. The primary transformations are:

• Replace values with ?
• Collapse whitespace
• Remove comments
• Lowercase everything

Additional trasnformations are performed which change the syntax of the original query without affecting its performance characteristics. For example, "ORDER BY col ASC" is the same as "ORDER BY col", so "ASC" in the fingerprint is removed.

Example

package main

import (
	"fmt"

	"github.com/XiBao/db/query"
)

func main() {
	q := "SELECT c FROM t WHERE a=1 AND b='foo'\n" +
		"/* some comment */ ORDER BY c ASC LIMIT 1"
	f := query.Fingerprint(q)
	fmt.Println(f)
}

func Id

func Id(fingerprint string) string

Id returns the right-most 16 characters of the MD5 checksum of fingerprint. Query IDs are the shortest way to uniquely identify queries.